UNIVERSITY OF BATH

DEPARTMENT OF MECHANICAL ENGINEERING

DESIGN AND DEVELOPMENT OF A MEDICAL

DEVICE TO IMPROVE THE ASSEMBLY OF

HEAD/NECK TAPER JUNCTIONS IN MODULAR

TOTAL HIP REPLACEMENTS

Submitted by Robin Maguire

For the Degree of MSc Engineering Design

September 2013

COPYRIGHT

Attention is drawn to the fact that copyright of this dissertation rests with the

author. This copy of the dissertation has been supplied on condition that

anyone who consults it is understood to recognise that its copyright rests with

its author and that no quotation from this dissertation and no information

derived from it may be published without the prior written consent of the

author.

This dissertation may be available for consultation within the University

Library and may be photocopied or loaned to other libraries for the purpose of

consultation.

CHEATING AND PLAGIARISM

“I  certify  that  I  have  read  and  understood  the  entry   in  the  Student  Handbook  

on Cheating and Plagiarism and that all material in this assignment is my own

work, except where I have indicated with appropriate references.

Name: Robin Maguire

Student Number: 129399661

Signed: ___________________ Date:_______

ABSTRACT

There has been a significant failure rate in modular total hip replacements

(MTHR) over the past few years, particularly with the use of large diameter

Metal on Metal (MoM) bearings. Various studies have shown that sub-optimal

strength of the head-neck taper junction plays an important role in these high

failure rates.

The purpose of this project is to design and develop a medical device to

improve the assembly of this taper junction with an overall aim to reduce the

occurrence of early revision surgeries on MTHRs. The device aims to ensure

axial alignment of the head and neck tapers before providing an adjustable

impact force between 4KN and 6KN to achieve the strongest possible junction

assembly, with the target of reducing the incidence of fretting and corrosion at

this junction and its associated problems.

User-Needs and Design requirements for this device were established

thought an in depth investigation of relevant literature. From this investigation

a Product Design Specification (PDS) was produced and a final concept

generated, based on these requirements. A Testing Rig was then developed

and manufactured as a proof-of-concept for the impact delivery system

proposed in the final design. Testing and evaluation using this Rig provided

useful data emphasising the effect of tip material selection on the impulse

force produced by the Testing Rig. This project has resulted in the

development of a device design capable of improving the strength of

head/neck taper junctions in MTHRs. It has also resulted in the manufacture

of a lab testing rig which can be used again in the future to further aid the

development of this design.

2

CONTENTS

1. INTRODUCTION 1

1.1 What is a Total Hip Replacement? 1

1.2 What are THRs used to treat? 2

1.3 What is a Modular Total Hip Replacement? 3

1.4 Why are they Modular? 4

1.5 How are MTHRs implanted? 4

1.6 How are MTHR assembled? 5

1.8 What is the problem effecting MTHR? 6

2. AIMS AND OBJECTIVES 8

3. LITERATURE REVIEW 9

3.1 Understanding the problem and why it is occurring 9

3.2 How to reduce or eliminate the problem 12 3.2.1 What influence do Manufacturers have on the assembly? 12 3.2.2 What influence do Surgeons have on the assembly? 15

4. USER NEEDS & DESIGN REQUIREMENTS 24

4.1 Fundamental Design Requirements 26

4.2 Establishing and Defining User Needs 27

4.3 Product Design Specification 33 4.3.2 Commercially available designs and patent research 35 4.3.1 Medical device standards review 38

3

4.3.2 Generation of PDS 39

5. DEVELOPMENT & EVALUATION 40

5.1 Concept Generation and Evaluation 40 5.1.1 Initial Product Design Specification (PDS) 41 5.1.2 Discretisation of Design Challenge 42 5.1.3 Radial Thinking 43 5.1.4 Visual Concept Analysis 44 5.1.5 Critical Assessment and Selection 52 5.1.6 Further Investigation of Powering Concept 55 5.1.7 Development of Final Powering Concept 60 5.1.8 Mechanical Feasibility of Chosen Concept 67 5.1.9 Development of Proof-Of-Concept Testing Rig 73

5.2 Detailed Design 79 5.2.1 Solid Modelling 79 5.2.3 Draft Drawings 80 5.2.4 Manufacturing 80

6. TESTING 81

6.1 Calibration of the Load Cell 81

6.2 Rig Testing 83 6.2.1 Procedure 84 6.2.2 Data recorded 87

7. RESULTS AND DISCUSSION 92

7.1 Evaluation of Instron Data 92

7.2 Evaluation of Load Cell Data 93

7.3 Evaluation of Testing Rig 95

4

7.4 Discussion 95

8. CONCLUSIONS 96

10. REFERENCES 98

11. APPENDICES 101

5

NOMENCLATURE

N = Newtons

KN = Kilo Newtons

F = Force

m = Mass

g = acceleration due to gravity (9.81m/s)

m/s = meters per second

Kg = Kilograms

t = Time (in seconds)

Δt = Impact duration

v = Velocity

Δv = change in velocity

k = Spring Stiffness (in N/m)

ABBREVIATIONS

THR = Total Hip Replacement

MTHR = Modular Total Hip Replacement

MoM = Metal on Metal

CoC = Ceramic on Ceramic

CoM = Ceramic on Metal

UHMWPE = Ultra High Molecular Weight Polyethylene

PDS = Product design specification

LIST OF FIGURES AND TABLES

FIGURES

Figure 1: Illustrated Hip Replacement; Before and After [2] ....................................... 1

Figure  2:  Charnley’s  Low  Friction  Arthroplasty  [4] ..................................................... 2

Figure 3: Illustration of Normal Vs. Arthritic Hip [5] .................................................... 3

Figure 4: Exploded View of MTHR Assembly [7] ....................................................... 3

Figure 5: Illustration of MTHR Surgical Procedure [11] .............................................. 4

Figure 6: Orthopaedic Mallet and Impactor [12] ......................................................... 6

Figure 7: Example of matched and mismatched taper angles [20] .......................... 13

Figure  8:  Stuart  Pugh’s  Design  Process  Model  [33] ................................................. 25

Figure 9: Orthopaedic Surgeon Survey Introduction ................................................ 28

Figure 10: Surgeon Survey, Q1 ............................................................................... 28

Figure 11: Surgeon Survey, Q2 ............................................................................... 29

Figure 12: Surgeon Survey, Q3 ............................................................................... 30

Figure 13: Surgeon Survey, Q4 ............................................................................... 30

Figure 14: Surgeon Survey, Q5 ............................................................................... 31

Figure 15: Surgeon Survey, Q6 ............................................................................... 31

Figure 16: Surgeon Survey, Q7 ............................................................................... 32

Figure 17: Surgeon Survey, Q8 ............................................................................... 32

Figure  18:  Stuart  Pugh’s  Design  Core  [33] .............................................................. 34

Figure 19: Controlled Force Hammer [35] Figure 20: Controlled Force

impacting device [36] ....................................................................................... 35

Figure 21: Handling Device for Hip Implant [37] Figure 22: Hip Joint Prosthesis

and Fitting Tool [38] ......................................................................................... 35

2

Figure 23: Device for Handling Hip joint Heads [39] Figure 24: Head

holder and impactor [40] .................................................................................. 36

Figure 25: Method of applying Femoral head Resurfacing [41] Figure 26: Nail

gun Patent 1 [42] ............................................................................................. 36

Figure 27: Nail gun Patent 2 [43] Figure 28: Wire Shelf

Driver [44] ........................................................................................................ 36

Figure 29: Automatic Centre Punch [44] .................................................................. 37

Figure 30: Inserter jaw for knee prosthesis impaction and extraction [45] ................ 37

Figure 31: Comparison in grading between EU and USA Device Classification [48] 38

Figure 32: Initial sketch to capture ideas ................................................................. 42

Figure 33: Development of Objective B ................................................................... 43

Figure 34: Development of Objective C ................................................................... 44

Figure 35: Three Prong Flexible Support and Centring Cone Sketch ...................... 45

Figure 36: Semi-Cup + Centring Cone Sketch ......................................................... 45

Figure 37: Bent Hex-Rod Sketch ............................................................................. 46

Figure 38: Bent Rod Circular Profile Sketch ............................................................ 46

Figure 39: Split Cup/Split Mould Sketch .................................................................. 47

Figure 40: Slide Hammer - Direct Impact Sketch ..................................................... 47

Figure 41: Slide Hammer - To Charge Spring Sketch .............................................. 48

Figure 42: Magnets Sketch ...................................................................................... 48

Figure 43: Electro-Magnets Sketch ......................................................................... 49

Figure 44: Screw Mechanism - No Impact Sketch ................................................... 49

Figure 45: Screw Mechanism - To Charge Spring Sketch ....................................... 50

Figure 46: Lever - To Charge Spring Sketch ........................................................... 50

Figure 47: Pneumatic Piston Sketch ........................................................................ 51

Figure 48: Rod Inserted In Stem Hole Sketch .......................................................... 51

Figure 49: Mechanism to Hook around the Lips at Base Sketch .............................. 52

Figure 50: Pneumatic Nail Gun Illustration [49] ........................................................ 56

3

Figure 51: The Solenoid Powered Nail Gun [49] ...................................................... 57

Figure 52: Electric Powered Nail Gun [49] ............................................................... 58

Figure 53: Can-Crushing Device [50] ...................................................................... 59

Figure 54: Adapted Juicer Sketch ............................................................................ 60

Figure 55: Adapted Can Crusher Sketch ................................................................. 61

Figure 56: Corkscrew Lever System Sketch ............................................................ 62

Figure 57: Twisting Adjustment and Release Concept Sketch ................................. 63

Figure 58: Gearbox Style Spring Compression Adjustment Concept Sketch ........... 63

Figure 59: Spring Compression adjustment System Sketch .................................... 64

Figure 60: Slotted Trigger Release Mechanism Sketch ........................................... 65

Figure 61: Firearm Trigger Concept Sketch ............................................................. 65

Figure 62: Handle Trigger System Sketch ............................................................... 65

Figure 63: Final Developed Concept Sketch ........................................................... 66

Figure 64: Tubular Casing Surrounding Spring Sketch ............................................ 67

Figure 65: 3 step sketch illustration of corkscrew charging method ......................... 67

Figure 66: Force Balancing Free Body Diagram ...................................................... 68

Figure 67: Instron Loading Machine [51] ................................................................. 74

Figure 68: Initial Testing Rig .................................................................................... 75

Figure 69: Simplified Concept for Testing Rig .......................................................... 76

Figure 70: Initial Lever Design ................................................................................. 77

Figure 71: Lever Design Development .................................................................... 78

Figure 72: Final Lever Design ................................................................................. 78

Figure 73: Final Assembled SolidEdge 3D Model .................................................... 79

Figure 74: First Calibration Test plot of Voltage Vs. Time ........................................ 82

Figure 75: Load Cell Calibration Test Data Plotted on Graph .................................. 83

Figure 76: Custom Mounting points, close up view of top, close up view of bottom . 84

Figure 77: Spring Section in mounting points, close up view of top, close up view of

bottom ............................................................................................................. 85

4

Figure 78: Base plate fixed to table with and without Rubber Base ......................... 86

Figure 79: Table of Data recorded from Instron ....................................................... 88

Figure 80: Test 2, Steel, 2KN (with rubber base) ..................................................... 89

Figure 81: Extrapolated Load Cell Data, >2KN ........................................................ 90

Figure 82: Extrapolated Load Cell Data, 4KN and 6KN ........................................... 91

Figure 83: Images of Failed PVC and Rubber Tips at 4KN Load ............................. 92

TABLES

Table 1: Data from Pennock et al. (2002) study [29], [10] ........................................ 17

Table 2: Data from Lavernia et al. (2009) Study [30], [10]........................................ 18

Table 3: Data from Heiney et al. (2009) Study [31], [10] .......................................... 19

Table 4: Data from Rehmer et al. (2012) Study [32], [10]......................................... 21

Table 5: Initial PDS.................................................................................................. 41

Table 6: Scoring Table for Sub-System Concepts ................................................... 54

Table 7: Data recorded during Load Cell Calibration ............................................... 82

1

1. INTRODUCTION

1.1 What is a Total Hip Replacement?

There are two types of Hip Replacement surgery, Hip Resurfacing and Total Hip

Replacement (THR). This project focusses on the THR procedure, which is also

known as Total Hip Arthroplasty. THRs are among the most common orthopaedic

procedures performed today [1]. The THR procedure involves removing the femoral

head (top of the thigh bone) and a layer of bone from in and around the acetabulum

(hip socket) and replacing them with artificial materials, thus resulting in an artificial

hip joint. The before and after pictures of a hip joint that has undergone a THR is

shown in Figure 1 [2] below, with the original diseased hip joint shown on the left

and the new replacement joint shown on the right.

Figure 1: Illustrated Hip Replacement; Before and After [2]

2

The first modern THRs were designed by John Charnley in the 1960s, which

stemmed from his paper   “Surgery   of   the   Hip   Joint   - present and future

developments” [3] published in 1960.  Charnley’s  THR consisted of a high density

polyethylene cup that was fixed inside the hip joint socket and a stainless steel

component that made up the artificial femoral head and stem which slotted into the

patient’s femur. This   “low   friction  arthroplasty” [4] hip design was first implanted in

November 1962 and can be seen in Figure 2 [4] below.

Figure 2: Charnley’s  Low  Friction  Arthroplasty [4]

1.2 What are THRs used to treat?

THRs can be used to treat degenerative arthritis in the hip joint and can also be

used to treat femoral neck fractures [1]. The original hip joint shown previously in

Figure 1 [2] is arthritic, as you can see the deterioration of the bone at the

ball/socket contact point. This is shown in more detail in Figure 3 below [5] where

illustrations show the difference between and healthy and arthritic hip joint.

3

Figure 3: Illustration of Normal Vs. Arthritic Hip [5]

1.3 What is a Modular Total Hip Replacement?

Modular THRs (MTHR) were introduced in the 1970s [6]. The previous leg (femoral)

component used in Charnley’s   original   design  was   separated into head and stem

components and the previous plastic cup was separated into shell and liner

components. An example of such a modern modularised THR design is shown in

Figure 4 [7], as follows, using an exploded view of an assembly.

Figure 4: Exploded View of MTHR Assembly [7]

4

1.4 Why are they Modular?

Modularisation was introduced into the design of THRs in the 1970s [8] to allow

more flexibility in material selection/combination and component sizing to ensure a

more individually suited THR for each patient. It also allows surgeons to reduce

inventory [9] and simplifies revision surgeries [8]. Several different material choices

and combinations are available to surgeons. For the stem and head; Cobalt Chrome

or Ceramic Heads can be used on Titanium stems. For the bearing combinations;

Metal on Metal (MoM), Ceramic on Ceramic (CoC) and Ceramic on Metal (CoM),

and finally Ceramic or Metal heads can also be used on Ultra High Molecular

Weight Polyethylene (UHMWPE). [10]

1.5 How are MTHRs implanted?

The MTHR procedure is illustrated in four steps in Figure 5 as follows.

Figure 5: Illustration of MTHR Surgical Procedure [11]

5

Step A involves making an incision to gain access to the joint area and dislocating

or  “disarticulating”  [11] the femoral head from the acetabulum (or hip socket).

Step B involves cutting off the femoral head with a surgical saw.

Step C involves reaming out the acetabulum and the femur to prepare them to

receive the shell and stem respectively.

Step D involves the introduction of the prosthetic components and the final image in

the bottom right hand side of the figure shows the fully installed THR.

1.6 How are MTHR assembled?

The order in which the components are introduced in this procedure is important to

note. The acetabulum shell is first introduced and fixed in place before the stem is

inserted into the femur. There are two types of stem designs; cemented, where

special cement is inserted into the reamed femur before the insertion of the stem

which is then used to permanently fix the stem in the femur; and cement-less, where

the surface finish on the stem is designed to encourage bone growth and adhesion

to the stem. Once the shell and stem have been introduced, the surgeon can then

trial their proposed head and liner size using special trial head and liner

components. Once these trial components have been fitted and the head (already

fitted to the stem) has been located in the hip socket (liner), the surgeon can then

check the fit of the joint in the patient by checking leg length and the range of motion

available. Once the surgeon is happy with the proposed size of their head and

associated liner the trial versions are removed and the exposed shell cup and stem

taper surfaces are cleaned to prepare them for the introduction of the final head and

liner components. The liner is inserted and fixed in place before the head is placed

on what is called the neck taper of the stem and the head is then impacted onto the

6

stem taper using a mallet and impactor (usually tipped with a softer material than

the head so as not to damage the surface of the head). An example of the sort of

mallet and impactor commonly used is shown in Figure 6 [12] below.

Figure 6: Orthopaedic Mallet and Impactor [12]

The male neck taper on the stem is cone shaped. This taper is designed to match a

female taper on the inside of the femoral head component. When the head is

impacted onto the neck the taper, the head taper must expand as it is forced down

the neck taper by the impact delivered by the surgeon. This increases surface

friction and creates hoop stresses that fix the two components firmly in place.

1.8 What is the problem effecting MTHR?

However, it is this particular junction which has been the focus of much research

and analysis over the past few years and is gaining more and more attention. MTHR

have long been associated with earlier than expected revision surgeries and many

7

product recalls. Large diameter (>36mm) MoM bearings are by far the worst

offenders when it comes to early revisions and product recalls. The use of large

diameter MoM bearings amplifies an existing issue regarding the strength of the

head/neck taper junction more so than other joint material and geometry selections.

Large diameter bearings produce an increase in the torque in the joint, as a larger

frictional torque is generated since there is a longer lever arm acting between the

fulcrum or centre of the joint’s rotation and the surface where the head makes

contact with the liner, especially MoM. This increase in force about the junction,

leads to increased levels of fretting wear and corrosion, which causes the liberation

of prosthesis material and hence early revision surgeries (as the human body has

an adverse reaction to the presence of these foreign particles).

Fretting corrosion and wear can still occur in all material and geometry combinations

but the accelerated and extreme instances found in some of the large diameter

MoM bearings, have really highlighted this problem and raised its importance in all

MTHR designs.

Various studies, which will be discussed in the next section, have shown that the

main factor affecting the longevity of MTHRs is the strength of the head/neck taper

junction. The main influence on the assembly of this junction is the magnitude of the

impact force applied during assembly.

The next section of this report lays out the aims and objectives of this project in a

clear and concise manner.

8

2. AIMS AND OBJECTIVES

Aim: To design and develop a medical device to improve the assembly of

head/neck taper junctions in MTHRs with an overall aim to contribute to the

reduction of early revision surgeries for MTHRs

Objectives:

1. Review relevant literature to gain greater understanding/scope of problem

2. Establish User Needs and Design Requirements

3. Produce Product Design Specification (PDS)

4. Generate and evaluate design concepts

5. Design and develop a prototype for proof-of-concept

6. Manufacture and Test prototype

7. Evaluate test results and review overall concept

9

3. LITERATURE REVIEW

This section of the report contains the findings from the literature review carried out

on the failure of MTHRs due to head/neck taper junctions. The review spread out

beyond the borders of this specific issue to ensure an understanding of the bigger

picture could be taken into account before focussing on the specific problem itself

towards the end of the review. The findings are now presented under two headings,

“Understanding  the  Problem and why it is occurring”, followed by “How to reducing

or eliminate the  problem”.

3.1 Understanding the problem and why it is occurring

Before trying to solve the problem it is essential to take the time to fully understand

the background and history of the problem and the reason behind its occurrence.

One of the most renowned examples in the failure of large diameter MoM MTHR

was the Depuy ASR. Five hundred and five Depuy ASR MTHRs were implanted in

total [13]. They were found to have an extremely high failure rate of 48.8% after six

years [13]. The design was found to have failed for two reasons, and Heneghan et

al. (2012) [14] made an important connection between the ASRs design failings and

other existing designs that are still being used today. The first reason for the failure

of the ASR was due to the acetablular cup being too shallow. This led to wear at the

bearing edges and hence starvation of lubrication in the bearing area which led to

increased wear around the edges of the cup, thus creating a self-destructive cycle.

The wear causes the liberation of metal particles from the bearing surfaces which

cause   “extensive   soft   tissue   necrosis   and   disruption   of   bone” [14]. The second

failure reason, which is the most relevant to this project, was due to the increased

torque experienced at the head/neck taper junction which was caused by the larger

10

diameter of the bearing. This increase in torque caused wear and fretting corrosion

which again led to the liberation of metal particles and thus patient complications, as

with the first failure method. The reason why the second failure method is the most

important to this project is because the use of large diameters in MoM bearings is

not unique to the ASR design and so plays a role in the failure rates of various other

MTHR designs. Both Henghan et al. (2012) [14] and Langton et al. (2011) [13]

agree on this point and Langton et al. go on to suggest that bearing diameters of

36mm or greater are most at risk to this failure method.

Smith et al. (2102) [15] concluded, following an in depth analysis of National Joint

Registry Data covering England and Wales, that MoM bearings are more likely than

other bearing material combinations to fail, and also found that their failure rates

were increasing proportional to increasing bearing diameter size. Langton et al.

(2011) [13] also came to the same conclusion in their study into the failure of the

Depuy AST MTHR thus adding further backing to this theory.

The UK government, by way of the Medicines and Healthcare Products Regulatory

Agency (MHRA), took action on the issue by releasing a Medical Device Alert

(MDA/2012/036) [16]. This MDA provided instructions on monitoring patients with

MoM Hip Replacements (or Hip Resurfacings), and highlighted the dangers

associated with the use of the Depuy ASR models which had been recalled.

Smith et al. (2012) suggested in his study on the Joint Registry data that the

increased failure rates for Large Diameter MoM bearings could be due to the

loosening of the head/neck taper junction caused by the increased torque acting

about that junction, which was also suggested by Heneghan et al. (2012) [14], as

mentioned earlier. Bishop et al. (2008) [17] carried out a study into the frictional

moments in MTHRs and found that MoM bearing combinations produced the

11

greatest frictional moments followed by Metal on UHMWPE and then CoC with the

lowest frictional moments, thus adding to the growing evidence pointing at the

failings of MoM bearings. Langton et al. (2011) [13] found that as the trend in

increasing bearing diameter grew, there was no increase in the diameter of the neck

taper to counter the associated increase in torque. In a different study by Langton et

al. (2012) [18] they noted that neck diameters actually decreased as larger and

larger bearings sizes became available, thus exacerbating the problem. The

reasoning behind reducing the diameter of the neck taper was to increase the range

of motion of the prosthesis.

One of the biggest studies of MTHR neck/taper junctions was carried out by

Goldberg et al. (2002) [19] and looked into various different aspects and failure

methods in this junction. One of the recommendations that they put forward

following their research was to increase the neck taper diameter with an aim to

increasing the stiffness of the neck so as to reduce the fretting and corrosion that

they found to be occurring at this junction.

To summarise, the importance of the strength of the head/neck taper junction has

been highlighted by the recent failing of some designs of MTHRs (example Depuy

ASR). These designs have increased the head diameter to reduce the occurrence of

dislocations of the head in the hip socket, and reduced the neck taper diameter to

increase the range of motion in the joint, but have actually increased the torque

about the bearing, which has a loosening effect on the head/neck taper junction.

This loosening allows micro-motions in the junction, which then leads to fretting

wear and corrosion. The fretting wear and corrosion causes the liberation of taper

material particles which are toxic to the human body and produce patient

complications that are treated with revision surgeries.

12

Now that the severity and reasoning behind the failure MTHRs has been established

the next step is to look at who has influence or control over the reduction or

elimination of the problem.

3.2 How to reduce or eliminate the problem

This part of the chapter looks at who has control over or influence on the key factors

that contribute towards the strength of the head/neck taper junction. This part

finishes with an in depth analysis of four particularly relevant studies with an aim to

establishing the optimum conditions and provisions for assembling a head/neck

taper junction.

3.2.1 What influence do Manufacturers have on the assembly?

Studies by Langton et al. (2011) [13], Langton et al. (2012) [18] and Goldberg et al.

(2002) [19] have all stressed the importance of the neck taper diameter in ensuring

a strong head/neck taper junction. It must be large enough to provide the neck

stiffness required to support the joint and prevent loosening under high torques.

Manufacturers have control over this dimension, since they are the ones designing

the products. Now that they have been made aware of this factor by the

aforementioned studies they can develop their future designs with this in mind.

Others factors that can influence the strength of this junction are the tolerances

applied during manufacture. For example, it is very important that the head and

neck taper angles are as closely matched as possible for an optimal fit. This is

illustrated in Figure 7 [20] as follows.

13

Figure 7: Example of matched and mismatched taper angles [20]

Figure 7 Part A shows the correct fit with the maximum contact area between the

head and neck tapers. Figure 7 Part B on the right shows a poor fit where there is a

significant taper angle mismatch leaving low contact area creating stress

concentrations and room for micro-motion (also described as toggling) which leads

to fretting corrosion and wear. Goldberg et al. (2002) [19] stressed the importance of

angular mismatch and conicity of the tapers when trying to reduce fretting wear and

corrosion at the head/neck taper junction. They also mention the importance of a

good  quality  surface  finish  or  “roughness”  and  its  effects  on  the  strength  of  the  taper  

junction. Fessler and Fricker (1989) [21] established a connection between the

presence of high hoop stresses in alumina heads and only small levels of taper

angle mismatch. Aside from hoop stress concentrations angular mismatch also

facilitates micro-motion since the taper is not rigidly supporting itself along its length,

as it is only held over a small collar of area (where the stress is concentrated).

Shareef and Levine (1995) [22] confirmed a link between taper angle mismatch

(including general manufacturing tolerances) and micro-motion found in taper

junctions, in their study into this phenomenon. Scharmm et al. (2000) [9] also made

the valid point that the accuracy of machining and the development of better wear-

14

resistant materials plays an important part in the improvement of these designs,

along with the recognition that only a very small mismatch is required to begin a

cycle of fretting corrosion and wear.

In a study which involved measuring the forces required to disassemble three

different model of MTHRs, which had been retrieved from patients undergoing

revision surgeries, Lieberman et al. (1994) [23] made an interesting discovery. One

of the models required a much greater force than the other two to be disassembled

and was the only model type of the three examined not to show any signs of

corrosion after a 78 month period. These particular MTHRs had a different assembly

history from the other two model types in that they had been assembled by the

manufacturer and were supplied to the surgeon in a preassembled condition. These

MTHRs had been shrink fitted with a sealant, applied during this assembly.

Lieberman et al. (1994) [23] believe the greater junction strength and resistance to

corrosion was due to improved manufacturers tolerances and the use of the sealant

during assembly. However, based on the studies in the next part (3.2.2) of this

report, it is suggested that another influence had made the difference in the

assembly. The depth to which the neck would have reached inside the head taper

would have been increased due to the shrink fitting process and no doubt would

have made the junction stronger and hence more difficult to disassemble. In normal

assembly conditions with a surgeon assembling the head and neck tapers at room

temperature, the previous fit could only be replicated with an axially aligned impact

force of optimum magnitude. As mentioned previously the assembly of MTHRs is

carried out in-vivo by a surgeon using a mallet and impactor. The next section

addresses the influence that the surgeons can have on the strength of the

head/neck taper junction.

15

3.2.2 What influence do Surgeons have on the assembly?

The   “fit   of   the   spigot   head”   is   noted   as   the   “most   important   source   of   error”   in  

Fessler   and   Fricker’s   (1989)   [21] study   into   the   “Stresses   in   Alumina   Universal  

Heads   of   Femoral   Prosthesis”.   Bobyn   et   al.   (1994) [24] would agree with their

statement since they found a reduction in taper surface contact area and an

increase in wear and fretting corrosion in two Modular Femoral Prosthesis, after

assembling them both using one fifth of the manufacturers recommended assembly

force and exposing them to the sort of cyclic loading that they would experience in-

vivo. Thus the impact load applied has a significant influence on the fit or the

assembly of the head on the neck. A study carried out by Goldberg and Gilbert

(2003) [25] entitled “In   vitro   corrosion   testing   of   hip   tapers”   concluded that the

“proper  seating  of   the  head  onto   the  neck”   increases  the   forces   required   to  cause  

micro-motion, and hence wear and fretting corrosion. A study by Mroczkowski et al.

(2006) [26] mimicked much of the Goldberg and Gilbert’s (2003) study but added a

sub-study looking at varying the impact applied during assembly and found that, out

of head/neck tapers assembled in air and water and using either hand press

assembly or a 6.7KN impact, the tapers assembled in air using 6.7KN showed the

best resistance to fretting corrosion and wear under cyclic loading. This study again

adds to the proof of the importance of the impact magnitude when trying to prolong

the life of MTHRs in-vivo. However, as much of the previous studies would lead to

the assumption that the greater the impact the better the assembly strength, this is

not the case because if too great a force is used during assembly it can actually

damage the taper interface and cause potentially catastrophic damage to the

femoral head as well as other issues with the interface between the stem and the

femur.

16

The impact force is not the only important factor that the surgeon has influence over

during assembly. The axial alignment when placing the head on the neck taper prior

to impact and the axial alignment of the impact delivered is also extremely

important. Both Callaway et al. (1995) [27] and Pansard et al. (2012) [28] traced

back the failure of a number of MTHRs to incorrect fitting of the head on the neck

taper by examining retrieved MTHRs removed during revision surgeries. They both

found that their retrieved Hip Replacements had failed due to extreme corrosion

caused by incorrect fitting of the head during original assembly. Due to varying

manufacturing tolerances between different brands, it is also strongly recommended

not to mix different manufacturers components as this can result in poorly fitted

parts that can reduce the life of the prosthesis.

Four key papers are now discussed with a focus on the effects of the impact/s

applied during the assembly of the head/neck taper junction with an aim to

establishing the optimum impact magnitude and number of impacts so that this

information can then be used to guide the design of the device that this is being

developed for this project.

The relevant information has been extracted from each of the four studies in an

effort to simplify them for ease of comparison and add clarity to the investigation.

The implant quantities, head diameter, assembly tools, impact forces, number of

impacts and the pull-off forces (forces to pull the assemblies apart) have been used

as the categories by which to analyse these studies. The studies will appear in

chronological order, starting with Pennock et al. (2002) [29] study  entitled   “Morse-

type tapers: factors that may influence taper strength during  total  hip  arthroplasty”.

The relevant data from this study has been populated in the standard table for this

investigation and is shown in Table 1 [10] as follows.

17

Table 1: Data from Pennock et al. (2002) study [29], [10]

This study looks at the effects of varying the magnitude of the impact force, the

order in which the different impact forces are applied and the total number of

impacts delivered during assembly and their effect on the resulting junction strength

(determined by pull-off tests). This study also looked at the effects of wet and dry

taper surfaces on junction strength, but the wetted samples were not included in this

table as Pennock et al. (2002) established that wet taper surfaces reduced the

strength of the junction. However, since the wet tapers were not used, this halved

the size of the data that could be used in Table 1 [10] and hence limited the amount

of data available for use and thus limited the credibility of the data used in the study.

It is also worth noting that the impact forces used were based around an average

force that was found by measuring the impact force applied by a single surgeon

over 11 impacts and came to an average of “2075N”   (N   for   newtons). It can be

assumed   then   that   the   “Medium”   force  magnitude   listed   in   this   study   is   2075N  or  

very   close   to   it,   though   it   is   impossible   to   say   what   magnitude   the   “Light”   and  

“Heavy”  impacts  are.

From the pull-off values shown in Table 1 [10] it can be assumed that the highest

impact provides approximately 95% of the strength to the junction with further lighter

impacts still adding a small contribution (approximately 5%) to the overall strength

18

[29]. Pennock et al. (2002) [29] also states the importance of axial alignment when

delivering the impacts, to ensure that all of the force is transmitted during the

impaction. One of the findings taken from their study (especially when the wet

tapers were taken into consideration) was that they noted an increase in junction

strength with increasing impact magnitude [29].

The next study was carried out by Lavernia et al. (2009) [30] and looked mainly at

the effects of blood and fat contamination on the taper surfaces and the effect they

had on the junction’s   strength. However,   as   they   used   “control”   or   dry   tapers   for  

comparison the data recorded for these was of benefit to this investigation and has

been recorded in Table 2 [10] below.

Table 2: Data from Lavernia et al. (2009) Study [30], [10]

Since this data only covers the control for the main experiment, much like the

previous study, it does not have the largest sample size and this is recognised as a

limitation for the purpose of this investigation. It is also worth mentioning that the

four specimens used were assembled and disassembled 5 times each to establish

an average disassembly, and it is apparent that the repeated assembly and

disassembly of these specimens lowers the strength of the junction and can askew

the average disassembly forces to some degree. The impaction magnitude used in

19

this study can be considered to be a more realistic representation of the average

magnitude of a surgeons impact as they recorded the impact forces applied by 8

different surgeons as opposed to the previous study by Pennock et al. (2002) [29]

that only used 11 impacts by a single surgeon. The result is a 27% (approx.)

decrease of the force used by Pennock et al (2002). It is worth noting that this study

does not vary the impact magnitude or the number of impacts applied, but does give

a good representation of the average pull-off force for the prescribed magnitude with

a single impaction and provides another average value for surgeon impaction

magnitude, which will both be of use later when comparing this study to those that

follow on in this part of the chapter. The overall study showed that a clean and dry

taper provides the optimum assembly condition to facilitate maximum junction

strength.

The next study was carried out by Heiney et al (2009) [31] and had a much larger

sample size of useable data for the population of Table 3 [10] as seen below.

Table 3: Data from Heiney et al. (2009) Study [31], [10]

The average impact force applied  by   surgeon’s  was  also measured for this study

and improved upon the two previous study mentioned, as this time they took values

from 10 surgeons to create the average value to base their range of varied impact

20

assembly forces. The average surgeon’s   impact   force   applied  during  assembly in

this study is roughly twice that of either of the two previous studies showing a large

range of magnitudes arising across the different surgeons used to create the

averages in each study.

Heiney et al. (2009) [31] found there to be a difference in junction strength between

using one impaction and two impactions but found no difference when applying

more than two impactions. This finding compliments one of the findings from the

study by Pennock et al. (2002) [29], in that the first impaction provides the majority

of the junction strength with subsequent impacts providing a small but additional

increase. Heiney et al. (2009) [31] also found that the junction strength increased

along with the impact magnitude thus adding weight to this original finding by

Pennock et al (2002) [29]. It is unfortunate that neither Pennock et al (2002) [29]

nor Heiney et al. (2009) [31] provided the impact forces in newton values instead of

written descriptions such as light, medium and heavy, so that the studies could be

compared in more detail.

Following the completion of their study Heiney et al. (2009) [31] recommended “at  

least two firm,  axially  aligned  blows” to achieve optimum junction strength, but they

also warned that   impacts  of  an   “excessively  high  magnitude”  can   lead   to   “femoral  

fractures around cement-less  stems”, as the impact force may travel down into the

patient during assembly and could damage the bone stem interface.

The next study was carried out by Rehmer et al. (2012) [32] and was the largest and

most relevant to this project. They looked at the effect that different material

combinations, impact magnitudes and the number of impactions can have on the

taper junction strength. One immediate benefit is that they provided the assembly

impact forces in newtons and not in written descriptive terms as in the previous

21

studies. The relevant data acquired from this study is shown in Table 4 [10] as

follows.

Table 4: Data from Rehmer et al. (2012) Study [32], [10]

Using pull-off and twist-off disassembly tests, Rehmer et al. (2012) [32] found that a

single impact of a minimum of 4KN (kilo-newtons) was required to ensure optimum

taper junction strength. They also discovered, just like Heiney et al. (2009) and

Pennock et al. (2002), that there was little or no benefit from more than one

impaction and even went as far as suggesting that more than one impact could

actually loosen the taper junction or reduce the strength provided by a previous

impact.

Rehmer et al. (2012) go on to state that if one single impact of a minimum of 4KN

was set as a recommendation by manufacturers for the assembly of the femoral

prosthesis, then this would place the responsibility on the surgeon to ensure

“suitable   taper   fixation,   by   firm   and   careful   impaction”.   They   state   that   this would

greatly improve the strength of the taper junction in modular femoral prosthesis, but

unfortunately it is clear that this is currently not possible. This is proven in a similar

study by Loch et al. (1994) [8] entitled  “Axial  Pull-Off Strength of Dry and Wet Taper

22

head connections on a modular shoulder prosthesis”. In this study, they use a

surgeon to try to acquire an average assembly impact force for which they can

design a drop rig. The drop rig is then used to assemble their specimens with a

constant impact force but under different conditions (i.e. dry or wet) prior to

disassembly testing. The surgeon assembled 6 shoulder taper junctions using a

mallet and impactor (the same as is used in a modular femoral hip assembly), and

Loch et al. (1994) [8] then measured the force required to pull the joints apart. They

repeated this process with the surgeon and the same six specimens 16 times to

acquire their average pull-off value, which they then used to set a drop rig to

assemble the test specimens to replicate this average pull-off value (under control

conditions). It is acknowledged the average pull-off values may have been affected

by the reduction in strength that can be experienced when repeatedly assembling

and disassembling the same specimens. The pull-off forces, from the surgeon’s  

assemblies, ranged from 958N all the way to 4893N which is a very wide range.

This data on its own would not be enough evidence given the reduced taper junction

strength associated with repeated assembly. However, looking back on each of the

four key studies featured previously it is clear to see that surgeons are not providing

the same magnitudes of impact, and even if they were, the axial alignment of the

impact cannot be guaranteed. So, even if the surgeons could apply an impact force

of no less than 4KN, this could still be diminished if the impact was not axially

aligned with the head and neck tapers, or if the head taper was not seated correctly

on the neck taper prior to impaction. Even though it has not been recorded in the

studies featured here, it seems there is nothing stopping an impaction exceeding

12KN and creating the potential for internal damage to the patient. This prompts the

suggestion that there is need for a device that can help surgeons ensure that the

23

head is correctly seated on the neck taper before providing a single impact of no

less than 4KN, which is axially aligned with the taper axis. The impact should also

not exceed 6KN to ensure that it does not stray into the region where it could cause

internal damage to the patient or damage to the tapers, as mentioned previously.

The findings from this review will be used to guide the design of the device

proposed in this project, and to aid the assembly of MTHRs. The next step in the

process is to establish the user needs and hence design requirements for such a

device.

24

4. USER NEEDS & DESIGN REQUIREMENTS

It is now clear from the Literature Review that there is room for improvement in the

assembly of head/neck taper junctions in MTHRs. This “room for improvement”

grows and becomes a serious problem when considered in the use of large

diameter bearings, particularly MoM bearings. Even if manufacturers applied perfect

tolerances, surfaces finishes and optimum neck taper diameters it is still essential to

correctly assemble this taper junction to benefit from these improvements. It is clear

from the wide ranging impact forces applied by different surgeons that it is unfair to

expect them to be able to repeatedly provide the very specific forces and alignments

required for the optimum assembly of MTHRs using the current tools at their

disposal (mallet and impactor). Therefore the development of a new device is

completely justified.

It is also worth mentioning at this point in the report that the Design Process

Structure being followed in this project is based  loosely  around  Stuart  Pugh’s  Total  

Design Approach (1991) [33].  This   section  of   the   report   is  mimicking   the   “Market”  

stage in Pugh’s  model,  as  shown  in  Figure  8  [33] as follows.

25

Figure 8: Stuart  Pugh’s  Design  Process  Model  [33]

The stage following this will be the development of a Product Design Specification

(PDS) which is referred to in Figure 8 as  “Specification”.  The  “Concept design”  and  

“Detail design” stages feature in the next chapter of this report.

This section of the project involves extracting and clearly defining the design

requirements from the Literature Review. It also includes researching and

investigating other design requirements for the proposed device, with an aim to

26

producing a Product Design Specification (PDS), which can then be used to guide

the next stage of the project.

4.1 Fundamental Design Requirements

These design requirements have been extracted directly from the findings in the

literature review and form the foundation and basis for the entire design, i.e. the

design must achieve all of these requirements to be successful. The fundamental

design requirements are listed as follows.

1. Ensure axially aligned seating of head on neck taper axis prior to impaction

2. Impact must be delivered in axial alignment with neck taper axis

3. Deliver impact force of between 4KN and 6KN, adjustable to 0.5KN

4. Must try to isolate majority of impact to head/neck taper junction

The first requirement is very much self-explanatory and is to try to prevent the

failures recorded by Callaway et al. (1995) [27] and Pansard et al. (2012) [28] as

mentioned previously in the Literature Review.

The second requirement is essential to ensure the efficient transfer of the impact

force into the junction assembly.

The third requirement has also been added from the Literature Review as the device

must now be adjustable to 0.5KN (or 500N). This is to account for the different

manufacturing tolerances and the effect that they will have on the efficient

transmission of the impact force into the taper junction. The adjustability will also be

useful when using different materials, such as ceramic heads, that may require the

27

minimum force, compared to larger metal taper junctions that may require slightly

more force for optimum assembly.

The fourth requirement involves trying to concentrate the impact to the taper

junction and not down the stem where it could cause damage to the stem/femur

interface. It is also intended to ensure the efficient transfer of impact energy into the

junction and not to have it wasted through dissipation into the surrounding region.

4.2 Establishing and Defining User Needs

Since the fundamental design requirements had now been established, the next

step was to look beyond these fundamentals to establish other design requirements.

It is extremely important to involve the end user in the design of anything to ensure

that it meets their specific needs, so a survey was used to try to gather design

information that would help to ensure that the device would not miss out on any

important design features. After looking through several different methods of

gathering these requirements through a user-centred-approach [34], such as

ethnography or contextual inquiry, and consideration of the time and finance

available for this project, a survey directed at orthopaedic surgeons (the end users)

became the most suitable option.

The survey consisted of 8 questions, with a combination of both text response and

multiple-choice answers. The questions posed in this survey are now presented as

follows.

The beginning of the survey contained a very brief introduction into the background

of the survey and its aim. This is shown in Figure 9 as follows.

28

Figure 9: Orthopaedic Surgeon Survey Introduction

After the introduction to the survey, the first question posed attempted to gain an

understanding of the size of the range of different hip implants that were being used

and whether or not they were cemented or cement-less. This would influence

whether or not the device would be designed solely for use with a very popular

model. If a wide variance was uncovered, it would lead to designing a more flexible

device that could work with all different types of implants, or at least a large range of

them. The specific wording chosen for this question can be seen in Figure 10 as

follows.

Figure 10: Surgeon Survey, Q1

29

The next task was to establish the range of femoral head sizes. This was important

to establish so that the device could be designed to facilitate the most common

head sizes. This also fulfils the purpose of establishing a general impression of the

current use of large diameter (>36mm) MoM bearings, given their associated

problems previously mentioned in the literature review. The wording and layout of

this question is shown in Figure 11 below.

Figure 11: Surgeon Survey, Q2

Since it is important to understand the environment and orientation that the device

would be used in, the next question attempts to establish which surgical approaches

are used and which are the most common. The different approaches can determine

the patient’s position, i.e. lying face up, face down or on their side. This can have an

effect on the angle that the device may have to be used at, and impacts the

ergonomics of the design. This question is shown in figure 12 below.

30

Figure 12: Surgeon Survey, Q3

The next question aims to establish the size of the access area or incision in the

patient that the device must fit and function inside. The average size is 10cm, so this

question looks to see if many surgeons work under or above this incision size. This

question is shown in Figure 13 below.

Figure 13: Surgeon Survey, Q4

No instrumentation for the assembly has been discovered in previous investigations,

apart from the mallet and impactor. However, it is still worth raising the subject with

the surgeons, in case any custom-made or other such instrumentation is already

being used. This question is shown in Figure 14 as follows.

31

Figure 14: Surgeon Survey, Q5

The next question was not so much based on the establishment of design

requirements for the device, but more so at gathering data to compare with the four

studies listed at the end of the literature review. It was acknowledged that the

responses could not be looked upon too strongly, as the information provided by the

surgeons is opinion-based and thus is quite subjective. This question is shown in

Figure 15 below.

Figure 15: Surgeon Survey, Q6

An important opinion to gauge is the perceived importance of the isolation of the

impact to the taper junction so as not to damage the stem/femur interface. This

32

question was provided in a format where the participant rates the level of

importance out of 10. This question is shown in Figure 16 below.

Figure 16: Surgeon Survey, Q7

The   final   question   allowed   the   surgeon’s   to propose any features that they felt

should be included in the design of the device. The intention of this question was to

give the user an opportunity to directly propose things that were of importance to

them so that the design would have some sort of user-centred-design approach.

This question is shown in Figure 17 below.

Figure 17: Surgeon Survey, Q8

The survey was created and distributed among the members of the Royal British

Orthopaedics Association, following the completion of the Literature Review. The

survey received a very good response, as 109 surgeons participated. However,

survey participation only started towards the end of the project. Therefore the survey

responses could not be considered in the design of the device during this project.

33

However, a brief analysis of the survey has shown that there is a significant amount

of very relevant data available which would be of great value to the future

development of the device. A summary of the survey response is contained in

Appendix 1.

The original plan had been to gather the findings from the literature review and the

feedback from the survey and allow this to contribute to the PDS, but as mentioned

above this was not possible so for this reason none of the feedback from the survey

influenced the PDS. The PDS will now be discussed in more detail in the next

section.

4.3 Product Design Specification

The purpose of a PDS is to provide the designer with a list of design requirements

which can be regularly referred back to, so as to ensure that the design

requirements are being satisfied at each stage in the design process.  Stuart  Pugh’s  

“Total  Design  Approach”   had   a   significant   influence  of   the  way   in  which   the  PDS  

was generated for this project. Pugh’s  Product  Design Elements that made up the

Design core of his PDS document are shown in Figure 18 below. This provides a

good example of what sort of information goes into a full PDS.

34

Figure 18: Stuart  Pugh’s  Design Core [33]

Each and every Element’s constituent parts must have a measureable value so that

it can be clearly seen as to whether or not the design has satisfied the PDS.

However, given the time and detail involved in an industrial level PDS where such

detail is a requirement, this project used a slightly more simplified version. This

version which contains a listing of the different design attributes and considerations

that must be taken into account for the design to be successful in a clinical

environment. One of the first steps in generating requirements, and also in aiding

with concept generation in the later stages of the project, is to look into existing

designs and patent research. This allows the examination of features from

competitors or similar designs, and ensures that such a feature is not missed in the

design of this device.

35

4.3.2 Commercially available designs and patent research

As mentioned previously, the only commercially-available designs for the assembly

of the head/neck taper junctions are the orthopaedic hammer and impactor

methods. An in-depth patent search was carried out to establish what other like-

minded or similar and applicable designs already existed. Samples of some of the

more interesting designs are shown as follows. Some of these have made an

influence on the design of the device rig as can be seen later on in the Design and

Development stage.

Figure 19: Controlled Force Hammer [35] Figure 20: Controlled Force impacting device [36]

Figure 21: Handling Device for Hip Implant [37] Figure 22: Hip Joint Prosthesis and Fitting Tool [38]

36

Figure 23: Device for Handling Hip joint Heads [39] Figure 24: Head holder and impactor [40]

Figure 25: Method of applying Femoral head Resurfacing [41] Figure 26: Nail gun Patent 1 [42]

Figure 27: Nail gun Patent 2 [43] Figure 28: Wire Shelf Driver [44]

As can be seen from Figure 25 (resurfacing), and from Figure 26 to 27 (nail guns),

the patent search extended out to different devices with a similar purpose, which in

37

this case involved delivering an impact or maintaining an alignment. Rough notes

were taken during the patent search to keep track of any good ideas, which could

then be applied directly or manipulated to fit into the device proposed in this project.

Figure 29 and Figure 30, shown below; display two more applicable technologies

that could be of use for the concept generation stage later in the project.

Figure 29: Automatic Centre Punch [44]

Figure 30: Inserter jaw for knee prosthesis impaction and extraction [45]

38

4.3.1 Medical device standards review

Medical Device Classifications exist to grade the level of risk that a medical device

poses to a patient or user; the higher the grading, the more stringent the regulations

imposed on the development and manufacture of the device. There are different

classification systems for both the EU (EU/ISO [46]) and USA (FAA/ISO [47]), and

as the risk or grading increases, so too do the design regulations imposed by the

standardisation bodies to meet their audit requirements. The two grading streams

are illustrated side by side in an extract from medical Device Design by P.J.

Ogrodnik [48], as shown in Figure 31 below.

Figure 31: Comparison in grading between EU and USA Device Classification [48]

The device proposed in this project received the lowest grading in both systems

(grade I), meaning it has the lowest risk, as it does not remain inside the patient and

is in the same class as other common surgical tools, such as bone drill bits. This

means, as is indicated in Figure 31, that the device design is mainly self-regulated.

Several specific EU and US standards have been established that relate to the

device and are featured and referenced in the PDS, which is found in Appendix 1,

and is discussed in the next step. The purpose of the standard review was to

establish any significant design constraints that would affect the device. However,

as the device is only in an early prototyping stage in this project, it will not be ready

39

for clinical trials, so the standards review is of greater value further down the line in

future clinical design and development of this device.

4.3.2 Generation of PDS

The PDS pooled all of the design requirements acquired through the project so far,

and so took information from the Literature Review, the Surgeons’ Survey (although

left open, pending response from participants), the Standards Review, and the

patent and existing design research. The PDS is a working document, and can be

added to and edited as future work progresses on the development of the device

proposed in this project. The most up-to-date version of the PDS is included in

Appendix 2 [10].

40

5. DEVELOPMENT & EVALUATION

This chapter of the report looks at the generation, evaluation and development of a

concept for the device proposed in this project. It then examines the concept

generation, development, detailed design and manufacture of a proof-of-concept

Testing Rig, to verify the functionality of the overall device concept established in

the first phase.

5.1 Concept Generation and Evaluation

Since the PDS created in the previous chapter was quite detailed and in-depth, not

all of the points covered will be relevant at this stage in the design. It is for this

reason that the PDS was condensed down into its more critical attributes. This

created a less constrained environment to work in when generating creative

concepts. The new condensed PDS will be referred to as the “Initial PDS” from this

point on. Shown below is a summary of the steps taken in this concept generation

and evaluation phase.

Step 1: Creation of Initial Product Design Specification (PDS)

Step 2: Discretisation of design challenge

Step 3: Radial Thinking

Step 4: Visual Concept Analysis

Step 5: Critical Assessment and Selection

Step 6: Further Investigation of Powering Method

Step 7: Development of Final Powering Concept

Step 8: Mechanical Feasibility of Chosen Design

Step 9: Development of proof-of-concept Testing Rig

41

5.1.1 Initial Product Design Specification (PDS)

A full PDS was developed for a prototype device aimed at use in clinical trials but for

the purpose of this project, which will only be tested in laboratory conditions, the

original PDS was condensed down. This was carried out in order to focus on the

fundamental design requirements and to allow more creative freedom for concept

development. The PDS used for the project at this stage is shown below.

1. Performance 1.1 Must hold head taper axially aligned with neck taper axis

1.2 Must deliver impact axially aligned with neck taper axis

1.3 Must deliver adjustable impact from 4KN - 6KN to +/- 0.5KN

1.4 Must isolate impact to head-neck taper junction

2. Customer 2.1 Must be able to use with varying head size

2.2 Must be able to use with varying stem size

2.3 Must be able to position itself inside cavity created by incision

2.4 Easy to disassemble for cleaning and sterilization

3. User Friendly 3.1 Weight, preference to be lightweight

3.2 Easy to use, quick, low task complexity

4. Manufacture 4.1 Easy to Manufacture

5. Cost and Materials 5.1 Meet requirements above at minimum cost

5.2 Meet requirements above at minimum material use

Table 5: Initial PDS

42

An initial sketch was made at this point to record any design ideas that had come to

mind so far. This initial sketch is shown in Figure 32 as follows.

Figure 32: Initial sketch to capture ideas

5.1.2 Discretisation of Design Challenge

Even though the PDS was condensed down, the design challenge was still quite

complex. For simplification, this design challenge was split into four sub-systems so

that the concept generation could focus on the four key performance requirements

listed in the Initial PDS. These four key objectives are labelled with letters for clarity

during concept generation. The assignment of these letters is shown below.

(A). Hold head taper axially aligned with neck taper axis

(B). Hold impactor axially aligned with neck taper axis

(C). Deliver adjustable impact between 4KN and 6KN to +/- 0.5KN

(D). Isolate impact to head-neck taper junction

43

5.1.3 Radial Thinking

Radial thinking was used to expand on different concepts and help to develop and

record different concept ideas. Each of the four key objectives, A to D, were listed in

a bubble in the middle of a blank page and ideas stemmed outwards from this

starting point. Two examples of this exercise are shown as follows. Figures 33

shows the development of Objective B, and Figure 34 shows the development of

Objective C.

Figure 33: Development of Objective B

44

Figure 34: Development of Objective C

5.1.4 Visual Concept Analysis

After writing down all the different methods of achieving the objectives, the next step

was to roughly sketch them out so that they could be reasoned out visually and

analysed (keeping the Initial PDS in mind). For comparison to the method currently

used by the surgeons, a datum has been included at the beginning of each section

(where one exists). The rough sketches of the concepts are grouped within the four

key objective headings as follows.

(A). Holding head taper axially aligned with neck taper axis

*DATUM* Surgeon press fitting the head on the neck prior to impact

45

(A1). Three Prong Flexible Support and Centring Cone

Figure 35: Three Prong Flexible Support and Centring Cone Sketch

(A2). Semi-Cup + Centring Cone

Figure 36: Semi-Cup + Centring Cone Sketch

46

(B). Holding impactor axially aligned with neck taper axis

*DATUM* Surgeon holding impactor aligned by hand

(B1). Bent Hex-Rod

Figure 37: Bent Hex-Rod Sketch

(B2). Bent Rod Circular Profile

Figure 38: Bent Rod Circular Profile Sketch

47

(B3). Split Cup/Split Mould

Figure 39: Split Cup/Split Mould Sketch

(C). Deliver adjustable impact between 4.5KN and 11.5KN within +/- 0.5KN

*DATUM* Surgeon providing a hammer blow from a standard hammer

(C1). Slide Hammer - Direct Impact

Figure 40: Slide Hammer - Direct Impact Sketch

48

(C2). Slide Hammer - To Charge Spring

Figure 41: Slide Hammer - To Charge Spring Sketch

(C3). Magnets (forced together when opposing poles)

Figure 42: Magnets Sketch

49

(C4). Electro-Magnets (Solenoid Actuator)

Figure 43: Electro-Magnets Sketch

(C5). Screw Mechanism - No Impact

Figure 44: Screw Mechanism - No Impact Sketch

50

(C6). Screw Mechanism - To Charge Spring

Figure 45: Screw Mechanism - To Charge Spring Sketch

(C7). Lever - To Charge Spring

Figure 46: Lever - To Charge Spring Sketch

51

(C8). Pneumatic Piston

Figure 47: Pneumatic Piston Sketch

(D). Isolating impact to head-neck taper junction

*DATUM* Surgeons hand can grip the stem during impaction to prevent the impact

from being transferred to the patient

(D1). Rod Inserted In Stem Hole

Figure 48: Rod Inserted In Stem Hole Sketch

52

(D2). Mechanism to Hook around the Lips at Base

Figure 49: Mechanism to Hook around the Lips at Base Sketch

5.1.5 Critical Assessment and Selection

Each of the subsystems has been scored against their key design requirements and

the relevant Initial PDS requirements from 0 to 10, ascending in increments of two.

They are scored by how well they satisfy each of the requirements, as explained

below.

0 = “not  at  all”,

2 = “a  little”,

4 = “below  average”,

6 = “above  average”,

8 = “very  good”

10  is  “perfect”

53

The result of this exercise is the selection of concepts to address each of the four

key performance requirements. This exercise was carried out using an excel spread

sheet and is shown on the following page in Table 6. The highest scoring concept

from each of the four sections was highlighted in yellow.

54

Table 6: Scoring Table for Sub-System Concepts

55

As the outcome from Table 6 has shown, the following sub-system concepts have

been chosen and are listed as follows.

(A1) 3 Prong Flexible Support + Centring Cone

(B1) Bent Hex-Rod

(C8) Pneumatic Piston

(D1) Rod Inserted In Stem Hole

Since  the  main  function  of  the  device  is  key  requirement  C  (“Must deliver adjustable

impact from 4KN to 6KN, to +/- 0.5KN”) and the second and third ranked ideas in

this  category,  which  were  “Electro-Magnets”  (C4)  and  “Lever  to  charge  spring”  (C7),  

also scored relatively high, all of the top three designs in this category will be looked

into in more detail before finally settling on a single concept. It is also worth

mentioning that all combinations of selected successful concepts listed in the

paragraph above function collectively, and do not   work   against   each   other’s  

individual aims in the overall device design.

5.1.6 Further Investigation of Powering Concept

As mentioned previously, the top three design concepts to achieve Objective C are

as follows:

1. Pneumatic Piston

2. Electro Magnets

3. Lever to Charge Spring

Due to the importance and influence of correctly achieving objective C, each of the

top three designs were explored in more detail to ensure their engineering feasibly

56

in the design. This investigation was performed by looking into existing products that

were applying these three powering methods, and checking the suitability of each

method for the device in this project. These are examined as follows, starting with

the Pneumatic approach.

Pneumatic Piston

One of the best products to look at to examine the functionality of the different

methods of powering a device that provides an impact is the Nail Gun. A pneumatic

Nail Gun is shown in Figure 50 [49], below.

Figure 50: Pneumatic Nail Gun Illustration [49]

Figure 50 illustrates the basic process by which a pneumatic system works and it is

clear that it could be used in the device for this project. Pressurised air is provided in

the operating theatre up to 6 bar and pneumatic nail guns can run from 4 bar up to

22 bar for very heavy duty work. It is a clean and sterile method of operation.

However, it would reduce the simplicity of the design as the use of pressurised air

57

can become quite complex and expensive when designing and manufacturing. This

project is trying to provide the simplest possible powering method, so for this reason

the pneumatic approach does not seem to be the best fit.

Electro magnets

Electro magnets, or specifically in this case electro solenoids, can be used to

electrically initiate magnetic fields, which can propel objects to create an impact.

This type of system is explained once again using a nail gun example in Figure 51

[49] below.

Figure 51: The Solenoid Powered Nail Gun [49]

Again, it is clear that this sort of technology could be used to power the device for

this project. Electricity is available in the operating room to power other electric

medical devices, and battery packs can also be used to power such a system.

However, the use of electro solenoids means that there will be electromagnetic

fields generated which can interfere with other medical devices and patient implants

58

that may be close to the device when in use. This also, much like the pneumatic

option, this greatly increases the complexity in the design and means that the device

will have to abide by more constraining standards during the design process. This

will add difficulty and complexity to the future work on a clinical device, and thus

rules out this technology as a possible option.

Lever to Charge Spring

The final option for powering the device is a charged spring, which is compressed

using mechanical advantage, such as a lever system. An electrically powered

mechanical spring system is shown in Figure 52 below, again using an example of

an electric powered nail gun.

Figure 52: Electric Powered Nail Gun [49]

This sort of powering method would be the simplest to design, and could be

adjusted to remove the need for an electric power system. By using a pure

mechanical system, it would simplify the design even more and make the device

59

more sustainable and reliable with no dependency on other inputs such as electricity

and compressed air. The surgeon could use their energy to provide the work

required to compress/charge the spring could be made easier with a leverage

system. An example of the employment of this sort of powering mechanism is

demonstrated in a simple can-crushing device as shown in Figure 53 below.

Figure 53: Can-Crushing Device [50]

Final Selection of Powering Method

After reviewing the different strengths and weaknesses of employing each of the

three different powering methods, as discussed previously, the option that seemed

the most appropriate to this design was the spring compressed/charged by a

mechanical advantage or levering system. This concept was then developed further

in the next step of this process.

60

5.1.7 Development of Final Powering Concept

Now that the method which would power the device had been chosen, the next step

was to develop the design in more detail to prove that it could actually work.

There were three main design objectives that had to be met for the device to be able

to function. The first was to confirm the final leverage method to compress the

spring. The second was to come up with a way in which the device could deliver an

adjustable impact (which had not been focussed on previously). Finally, the third

objective was to design a trigger/release mechanism to actuate or initiate the

impact.

Mechanical Leverage System

This stage involved more sketching and research, but this time just focussed on

leveraging systems. Items such as hand-operated juicers, in which they compress

the fruit to extract juice, were seen as applicable to the design of the device. A

rough sketch showing the integration of such a system into the spring compression

system is shown in Figure 54 below.

Figure 54: Adapted Juicer Sketch

61

More can-crusher products were also investigated, and an example of one of the

sketches trying to use this approach is shown in Figure 55 below.

Figure 55: Adapted Can Crusher Sketch

These designs all seemed as though they would need quite a long handle to

produce an adequate amount of enough force to compress a spring stiff enough to

provide the impact energy needed for the device. One way of shortening the

handles was to use two handles simultaneously. This is the sort of leverage system

that is used on a typical wine bottle corkscrew. A sketch utilising the application of

this design in the concept for this device is shown in Figure 56 as follows.

62

Figure 56: Corkscrew Lever System Sketch

This sort of mechanism could be attached onto the end of the device, and the

surgeon could use both hands to push the levers down to the sides of the device.

This would compress a spring that can be held in place by a locking mechanism and

released by a trigger when ready for use.

Adjustability

The spring would need to be adjustable to between 4KN and 6KN as mentioned

previously, and so a mechanism would need to be designed to allow such flexibility

over   the   device’s   output. Several spring adjustment designs are shown in the

Figures 57, 58 and 59 as follows.

63

Figure 57: Twisting Adjustment and Release Concept Sketch

Figure 58: Gearbox Style Spring Compression Adjustment Concept Sketch

64

Figure 59: Spring Compression adjustment System Sketch

Trigger/Release Mechanism

A trigger/release mechanism would also be required so that the spring could be

compressed away from the patient, locked in the compressed position, and then

brought to the patient for use so that it could be discharged when the surgeon had

the device in place. Several trigger mechanism concepts are presented in Figure 60,

61 and 62 as follows.

65

Figure 60: Slotted Trigger Release Mechanism Sketch

Figure 61: Firearm Trigger Concept Sketch

Figure 62: Handle Trigger System Sketch

66

Selection of the Concept for Objective C

The final selection of the concept for the device is shown in Figure 63 below. This

incorporates the corkscrew method of leverage seen in Figure 56 previously,

positioned out of sight to the left of the lower sketch within Figure 63 below. It also

incorporates an adjustable force mechanism behind the spring and a trigger

mechanism as shown.

Figure 63: Final Developed Concept Sketch

To give an indication of the three dimensional shape of the device, Figure 64 as

follows, illustrates a conceptual representation of the tubular casing which surrounds

the spring.

67

Figure 64: Tubular Casing Surrounding Spring Sketch

5.1.8 Mechanical Feasibility of Chosen Concept

Before progressing further, the leverage mechanism must be validated theoretically

to ensure that it could realistically function and be used by a surgeon. A rough

sketch of the device moving through the charging motion is shown in Figure 65

below from left to right.

Figure 65: 3 step sketch illustration of corkscrew charging method

68

The leverage force has been simplified and marked out on the Figure 56 which is

shown again below and renamed Figure 66 for clarity.

Figure 66: Force Balancing Free Body Diagram

Analysing the diagram in its static state, it can be assumed that all forces acting on

the spring and lever are balanced, as it is not in motion and the spring is loaded in

compression. L1 is the distance from the centre of the gear wheel to the point at

which the gear teeth mesh on the ridged shaft. L2 is the distance from the centre of

the cog wheel to the end of the handle. F1 (take as 6KN) is the spring force acting at

this point in the direction of impact. F2 is the resultant force of the spring acting on

the handle.

Taking L2 as 0.3m (300mm) and L1 as 0.01m (10mm) for a trial basis, F2 can be

found and it can be established whether or not it is humanly possible to compress

and hence charge the device.

69

Using static force balancing analysis, Equation 1 can be derived and is as shown

below.

𝑭𝟐 = 𝑭𝟏×𝑳𝟏𝑳𝟐 (1)

Substituting in the values;

𝐹2 = (6 × 10 ) × 0.010.3

Solving for F2;

𝐹2 = 200𝑁

Since there are two levers used on the device this force can be divided by 2, so;

𝐹2 = 100𝑁

To put this in terms that are easy to comprehend, the answer is put in terms of a

weight hanging in the opposing direction to F2 (as seen in Figure 66). The weight

can be found using Equation 2 shown as follows;

𝑭 = 𝒎𝒈 (2)

Where;

g = acceleration due to gravity (constant = 9.81m/s2)

70

Substitute in known values;

100 = 𝑚(9.81)

Rearrange and solve for m;

𝑚 = 10.2𝐾𝑔

Where;

Kg = Kilogram

This means that a 10.2Kg weight could be hung on one side, and it can be

visualised that the same force could be mirrored onto the other handle to statically

hold the whole device in place. Since this is has been sized for 6KN, it is the

toughest possible scenario. This is thus deemed an acceptable method as the

handles can be made longer and other design attributes can be manipulated to

reduce this value. So far, the mechanism has proven itself enough at this stage of

the design to continue in the process.

The next step was to size a spring capable of providing an impact magnitude of up

to 6KN. Using the impact impulse equation (Equation 3) below;

𝑰𝒎𝒑𝒖𝒍𝒔𝒆 = 𝑭. ∆𝒕 = 𝒎. ∆𝒗 (3)

71

Where;

F = Impact Force

Δt = Impact duration (time over which impact occurs)

m = Mass

Δv = change in velocity

The force used in this equation is 6KN, since it is the highest end of the scale.

The mass used for this calculation was based on the average mass of an

orthopaedic mallet, which was found to be approx. 0.4Kg (kilograms).

Since the impact duration is unknown, a previously-recorded impulse value was

taken from a PhD student at the University of Bath who had carried out a study on

impacts and had acquired this data for 2KN, 4KN and 6KN impact forces. It should

be noted that the tip material used during these tests is unknown, and this may have

a large effect on the testing results. The impulse recorded for 6KN was 11.1Ns

(newtons per second).

The change in velocity (Δv) is equal to the initial velocity (u) minus the final velocity

(v), i.e. Δv = u – v. The final velocity is zero since the mass comes to a complete

stop. These new values can be subbed into Equation 3 as follows.

11.1 = 0.4(𝑈 − 0)

Rearranging and solving for U;

𝑈 = 27.75  𝑚/𝑠 Where

m/s = metres per second

72

Now that the initial velocity has been found, this can then be used to find the kinetic

energy (KE) at the point of impact. This can be found using Equation 4.

𝑲𝑬 = 𝟏𝟐𝒎𝒗𝟐 (4)

Substituting in the known values;

𝐾𝐸 = 12 (0.4)(27.75)

Solving for KE;

𝐾𝐸 = 154.0125  𝐽𝑜𝑢𝑙𝑒𝑠

If it is assumed that there are no losses, and the KE at the point of impact is equal to

the Potential Energy (PE) stored in the spring after it has been compressed but

before it has been released, then the KE found in the previous step can be used as

the PE in Equation 5 as follows.

𝑷𝑬 = 𝟏𝟐𝒌𝒙

𝟐 (5)

Where

k = spring stiffness

x = spring displacement

73

Since both k and x are both unknown at this point, it is decided to use a spring

displacement (x) of 60mm (millimetres) or 0.06m (meters). This has been chosen as

this displacement should leave enough room for sensitive adjustments to be made

to the spring later in the design process.

Substituting these values into Equation 5;

154.0125 = 12𝑘(0.06)

Rearranging and solving for k;

𝑘 = 85562.5𝑁/𝑚

Where

N/m = Newton per metre

Using this k value as a guide, a spring could then be sized from a components

catalogue. The spring had to have a minimum k value of 85562.5 N/m but also had

to have a compression displacement range of roughly 60mm to ensure the

adjustability of the spring for different impact force magnitudes.

5.1.9 Development of Proof-Of-Concept Testing Rig

Before any further development could continue on the concept developed at this

point in the project, the basic idea of using a spring to deliver the assembly impacts

74

had to be proven experimentally first. This was to be proven using a testing rig

designed purely for this purpose.

The first step in this process was to size a spring. The k value found in the last

section and the displacement of approx. 60mm was used to source a spring from

Lee Springs. The specifications for this spring are shown in Appendix 3.

It was also decided to use three magnitudes of impact force during testing. This was

done so that a line could be graphed through the three averaged points on an

impact impulse vs. spring compression displacement chart to show the predictability

and repeatability of the spring method. It could also be used as an opportunity to

explore the effects of different tip material on the impactor, and what effect they

have on the process.

To simplify the design, an Instron Impact Loading machine (30KN max load), as

shown in Figure 67 below, would be used to compress the spring to the required

compression displacements. This would make the design stage simpler and faster

to design and manufacture.

Figure 67: Instron Loading Machine [51]

75

The key functions of the testing rig were to allow the Instron to compress the spring,

to hold the spring in its compressed state and then to allow the spring to be

released over a load cell in order to measure the impact force administered.

One of the early sketches in the concept development stage for this rig is shown in

Figure 68 below.

Figure 68: Initial Testing Rig

76

Figure 68 includes a lever release mechanism, which is actuated by twisting a collar

fixed on the outside of the top cylinder (illustrated in the top left of the Figure). It also

features a threaded shaft with a threaded stopper disc that can be adjusted to allow

varied spring compression displacements. The design was refined further to try to

reduce its complexity, so as to save time during the detailed design phase and

manufacture. Figure 69, below, shows the refined version of the concept for the

testing rig.

Figure 69: Simplified Concept for Testing Rig

77

The device could be removed from a solid plate base on which a load cell would be

secured, and then mounted using a special jig. This would be done so as to allow

the Instron to push down the body of the device with the impactor tip placed on a

fixed spigot so that the spring could be compressed inside.

Various trigger mechanisms were generated, with the final idea being a side-acting

lever. This lever would then fit into one of three specifically laid out slots that were

designed to allow the spring to be held in a compressed state under 6KN, 4KN and

just over 2KN of load in the Instron. Figure 70 below, shows the first concept,

followed by Figure 71, which shows the next development, and then finally Figure

72 showing the simplified lever release mechanism.

Figure 70: Initial Lever Design

78

Figure 71: Lever Design Development

Figure 72: Final Lever Design

79

5.2 Detailed Design

The Test Rig concept could now be developed further on SolidEdge. Stress

calculations and considerations could also be made for the manufacture of the

device, and could be followed by, the provision of draft drawings to the Machine

Shop and the manufacture of the testing rig.

5.2.1 Solid Modelling

The design had three specific compression displacement slots, slotted into an

internal impactor rod (visible in Figure 73 below protruding from the top of the

device), which was propelled by the release of the compressed spring. An isometric

view of the finished model is shown in Figure 73 below, with fasteners removed for

clarity. The assembled model is shown at the 6KN load setting.

Figure 73: Final Assembled SolidEdge 3D Model

80

5.2.3 Draft Drawings

Once the final solid models had been completed a full set of draft drawings were

produced for the design. These drawing are listed in Appendix 4 and can also be

found towards the end of the report.

5.2.4 Manufacturing

The SolidEdge solid modelling program allowed the interaction between the parts to

become visible, and the manufacturing methods could be taken into consideration.

The Testing Rig was manufactured in a machine shop based in the University of

Bath and so the development of the design on SolidEdge was reviewed in stages

with the Machine Shop Technician that would be manufacturing the Rig. This helped

to simplify the manufacturing stage, as the design was customised to make use of

the most easily-available materials that were currently in stock. The device was

manufactured from steel, with exception of the bushings, which were made from

PVC, and the interchangeable material tips which were made of PVC, Mild Steel,

Nylon and Rubber.

81

6. TESTING

This section of the report covers the calibration of the load cell and the testing

carried out on the Rig. The Results from this testing will be discussed in the next

Chapter.

6.1 Calibration of the Load Cell

The first step was to calibrate the Load Cell, which would be used to measure the

impact loading during the Rig testing. This was performed to ensure that the load

cell was fully functional, and also to establish a scale factor so that the output, when

Rig testing, could be provided in newton instead of in volts, which is what the load

cell measures.

An Instron loading machine (max loading of 30KN) was programmed to descend

onto the Load-Cell in steps of 2KN up to 8KN. The Load-Cell was attached to

computer through an Analogue to Digital Card which was linked to a load

measurement program designed for use on LabView. This allowed the load cell

voltage recordings, which were being recorded at a sample rate of 10,000 samples

per second, to be written and stored in a text-file on the hard drive of this computer.

The loading test was performed three times to gain an average value across the

tests for each load, which would allow for any errors or outliers. After the testing was

completed text-files were then imported into Matlab and the voltage was plotted

against time. Figure 74 as follows, shows the graph for the first test.

82

Figure 74: First Calibration Test plot of Voltage Vs. Time

It is clear from Figure 74 that the line sloping downward from right to left has four

small steps, which represent 2KN, 4KN, 6KN and 8KN Loads. These loads are

represented on the graph in volts. The voltage at each of these steps was recorded

and inserted into a spread sheet on excel. Table 7 below shows the data recorded

from the three tests and shows the average voltage achieved at each load.

Table 7: Data recorded during Load Cell Calibration

83

This Data was then plotted and a trend line added across the average points so that

the slope, and hence the scale factor, could be established. This chart is shown in

Figure 75 below.

Figure 75: Load Cell Calibration Test Data Plotted on Graph

The close proximity of the trend line to the points on Figure 75 showed that the load

cell was fully functional and the change in voltage for each load was proportional. It

is clear to see from Figure 75 above that the scale factor is -2678.5. This scale

factor was then programmed into LabView prior to testing so that the text-file

readings were produced in newtons as opposed to volts.

6.2 Rig Testing

After the Load Cell was calibrated, verified as fully functional and the scale factor

was established, the Rig Testing could begin.

y = -2678.5x + 13.413

0100020003000400050006000700080009000

-4.0000 -3.0000 -2.0000 -1.0000 0.0000

Load Vs. Voltage

Load Vs. VoltageLinear (Load Vs. Voltage)

84

6.2.1 Procedure

The testing involved measuring and recording several variables. These variables

are listed as follows.

1. Final displacement of spring during spring compression on Instron

2. Final load recorded during spring compression on Instron

3. Impact data recorded via LabView

Variable 1 and 2 were read directly from the computer monitor hooked up to the

Instron. The LabView data was analysed later using Matlab.

The Testing procedure involved several steps. The first step involved slotting the

required material tip into the hole at the tip of the impactor rod and then holding it in

place with the grub screw. The next step was to mount the Spring Section of the

Testing Rig onto the test fixtures, which had been designed and manufactured as a

part of this project. They held the rig in a safe and secure position during the

compression of the spring on the Instron. Figure 76 below shows the two fixtures

mounted on the top and bottom of the Instron attachment points.

Figure 76: Custom Mounting points, close up view of top, close up view of bottom

85

Figure 77, as follows, shows the Spring Section of the Device fixed securely in the

mounting points.

Figure 77: Spring Section in mounting points, close up view of top, close up view of bottom ger

The top fixture was then lowered to the point where the device was securely in

position. The spring section was then compressed in very small increments until

spring compression was recognised visually by watching the top of the impactor rod

rising up out of the casing. Once this point was reached the Instron displacement

and load measurements were set to zero and the spring was slowly compressed

until the release lever could fit all the way into the assigned slot in the impactor rod

(for that particular test). Once the lever had been moved into place in the slot, the

displacement and load were then recorded on an excel spread sheet.

The next step was to raise the top fixture to its original position, insert the safety pin

which held the release lever in place, remove the spring section which was then

mounted onto the base plate which has the load cell fixed to it with two bolts. The

first round of material testing at just over 2KN was carried out without a rubber base

between the base plate and the table, to which the base plate was held in place with

86

g-clamps. Figure 78, as follows, shows the base plate mounted to the table with and

without the rubber base and finally with the spring section sitting top of the base

structure prior to the assembly nuts being screwed attached.

Figure 78: Base plate fixed to table with and without Rubber Base

The Spring Section of the Device was then fixed in place with nuts above and below

its lower flange (eight nuts below, and four above the flange, in total). The LabView

program was then initialised, the offset reset (for each test) and the sampling

started. The safety pin was then removed from the lever and a copper faced mallet

was used to aid the quick release of the lever by impacting the end of the release

lever to  ensure  a  swift  removal  of  the  lever  from  the  impactor  rod’s  path.

This procedure was repeated for each individual impact test. To provide a

walkthrough of one such test a 3 minute video of one impact test was recorded with

a walkthrough narrative and posted to a DropBox online account. This video can be

87

accessed by copying the following file link into the address bar on an internet

browser.

https://www.dropbox.com/s/6o668aoik0xtirz/video-2013-08-21-12-46-46.mp4

6.2.2 Data recorded

The materials were changed over after each test. The material testing order was

steel, nylon, PVC rubber and then back to steel again, which started off the next

round of testing. This allowed the rubber time to return to its original shape and

elasticity, as it temporarily deformed following impaction.

Figure 79, as follows, displays the displacement and load data which was recorded

during the Rig testing on an excel spread sheet. This figure also contains notes that

were taken to record changes in material tip samples following the failure of a

material tip during a test.

88

Figure 79: Table of Data recorded from Instron

89

The impact data recorded using LabView was extracted from the text file output

using Matlab and then inserted into an excel spread sheet for analysis. The

parameters analysed for each impact test were as follows.

1. Peak Force recorded during impact in Newtons

2. Duration of Max Peak in Seconds

3. Duration of impact

These were extracted from graphs generated on Matlab and then fed into the excel

spread sheet. Figure 80, below illustrates the 3 parameters recorded from these

graphs.

Figure 80: Test 2, Steel, 2KN (with rubber base)

The extrapolated load cell data for the 2KN loads are shown in Figure 81 as follows.

Only one round of data was taken without the rubber base present, to see effects of

90

vibration damping. The rubber can be considered as a representation of the soft

tissue in a patient as it absorbs some of the impact force from the Testing Rig.

However, it must be noted that an error occurred and the steel test wrote over the

Nylon test, hence why they both have the same data in the single round of testing

without the rubber base. The analysis of this data is covered in the next section of

the report.

Figure 81: Extrapolated Load Cell Data, >2KN

The impulse data was calculated by multiplying the “Peak Force” by the “Duration of

Impact”, using Equation 3 as stated previously in the report.

91

Figure 82: Extrapolated Load Cell Data, 4KN and 6KN

The extrapolated load cell data for the 4KN and 6KN loads are shown in Figure 82

as follows.

92

7. RESULTS AND DISCUSSION

This section of the report covers the analysis and discussion of the Instron and Test

Rig Data acquired in the previous chapter and also an evaluation of the Testing Rig.

7.1 Evaluation of Instron Data

During the testing phase, some notes were made on the spread sheet where the

Instron data was being recorded. For example, as can be noted from the comments

on Figure 79 shown previously, both PVC and Rubber failed on the first round of

testing at 4KN of loading on the Instron. New replacement tips for both materials

failed after Round 2 (their first impacts) at 4KN loading. Figure 83 below shows

images of the PVC and Rubber Tip materials which were destroyed on Round 1 of

the 4KN Testing.

Figure 83: Images of Failed PVC and Rubber Tips at 4KN Load

93

It  was  also  clear  from  the  “average  max  displacement”  figures  shown  previously   in  

Figure 79 that the Rubber Tip Sample compressed during loading on the Instron to

approx. two thirds of its original thickness. This pre-deformation may have reduced

the ability of the material to lower the impulse force (as it would normally prolong the

impact duration of the peak force as seen from the load cell data).

There was some error present in the inconsistency at the point at which the load

and the displacement were reset to zero on the Instron before the spring was

compressed. There was a learning curve during the experimentation and it was

discovered towards the end of the testing that the best time to reset the load and

displacement readings to zero, before compressing the spring, was to watch to see

the top of the Impactor rod move in relation to the devices outer structure. This way

it was sure to be the point at which the spring was about to experience actual

compression, as opposed to the rig just settling out. However, even taking this error

into account the average max displacements during loading for the four materials

agree with the resistance of the materials to compression during loading. Steel

resisted compression the best, followed by Nylon and PVC in joint second and then

followed by rubber last (as confirmed by the load cell data).

7.2 Evaluation of Load Cell Data

The loads experienced during the test were of a far greater magnitude than

expected. This error can be traced back to the use of the Impulse value taken from

the PhD student’s  previous  study.  It  is  now  clear  from  the  values  provided  in  Figures  

81 and 82 that the impulse force reduces significantly on the 2KN loading tests (with

rubber base) from 5142.5 Ns for steel, to 4556.18 Ns for Nylon, to 3479.28 Ns for

PVC, down as low as 692.14 Ns for Rubber. This shows that the tip material had an

94

extremely large effect on the duration of the max peak which in turn affects the

resulting calculation of the impulse force. It is important to note that when using

these original impulse values the tip material used in the study in which the impulses

were recorded, was not provided to this project. This would explain to some degree

the significantly high impact forces recorded, especially with steel, which in many

cases exceeded the measurement band of the Load Cell. As per the specifications

on the Load Cell it has a max measurement capacity of 5,000 lbs (or 2267.69 Kg, or

22,246 N). The Load Cell can only measure up to 10 Volts which works out as

approximately 26,785 N, when referring back to the scale factor. It is clear that the

bandwidth of the Load Cell could not cope with the large magnitudes of force being

delivered. This brings into question the remaining results as the forces being

recorded were far greater than what was to be expected. When the Steel testing

was performed for the 6KN loading it was deemed that the load cell had been

damaged as the load reading following the impact was set permanently on approx.

25KN. Further analysis of the cables attaching the load cell to the computer was

carried out using a dummy transducer and no problems were found. However, when

testing the resistance across a wheat-stone bridge linked into the load cell an

imbalance was recorded. This indicated that at least one of the strain gauges has

been damaged and so the testing could not be continued.

Another important factor related to the experimental impulse values sourced for this

report was that that value was achieved through monitoring the assembly of a head

on a neck taper and so this would have a displacement as the head moved down

the neck taper, as it was driven by an impact. The load cell would have a much

smaller increment by which it would deflect and hence would increase the impulse

force as the peak force would spike extremely high (as can been seen from the load

95

cell data) due to the extremely sudden momentum change, as it bounces off the

load cell.

7.3 Evaluation of Testing Rig

Despite the greater peak forces than expected, the Testing Rig performed extremely

well given that the load cell failed before the Testing Rig. It functioned safely under

the loads and was quick and simple to use. The only improvements for future use

would be shortening the four threaded studs holding the spring section to the base

plate as this could be a little time consuming screwing the nuts on and off the long

sections when assembling and disassembling the rig during tests. The edge of the

release lever that fitted into the slots came under great deal of stress and future

designs may benefit from heat treating to harden the edge to reduce wear when

removing the lever under load.

7.4 Discussion

To improve the testing in the future, a hip model where the head/neck displacement

and impulse force during impaction is known, and tip material and size used should

be known prior to spring sizing calculation. A single tip of nylon should suffice for the

testing as the Nylon survived much higher impulses in the experiment in this project.

Instead of a bolt screwed into the load cell, the same hip model as mentioned above

should have its stem cut down to size so the base of the neck taper can be attached

directly to the load cell. The head/neck assembly can them be pulled apart using

pull-off and twist-off tests and compared against control specimens that have been

assembled using a mallet and impactor.

96

8. CONCLUSIONS

This section looks at the overall outcome from the different sections of this project

and their contribution to the overall aim of designing and developing a medical

device to improve the assembly of head/neck taper junctions in MTHRs.

To start with, a significant literature review was carried out for this project which

resulted in the definition of fundamental design requirements for the proposed

device. These requirements were based on an analysis of the most relevant and

credible sources available.

The user needs and design requirements developed in the next stage of the project

were of significant value, particularly the Surgeons Survey and the PDS. The

Surgeons Survey, although the feedback came late in the projects life it is still of

great value to this project and other studies in the region of MTHR taper junction

analysis. The Surgeons Survey gathered relevant information from over one

hundred specialists in the field of Orthopaedics. There is considerable future work in

analysing the data provided in this feedback, but it may hold significant findings to

help further understand the problem at hand and aid in the development of the

device developed in this project. The PDS contains a wealth of design attributes,

considerations and standards for which future generations of the device design will

come to find more relevant as the design develops. It has also helped add clarity to

the feasibility of producing such a device, in so much as medical device

classification and the applicability of certain standards.

The generation and selection of a concept for the final working device not only aids

the future development of the device but again also proves the feasibility of the

device. The final concept shows that a collection of simple mechanisms can easily

satisfy the design requirements established earlier in the project.

97

The development and manufacture of the Testing Rig has produced a finished

device which can be reused for future testing or can be manufactured again on a

smaller scale to suit a smaller spring size. All of the manufacturing draft drawings

are contained in the Appendix and only need to have the dimensions scaled down

and another smaller version could easily be produced.

The data acquired from the testing phase has shown the dramatic influence that the

tip material has on the impulse force. It has also uncovered improvements for future

testing, such as impacting a head/neck assembly fixed to a load cell and using a

smaller spring size, followed by comparing the assembly and disassembly data with

specimens assembled using a mallet and impactor.

Overall, this project has produced a detailed final design concept which can meet

the design requirements established in this project. It has also produced a testing rig

capable of aiding the laboratory development of this design concept. The feasibility

and benefit of developing the design concept has been proven in every stage of the

project

A significant amount of future work is still required to bring the proposed device to

market. It is clear from every stage of this project, that by continuing the

development of this device, it can contribute to the reduction in early revision

surgeries on MTHRs.

98

10. REFERENCES

1. Wiesel, S.M.a.D., J.N., Essentials of Orthopedic Surgery. Third ed. 2007, LLC, 233 Spring Street, New York, NY 10013, USA: Springer Science+Business Media.

2. Pnnimadu. Hip Replacement Surgery. 2011 [cited 2013 August]; Available from:

http://www.zimbio.com/Hip+Implants/articles/mD7tOajiDxw/Hip+Replacement+Surgery.

3. Charnley, J., Surgery of the hip-joint: present and future developments. Br Med J,

1960. 1(5176): p. 821-6. 4. Delaunay, C. The Charnley Total Hip Replacement - The Gold Standard of primary

hip replacement, 36 years on. 1998 [cited 2013 May]; Available from: http://www.maitrise-orthop.com/corpusmaitri/orthopaedic/mo83_delaunay/delaunay_us.shtml.

5. UK, S. Hip Replacements. 2013 [cited 2013 August]; Available from:

http://www.stryker.co.uk/index/st_pag_patients-home/st_pag_patients-hip/st_pag_patients-hip-replacement.htm.

6. McCarthy, J.C., J.V. Bono, and P.J. O'Donnell, Custom and modular components in

primary total hip replacement. Clin Orthop Relat Res, 1997(344): p. 162-71. 7. Smith, E. Mr. Everet Smith, Innovations in Total Hip Replacement. 2008 [cited 2013

May]. 8. Loch, D.A., Gleason, R.F., Kyle, J.E., Bechtol, D., Axial pull-off strength of dry and

wet taper head connections on a modular shoulder prosthesis. Presented at Orthopaedic Research Society, 1994. 19: p. 826.

9. Schramm, M., et al., The Morse taper junction in modular revision hip replacement--

a biomechanical and retrieval analysis. Biomed Tech (Berl), 2000. 45(4): p. 105-9. 10. Maguire, R., Literature Review: Design and Development of a Medical Device to

Improve the assembly of Head/Neck Taper Junctions in Modular Total Hip Replacements, in Department of Mechanical Engineering. 2013, University of Bath.

11. Haddad, F.S. Fares Haddad, Consultant Orthopaedic Surgeon. 2006 [cited 2013

May]; Available from: http://www.fareshaddad.co.uk/hipimages.html. 12. g-Source. Orthopedic Surgeons Catalog. 2013 [cited 2013 August]. 13. Langton, D.J., et al., Accelerating failure of the ASR total hip replacement. The

Journal of Bone & Joint Surgery, 2011. 93-B(No.8). 14. Heneghan, C., D. Langton, and M. Thompson, Ongoing problems with metal-on-

metal hip implants. BMJ, 2012. 344: p. e1349. 15. Smith, A.J., et al., Failure rates of stemmed metal-on-metal hip replacements:

analysis of data from the National Joint Registry of England and Wales. The Lancet, 2012. 379(9822): p. 1199-1204.

99

16. Medical Device Alert: MDA/2012/036 - All metal-on-metal (MoM) hip replacements, MHRA, Editor. 2012: United Kingdom.

17. Bishop, N.E., F. Waldow, and M.M. Morlock, Friction moments of large metal-on-

metal hip joint bearings and other modern designs. Med Eng Phys, 2008. 30(8): p. 1057-64.

18. Langton, D.J., et al., Taper junction failure in large-diameter metal-on-metal

bearings. Bone Joint Res, 2012. 1(4): p. 56-63. 19. Goldberg, J.R., et al., A multicenter retrieval study of the taper interfaces of modular

hip prostheses. Clin Orthop Relat Res, 2002(401): p. 149-61. 20. LLP, P.S. Mismatched Hip Replacement Components. 2012 [cited 2013 August];

Available from: http://www.pryers-solicitors.co.uk/blog/clinical-negligence-news/mismatched-hip-replacement-components/.

21. Fessler, H. and D.C. Fricker, A study of stresses in alumina universal heads of femoral prostheses. ARCHIVE: Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 1989-1996 (vols 203-210), 1989. 203(18): p. 15-34.

22. Shareef, N. and D. Levine, Effect of manufacturing tolerances on the micromotion at

the Morse taper interface in modular hip implants using the finite element technique. Biomaterials, 1996. 17(6): p. 623-30.

23. Lieberman, J.R., et al., An analysis of the head-neck taper interface in retrieved hip

prostheses. Clin Orthop Relat Res, 1994(300): p. 162-7. 24. Bobyn, J.D., et al., Concerns with modularity in total hip arthroplasty. Clin Orthop

Relat Res, 1994(298): p. 27-36. 25. Goldberg, J.R. and J.L. Gilbert, In vitro corrosion testing of modular hip tapers. J

Biomed Mater Res B Appl Biomater, 2003. 64(2): p. 78-93. 26. Mroczkowski, M.L., et al., Effect of impact assembly on the fretting corrosion of

modular hip tapers. J Orthop Res, 2006. 24(2): p. 271-9. 27. Callaway, G.H., et al., Fracture of the femoral head after ceramic-on-polyethylene

total hip arthroplasty. J Arthroplasty, 1995. 10(6): p. 855-9. 28. Pansard, E., et al., Severe corrosion after malpositioning of a metallic head over the

Morse taper of a cementless hip arthroplasty. A case report. Orthop Traumatol Surg Res, 2012. 98(2): p. 247-50.

29. Pennock, A.T., A.H. Schmidt, and C.A. Bourgeault, Morse-type tapers: factors that

may influence taper strength during total hip arthroplasty. J Arthroplasty, 2002. 17(6): p. 773-8.

30. Lavernia, C.J., et al., The effects of blood and fat on Morse taper disassembly

forces. Am J Orthop (Belle Mead NJ), 2009. 38(4): p. 187-90. 31. Heiney, J.P., et al., Impact magnitudes applied by surgeons and their importance

when applying the femoral head onto the Morse taper for total hip arthroplasty. Arch Orthop Trauma Surg, 2009. 129(6): p. 793-6.

100

32. Rehmer, A., N.E. Bishop, and M.M. Morlock, Influence of assembly procedure and material combination on the strength of the taper connection at the head-neck junction of modular hip endoprostheses. Clin Biomech (Bristol, Avon), 2012. 27(1): p. 77-83.

33. S, P., Total Design: Integrated methods for successful product engineering. 1991:

Addison-Wesley Publishing Company Inc. 34. Martin, J.L., et al., Capturing user requirements in medical device development: the

role of ergonomics. Physiol Meas, 2006. 27(8): p. R49-62. 35. Controlled Force Mallet. 24/12/1992. 36. Controlled Force Impacting Device. 31/03/2006. 37. Handling Device for hip Prosthesis implant. 2/3/1988. 38. Hip Joint Prosthesis and Fitting Tool. 24/10/1997. 39. Device for handling ball heads of joint prostheses. 2003. 40. Femoral Head Holder and Impaction Instrument and Method of use. 2003. 41. Method of applying a femoral head resurfacing prosthesis. 2007. 42. Geraet zum Eindruecken von Heftzwecken. 1952. 43. Hand-held nail gun has helical driving spring made of tubular spring steel. 2007. 44. Wire shelf driver. 1999. 45. Claypool, J.L., Krebs, J. Inserter jaw for a prosthesis impaction and extraction tool.

2013; Available from: http://www.strutpatent.com/patent/d0651310/inserter-jaw-for-a-prosthesis-impaction-and-extraction-tool#!prettyPhoto.

46. Communities, T.C.o.T.E., Council Directive 93/42/EEC. 1993. 47. FDA, 21 CFR Part 860 – Medical Device Classification Procedures. 2010. 48. Ogrodnik, P.J., Medical Device Design: Innovation from concept to market. 2013:

Academic Press. 49. Harris, T. How Nail Guns Work. 2001 [cited 2013 August]; Available from:

http://home.howstuffworks.com/nail-gun.htm. 50. Can Crusher. 2007 [cited 2013 August]; Available from:

http://www.digitaldandt.org/db/index.php/casestudy/show/1318. 51. Modern, P.S. Material Science. 2008; Available from:

http://www.silicontraption.com/414pope/blog/2008/12/blog-post.html. 52. Orthopaedics, S. Instructions for Cleaning, Sterilization, Inspection and Maintenance

of Orthopaedic Medical Devices. 2012 [cited 2013 May]; Available from: http://literature.ortho.stryker.com/files/LSTPI_B.pdf.

101

11. APPENDICES

APPENDIX: 1

SURGEONS SURVEY RESPONCE

��������������� ��������������������������������������������������������������

������

������ ��

������ !

������ �� �����������������������������

�������������� � �������

!"�#$%$&'$(����� "��!�������%���"�������)������&��������%��������

!"�#$%$&'*$������� "��!�������%���"�������)������&��������%��������

���������������"��#�

+ !"�#$%$&'$(����� "��!�������%���"�������)������&��������%�������� (���

� $%�����&&� �� �'#���'"'#�(�

' )��������� �� �'#��� "���*�

� +��� ,��-�$%����.�+������� �������-��$�+ ��/�'#���'"�/�(�

0 ���-�1�����-����������� ��/�'#���'"���*�

! $%����-+��� ,��-��������� ��!�'#����"���(�

/ ���� ,����%���� ��!�'#���0"0��*�

2�(�� �&����� ��!�'#����"#0�*�

� �%���� ��0�'#���0"'��*�

� $%�����3+��� ,��4-��%��������. ��0�'#���'"�0�*�

�# �%�����5 0#����� ,�� ��0�'#����"!0�*�

�� $%���� ����'#����"'/�*�

�' �%���� ��'�'#����'"���(�

�� &(�6�) ��$� ��'�'#����"�0�*�

�0 $%����-�+��� ,��-���������������� ��'�'#���!"! �*�

�! +��� ,���$%����.�+���������+���� ����'#���'"0!�(�

�/ �%����-���������������� ����'#���'"� �(�

� ���� ,����%�������������������� ����'#�����"##�*�

�� �%���� ����'#����"'!�*�

�� $%���� ����'#�����"!��(�

'# ��� ����'#����"�/�(�

'� $%���� ����'#���'"' �(�

'' 2��(�� -�&6+���-�&&� ����'#���'"#��(�

'� $%����-�+��� ,��-���������������� ����'#����'"#/�(�

'0 +��� ,��-�$%����-���������������� ����'#����#"�0�*�

'! ������-������ ����'#����"'��*�

'/ ���������*(������ ����'#����"0/�*�

' +��� ,���$%�����+�������������� ����'#����"0��*�

'� $%���� ����'#���/"'0�*�

'� �%���� ����'#���!"'!�*�

�# +��� ,���$%������������������� �������������� ����'#���0"�#�*�

�� &6+����*��-�2��(�� -�7������# ����'#���0"# �*�

�' $%����-�&������� ������� ����'#���0"##�*�

�� &(��1����� ����'#���'"'��*�

�0 �%���������-�%����� ������ ����'#���'"�!�*�

�! $%���� ����'#����"00�*�

�/ ������������ ������������ ����'#����"���*�

� $%����-�+��� ,�� ��#�'#����"0��(�

�� $%����-����������� .�+��� ,�� ��#�'#���'"!0�(�

*������&����� ��������

��������������� ��������������������������������������������������������������

'�����

�� $%����-����������� .�+��� ,�� ��#�'#���'"!0�(�

�� $%����������8� ���9������ ��#�'#����"�#�(�

0# +��� ,��-�$%�����:0#-�+���������+���� ��#�'#����'"0��(�

0� +��� ,��-�$%�����++ ��#�'#����'"���(�

0' +��� ,���$%�����+��������-�)������&(��&�6& ��#�'#�����"���*�

0� +��� ,��-�$%���� ��#�'#����#"!!�*�

00 2�(�� -�&�����-���������������� ��#�'#����#"�'�*�

0! +��� ,��-�$%�����:0#�����-����������� ��#�'#����#"'��*�

0/ *���+�������������� ��#�'#����#"#/�*�

0 $%�����:0#���������������� ��#�'#����#"#/�*�

0� +��� ,���$%���������-�+���� ��#�'#����"' �*�

0� $%���� ��#�'#����"���*�

!# ����������������������� ��#�'#����"#��*�

!� $%����-�+��� ,�� ��#�'#����"#/�*�

!' ���� ,���5 0#��%������������� ��#�'#����"0'�*�

!� $%����-�&6�����*�� ��#�'#����"'/�*�

!0 2���� �&�����-������������ ��#�'#����"�'�*�

!! �6����-������ -����������������-����� ��#�'#��� "!'�*�

!/ &�+�$��+�* �;$++�+�$$;�2$(<= ��#�'#��� "0!�*�

! +��� ,���$%�����6�+��+���� ��#�'#��� "�/�*�

!� &(���������� ��#�'#���/"!/�*�

!� $%�����+��� ,��-���������������� ��#�'#���/"00�*�

/# $%����-�&������� ��#�'#���/"���*�

/� $%���� ��#�'#���!"!0�*�

/' +��� ,��-�$%����-�+���������+�����6������������� ��#�'#���!"0��*�

/� $%����-�+��� ,���-���������������� ��#�'#���!"0��*�

/0 +��� ,���$%�����+���������+���� ��#�'#���0"0��*�

/! >�������� ��#�'#���0"'��*�

// $%���������-�+��� ,�� ��#�'#���0"'��*�

/ +��� ,���6�$%���� ��#�'#����"! �*�

/� $%�����3+��� ,��4�����*���3?� 4 ��#�'#����"���*�

/� 2��(�� �&������7���� ��#�'#����"���*�

# $%���� ��#�'#����"#0�*�

� $%����-�&(� ��#�'#����"#��*�

' �%���� ��#�'#���'"0/�*�

� �+�#�1����� ��#�'#���'"' �*�

0 +��� ,���$%��������� ��#�'#���'"''�*�

! &6+����2��(�� ��#�'#���'"�#�*�

/ ���� ,����%���� ��#�'#���'"##�*�

+��� ,���$%���� ��#�'#����"!��*�

� ���� ,����%�������������������� ��#�'#����"0 �*�

� $%����������� ��#�'#����"0'�*�

�# )�������+�#�&�����&���� ��#�'#����"�/�*�

�� $%�����3+��� ,��4���&(��3)�����4���������������� ��#�'#����"�!�*�

�' 2��(�� �&������*���&&� ��#�'#����"�#�*�

�� 2�(�� �&������������ ��#�'#����"#��*�

�0 �%���� ��#�'#����"#��*�

�! &(��)�����-�79������ ��#�'#����"#��*�

��������������� ��������������������������������������������������������������

������

�! &(��)�����-�79������ ��#�'#����"#��*�

�/ 2�(�� �&����� ��#�'#����'"!��*�

� +��� ,���$%�����7�����%�++ ��#�'#����'"!/�*�

�� &��������� �� ��#�'#����'"!!�*�

�� $%���� ��#�'#����'"!��*�

�# �%���� ��#�'#����'"!'�*�

�� &(�-�)�����-�&&� ��#�'#����'"0��*�

�' &+����*��-�2���� -���������������� ��#�'#����'"0��*�

�� �������@>���� ����$%�����:�0#�A79������ ��#�'#����'"0��*�

�0 ?� �B����9 ��#�'#����'"0!�*�

�! �%�����������������C����� �� �'��'#���!"���*�

�/ $%����-+��� ,������������������-�����)��������������������� �'0�'#���/"0 �*�

� �%���� �'��'#����#"'/�(�

�� +��� ,��-�$%����-���������������� �'��'#����'"00�(�

+ !"�#$%$&'*$������� "��!�������%���"�������)������&��������%�������� (���

� 2���� -�&����-��������� ���#�'#���0"!��(�

' &���� �� �'#���'"'#�(�

� >����-�������������*��� ��/�'#���'"�/�(�

0 ����������-�������������� ��/�'#���'"���*�

! ���� ,���������� ��!�'#���0"0��*�

/ �����9� ��0�'#���0"'��*�

2�(�� �+������������������� ��0�'#���0"'��*�

� &�����(��������32���� 4 ��0�'#���'"�0�*�

� ������������ ,�� ��0�'#����"!0�*�

�# ����� ��'�'#����'"���(�

�� ����������� ��'�'#�����"''�*�

�' ) ��$���;��*($� ��'�'#����"�0�*�

�� >�������-�>�>����-�������� ��'�'#���!"! �*�

�0 2�(�� �&����.��������� ����'#���'"0!�(�

�! �������-����� ,��-���)B ����'#���'"� �(�

�/ &���� ����'#�����"!��(�

� &����-������ �3���9�������������4-��� ���9� 3��������������������4 ����'#����"�/�(�

�� &���� ����'#���'"' �(�

�� ����� ��������������� ����'#�����"!��*�

'# �����-������ ����'#����"'��*�

'� ������������� ����'#����"0/�*�

'' ��������*�������&��������� ����'#���/"'0�*�

'� ����� ����'#���!"'!�*�

'0 &����-�2��(�� -��������� ����'#���0"# �*�

'! &���� ����'#���0"##�*�

'/ ��������������-������������-��������������-������������� ����'#���'"�!�*�

' �����-������ ��������� ����'#����"���*�

'� +���������������-�*����9� -��������� ����'#����'"#��*�

'� 2���� -�&����-��������� ��#�'#�����"0��(�

�# +��� ,��-�����������-������������) ��#�'#���0"!��(�

�� *������-�+��� ,�� ��#�'#����"0��(�

�' (�� �����-����9����������-������������������������� ��#�'#���'"!0�(�

�� ��������������8������������� ��#�'#����"�#�(�

��������������� ��������������������������������������������������������������

0�����

�� ��������������8������������� ��#�'#����"�#�(�

�0 )������&;+��� ��#�'#�����"���*�

�! 2���� -�&���� ��#�'#����#"!!�*�

�/ +��� ,��-��������������-���� ���C����� ������ ��#�'#����#"'��*�

� +;�������������� ��#�'#����#"#/�*�

�� 2�(�� �&���� ��#�'#����#"#/�*�

�� &�������������� ��#�'#����"���*�

0# �������-������ ��#�'#����"#/�*�

0� &���� ��#�'#����"'/�*�

0' 7���������&����������������������� ��#�'#����"�'�*�

0� &7�* ;�� �*� <��2$(<= ��#�'#��� "0!�*�

00 )����������+;�6�������������� ��#�'#��� "�/�*�

0! &(��)����� ��#�'#���/"!/�*�

0/ 2���� -�&����-���*�/:0 ��#�'#���/"00�*�

0 *������������� ��#�'#���/"���*�

0� )������B�� ��#�'#���/"#!�*�

0� &���� ��#�'#���!"!0�*�

!# &����-���(�� -��������� ��#�'#���!"0��*�

!� &������� ������� ��#�'#���0"'��*�

!' +��� ,���6�*������ ��#�'#����"! �*�

!� +;�(����3+A�4 ��#�'#����"���*�

!0 (���������� ��#�'#����"#0�*�

!! 2���� �&���������-�2���� �(����������� ��#�'#���'"! �*�

!/ &�����2��(�� ��#�'#���'"' �*�

! +��� ,���*����������� ��#�'#���'"''�*�

!� &�����2��(�� ��#�'#���'"�#�*�

!� D��� ����9 ��#�'#���'"##�*�

/# &������������� ��#�'#���'"##�*�

/� 2���� �&���� ��#�'#����"!��*�

/' ���� ,������������������������ ��#�'#����"0 �*�

/� ��� ��#�'#����"0'�*�

/0 �������������, ��#�'#����"#��*�

/! )�������;������ ��#�'#����"#��*�

// 2�(���&���� ��#�'#����'"!��*�

/ E��9������������� ���� ��#�'#����'"!!�*�

/� ����� ��#�'#����'"!'�*�

/� �����,-��;�������2�(�� �)������������� ��#�'#����'"0��*�

# &�����2���� ��������� ��#�'#����'"0��*�

� �7 ��#�'#����'"0��*�

' ���������������� �'��'#���!"���*�

� &����������+��� ,�����������-���������+��� ,�����������-����������&������������-����������)�������������� �'0�'#���/"0 �*�

0 ������� �'��'#����#"'/�(�

! &�����6��������� �'��'#����"!'�*�

��������������� ��������������������������������������������������������������

!�����

�,����-�������.����%�'$/!�*�����

-�������.�����!0$��������������12�����

� � ��������������3

�������������� � �������

#�4����#���� 5��6�

!

55��6�

!0

�,����

00

76�,��

'0

��67�

�

�

#

��� ����������� ,,����

��

5�����

0#

8���8�

�0

���7��

��

��

#

�

!

#���� � ���,�

/

���,��

!�

�,�,6�

/�

���75�

/

8����

!

�

��

F�'��� '��� �'�� �/�� G��/��

#�4���

#����

��� �����

�����

#���� �

#H '#H 0#H /#H �#H �##H

� 9�,��� ,��� 7,�� 7��� :�7��� ���������������

��������������� ��������������������������������������������������������������

/�����

57�7�� �#

7��5� 0

������ ��

,����� '�

�7� �����; ������������������

��������������

�������������� � �������

2����� ��

����� ��

*������

������<*������

���������������"��#�

2����� ��

����� ��

*������

������<*�����

�

#H '#H 0#H /#H �#H �##H

*������&����� ��������

��������������� ��������������������������������������������������������������

�����

5�76� �

,����� '�

������ '

�6���� ������=���;�� �� � ������;�����

������������������

�������������� � �������

9�����

����

:�����

���������������"��#�

9�����

����

:�����

#H '#H 0#H /#H �#H �##H

*������&����� ��������

��������������� ��������������������������������������������������������������

������

���� �#�

�8���� ����������� ��������������"�����

���>��� ������4���

�������������� � �������

.����������!�������

���� �#�

+ !"����������������� "����� (���

� �� ��������������� ��0�'#���0"'��*�

' ����-���������������������������������9����������������� ����'#�����"##�*�

� ���������9��������5 �������@ ����'#����"�/�(�

0 ��������������������������� ��������� ����'#���/"'0�*�

! ����������������.� ��������������� ����'#���0"# �*�

/ ������� �������-��������������� ��������� ����'#���0"##�*�

�������������9�������������9����� ��#�'#����"#��*�

� ��9����������9��5 ��������������������� �>�����,�������������������������� ����� . ��#�'#����"�'�*�

� (���������������������� �������������������������-�������������������������������� ������ ��#�'#���!"0��*�

.���������

!�������

#H '#H 0#H /#H �#H �##H

*������&����� ��������

��������������� ��������������������������������������������������������������

������

���!"�����������.����������!�������)

��� ��������-������������&��4����"

����������������������1%���� �������-����

������� ������������"���"����� ?�"�������

���4�����)�����&��4����"�!������� ������

������������������"����� ?�"������"������ ;�)

�����������������������? �����"�������� ��

��������� ��3

������������5� � ������,

%$'�*�<�* ;� 7���7�

�

�5�7��

0

7���7�

�

��

#

6�78�

�

�

'�

%$'�*�<�%������� ,���8�

�

,��

��

66��,�

'�

5����

!

6��,�

�

�

/!

%$'�*�<�.��=� 67�58�

7��,8�

!

���58�

�

��,8�

�

��

#

�

�/

#$/�%!#�<�* ;� 68�

��

�5�8��

,5�8��

��

8�

'

8�

'

�

0#

#$/�%!#�<�%������� 6,�8��

'�

,6��5�

��

,���7�

�/

���8�

�

���8�

�

�

!0

#$/�%!#�<�.��=� 86�88�

/

,5�,5�

�

�����

�

�����

�

��

#

�

��

� ' � 0 G0

%$'�*�<

* ;�

%$'�*�<

%�������

%$'�*�<

.��=�

#$/�%!#�<

* ;�

#$/�%!#�<

%�������

#$/�%!#�<

.��=�

#H '#H 0#H /#H �#H �##H

� � , 7 6 :6 ���������������

��������������� ��������������������������������������������������������������

�#�����

�5�.��� ���������������� ����� ����� ����"

��� �����>��������=�������"�����4� �;

�����"������"����������>��� �@���� ��

������������� �����������>"����

����"�����1/�� ������"���)������A��B

������������� ��������A)�����A���B

�?�������� ��������A3

�������������� � �������

1�����4��3 ,��66�

��

�5�67�

��

������

��

5�76�

�

�6����

�/

���7�

'

8�8��

/

8�8��

/

7��5�

0

8�8��

/

�

�#�

�

�. �

1�����4��3

# � ' � 0 ! / � � �#

� � , 7 6 8 � 5 � � �� ���� �=���;��/�� �;

��������������� ��������������������������������������������������������������

�������

���2������� ����������� " ��"���������������

������� ��������� ������������ ����

��������� ���������� �����4�?�4�����

�������������� � �������

+ /�������� (���

� &������������9� ��������������������� ���#�'#���0"!��(�

' ��� �� �'#���'"'#�(�

� ������������������ ����������������� �� �'#��� "���*�

0 ����� ���� ��/�'#���'"�/�(�

! ��������� �� ��/�'#���'"���*�

/ ��� ��!�'#����"���(�

. ��!�'#���0"0��*�

� 6 ��!�'#����"#0�*�

� ���������������9�������� ��0�'#���0"'��*�

�# &���� ��0�'#���0"'��*�

�� ��� ��0�'#���'"�0�*�

�' ���������������������,� ��������������9����������������� ��0�'#����"!0�*�

�� ����������������� ������������ ����� �������������������"�+��� ����'#����"'/�*�

�0 ��������,�������������������������������������������������� ��������������� ����������������� �����

����.

��'�'#����'"���(�

�! � ��'�'#�����"''�*�

�/ �7�$ ��'�'#����"�0�*�

� ���I��������������� ����� ����-�����������������������9���������-����������� ��������������. ��'�'#���!"! �*�

�� ��� ����'#���'"0!�(�

�� ��������������������������������,��� ����������9���� �������������������� � ��,����-�3��J�,���4��������9

����������������9���������� ���

����'#���'"� �(�

'# ����������� ����'#�����"##�*�

'� ��� ����'#����"'!�*�

'' �������������������������� ������ ����'#�����"!��(�

'� J���������� � ������*����5 ���������6 ����� ��� ������������� ����'#����"�/�(�

'0 ��� ����'#���'"' �(�

'! B���� �������������� ����'#���'"#��(�

'/ $���� ����-�������9���������������������������9��� ���������-��������� ���������������������5 ���

����-�������9��������������������� ����.

����'#����'"#/�(�

' ��� ����'#�����"!��*�

'� ��������������������������� ����'#����#"�0�*�

'� �������������������� ��������� ����'#����"'��*�

�# +�������-����� ��������� -���������� ������D�������-����5 ������ �� ����'#����"0/�*�

�� ��� ����'#����"0��*�

�' ��� ����'#���/"'0�*�

�� ��� ����'#���!"'!�*�

�0 E������������������� ����'#���0"�#�*�

�! $��� ������ ����'#���0"# �*�

�/ ��������� �������� ����������9������������ ����'#���0"##�*�

� ��� ����'#���'"'��*�

�� ����������� ��������������������������������� ��9��������5 � ����'#���'"�!�*�

��������������� ��������������������������������������������������������������

�'�����

�� ��� ����'#����"00�*�

0# ����� ���������������������� ��������������.����������������������������������� ��9���������������9���������

��������������������������9���-�������D�����������������������@� �� ��������,������5 ��������������

���������������������������������� �����������������������������������@

����'#����"���*�

0� ��� ����'#����'"#��*�

0' �����K����� ��#�'#�����"0��(�

0� ��� ��#�'#���0"!��(�

00 6 ��#�'#����"0��(�

0! ���������������99����� ��#�'#���'"!0�(�

0/ ���������������������� +��������� ������� ��#�'#����"�#�(�

0 +������K���,����� ���� .� I���������������������������������������������������������� ����. ��#�'#����'"0��(�

0� ���������������. ��#�'#����'"���(�

0� ����������� ��#�'#�����"���*�

!# +���������������9 ��#�'#����#"!!�*�

!� ������������9����������� ��#�'#����#"�'�*�

!' *5������9����������1������������������������ ��#�'#����#"'��*�

!� +����-����� ���9��������������� ��#�'#����#"#/�*�

!0 ��� ��#�'#����#"#/�*�

!! � ; ��#�'#����"' �*�

!/ ) ��#�'#����"���*�

! ��� ��#�'#����"#��*�

!� �������������������������������� ��#�'#����"#/�*�

!� <���� ������� ��#�'#����"0'�*�

/# � ��#�'#����"'/�*�

/� ���������������������������������������� ����� � ������������� �����������������������������������9

��� �����9��������������������.����� ������������������������������� ����������������������������������

������������-�������������� �������������������������������������9�9��.�����9�������������

>�����,��������K������� ������������������������������5 ��.

��#�'#����"�'�*�

/' �����K������ ���� ����������L���������������������"�������������������������-�&������� ��#�'#��� "!'�*�

/� �7�$ ��#�'#��� "0!�*�

/0 ����� ����� ������������������� ������ -���������������� ������K��������������������� ������ ��#�'#��� "�/�*�

/! ��� ��#�'#���/"!/�*�

// ��� ��#�'#���/"00�*�

/ ���I������������ �������,��9���������������������������5 ����� ���� ��#�'#���/"���*�

/� ��� ��#�'#���/"#!�*�

/� ��� ��#�'#���!"!0�*�

# ����� �������������������� ��#�'#���!"0��*�

� ��� ��#�'#���!"0��*�

' ������������������������ ������������������� ��#�'#���0"0��*�

� 2�I���������������������������,��������� ��#�'#���0"'��*�

0 ��� ��#�'#���0"'��*�

! ��* ��#�'#����"! �*�

/ M������-�������������������������������,� ��#�'#����"���*�

2�I���������@ ��#�'#����"���*�

� ;;���������9���5 ��� ��#�'#����"#0�*�

� $���� ����.�&�����-���������.�L������� ����������� ���������������������������������� ��#�'#����"#��*�

�# ��� ��#�'#���'"! �*�

�� ����� ���� ��#�'#���'"0/�*�

�' ��� ��#�'#���'"' �*�

��������������� ��������������������������������������������������������������

�������

�� ��� ��#�'#���'"''�*�

�0 �������������9�� �������������������������� ���������� ��#�'#���'"�#�*�

�! ������������������������� ��#�'#���'"##�*�

�/ ���,���������������,����������9.��������������� ������������,. ��#�'#���'"##�*�

� *�9��9� ��#�'#����"!��*�

�� ��� ��#�'#����"0 �*�

�� ����������������������������,� ��#�'#����"0'�*�

�# �� ��������������3���� ���� �������94���������������������I���,I������9��������� ����5 �������������.�

��5 ��������������������������������� ������������� ������������ ����.�������9���������������������

������������������������������������������������ ����������.� ����������������������,������

� ���� �����I��5 � ��I� �������������� .�-���������� ������������5 ����������������9����������.���

���������������������������������������,������������� ����5 �������������������������������������9�

��������5 �������9�������������.

��#�'#����"�/�*�

�� ���.�������������������������,�� �����������������������������������5 ����.� ���� ������5 ��

���������9�������������������������-������������5 ������� ���������������������������

��#�'#����"�!�*�

�' ������� ��#�'#����"�#�*�

�� ��� ��#�'#����"#��*�

�0 ��� ��#�'#����"#��*�

�! ��� ��#�'#����"#��*�

�/ ��� ��#�'#����'"!��*�

� ����K��������� �������������������� ��#�'#����'"!/�*�

�� ��� ��#�'#����'"!!�*�

�� (�5 ���������������� �� ��#�'#����'"!��*�

�## ��� ��#�'#����'"!'�*�

�#� +�������,���������� ����������������. ��#�'#����'"0��*�

�#' &�����6������������9���#������������������-���������� ��������������������������9������� ��#�'#����'"0��*�

�#� ��� ��#�'#����'"0��*�

�#0 ��* ��#�'#����'"0!�*�

�#! . �'��'#���!"���*�

�#/ �����������������������1���������5 �����9����������������� �'0�'#���/"0 �*�

�# ���9������������������������������������������������5 ����������������� �'��'#����#"'/�(�

�#� ���� ������-����%�����5 � �'��'#����'"00�(�

�#� ������ ��������9�������������$������N�����N����������������� ��������� �'��'#����"!'�*�

115

APPENDIX: 2

PDS [10]

116

1. Performance

1.1 Must axially aligned seating of head on neck taper axis prior to impaction

1.2 Impact must be delivered in axial alignment with neck taper axis

1.3 Deliver impact force of between 4KN and 6KN, adjustable to 0.5KN

1.4 Must try to isolate majority of impact to head/neck taper junction

2. Customer

2.1 Must be able to facilitate a range of different head sizes (Determine using Surgeons Survey)

2.2 Must be able to fit into the exposed cavity in the patient created by the incision (Surgeons

Survey will determine the exact figures)

3. Medical Standards

3.1 Must comply with ISO13485:2003/AC:2007, has been classified as Class 1 Medical Device

4. Environment

4.1 Withstand regular exposure to temperatures up to 131 Degree C, during autoclave

sterilization as per EN ISO 17665-1:2006 [52]

4.2 Resist corrosion from saline, blood and cleaning detergents

4.3 Handle being thrown onto tray or dropped from approx. chest height and resist indentation

from other metal objects during cleaning and use

4.4 During Manufacture: Cannot be contaminated by any animal by-products, take note for

cutting fluids, solvents, lubricants, acids (plating and cleaning) to prevent transmission of

Creutzfeldt–Jakob disease [33]

4.5 During Storage: kept in trays conforming to ISO 11607-1, CE Mark or FDA clearance [52]

5. Maintenance

5.1 Must be low Maintenance

5.2 Must be easy to disassemble, reassemble and be convenient to sterilize and store

5.3 Minimise number of parts

5.4 Indicate disassembly on the device for ease of use or make it intuitive enough to use so that

it does not require instructions

117

5.5 Make  assembly  and  disassembly  “fail  safe”,  i.e.  design  for  error

5.6 Preferably disassembly and reassembly does not require tooling

5.7 Must be able to be cleaned via autoclave [52]

5.8 Must be able to use medical grade lubricating oil suitable for steam sterilization, if lubrication

is required

5.9 Product   should   include   “smart”   design   features   that   indicate   clearly to the maintenance

provider when any parts need to be replaced (such as a line mark on the impactor surface if it is

prone to wear)

6. Materials

1.1 Stainless Steel, for cost and ease of manufacturing and sterilisation

7. Safety

7.1 Carry out a Risk Analysis as per the methods recommended in BS ISO 14971:2012

“Medical  Devices.  Application  of  Risk  Management  to  Medical  Devices”

7.2 Address the usability of the device by following BS EN 62366-2008  “Application  of  Usability  

Engineering to Medical Devices”

7.3 Minimise any crevices or rough surfaces where it may be difficult to clean or dry after

cleaning to ensure effectiveness of cleaning

8. Testing

8.1 Use Head Pull-Off test ISO 7206-10 and Head Twist-Off test ISO 7206-9 to judge success of

device

9. Ergonomics

9.1 Must be able to be operated with two sets of gloves on

9.2 Consider required lighting, force required to grip and operate

9.3 Consider if the device can be operated with one hand as opposed to both hands

10. Weight

10.1 Estimated target weight or limits, source from ergonomic data

118

11. Aesthetics

11.1 Consider colour, shape, form and texture of finish. (could be influenced if an external

company wants the device designed for a particular hip model)

12. Customer

12.1  Gather  surgeon’s  opinions or expectations face to face, question and answer surveys etc.

Make a questionnaire for surgeons

13. Manufacturing & Manufacturing Facility

13.1 Device cannot be manufactured using any source of animals; this includes animal based

lubrications used for machining

13.2 Device can be manufactured internally in the University of Bath

14. Disposal

14.1 Consider the disassembly and disposal of the device/materials after it has reached the end

of its life cycle

14.2 Recyclability of the materials used in the final device

14.3 Carbon footprint generated by the manufacturing processes etc.

15. Product life Span

15.1 Approx. 5 years

16. Life in Service (performance)

16.1 Used 6 times per day, 5 times per week, for 5 years (approximation)

17. Installation

17.1 Consider the installation of the head into the device to deliver the impact and the spatial

constraints with which the device will have to work (i.e. within minimal invasive or standard

surgery)

17.2 The device must be able to get itself into position within the access space allowed (i.e.

within the confines of the incision)

119

18. Quantity

18.1 Low volume, when compared with mass produced goods which sell millions

19. Documentation

19.1 Keep everything documented in a logical electronic filing system that coincides with the

progressive Steps of the project

20. Legal

20.1 Consider  product  liability   legislation  and  the  potential  for  “product  defect”   [33], in terms of

not constraining the operation of the device to prevent possible error or misuse of the device.

20.2 Check legislation for product liability

21. Reliability

21.1 Design for low friction in parts

21.2 Design for low number of parts

21.3 Design for high quality tolerances and precision manufacturing

22. Patents, literature and Product Data

22.1 Check for the possibility of patent clashing

23. Competition

23.1 Investigate into existing or similar product to do the same or similar tasks to this proposed

device and see how this current PDS may vary with that for the other products and make sure

that this PDS has not overlooked anything [33]

120

APPENDIX: 3

SPRING SPECIFICATIONS

!

!

Quantity!1!required!

Price!quoted!over!the!phone!=!£14.11!each!(plus!post!and!packaging!of!£5.99)!

Total!=!£20.01!

(To!be!charged!to!Account!KBHMEIXLE,!as!per!Tony!Miles!request)!

122

APPENDIX: 4

SOLID MODELLING FOR TEST RIG

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

150

20

M10

M10

M10

M10

A

A SECTION A-A

O120

STEEL

NONE

Robin Maguire 08/08/2013

MODULAR HIP IMPACTOR DEVICE

BASE PLATE (Scale 1:1)

08/08/2013 R.M.0

1 0

2

M8 M8

O17

O89,4

16

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

SIDE VIEWPLAN VIEW

STEEL

NONE

Robin Maguire 08/08/2013

MODULAR HIP IMPACTOR DEVICE

PILLAR (Scale 1:1)

08/08/2013 R.M.0

2 0

170M10 (full length of bar)

*** QUANTITY 4 PILLARS ARE REQUIRED ***

16

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

STEEL

NONE

Robin Maguire 08/08/2013

MODULAR HIP IMPACTOR DEVICE

Bottom Cap (Scale 1:1)

08/08/2013 R.M.0

3 0

PLAN VIEW

FRONT VIEW

1010

A

ASECTION A-A

O10

O10

O10

O10

O10

O10

O10

O10

M3

M3 M312

0°

41

150

Hole depth 9mm, thread depth 7mm

5

O21

O25

O34,5

O41

120

68

16

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

NYLON

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

BOTTOM BUSHING(Scale 2.5:1)

09/08/2013 R.M.0

4 016

A

ASECTION A-A

O15

O 21O 25

155

5

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

BOTTOM BUSHING PLATE(Scale 2.5:1)

09/08/2013 R.M.0

5 0

A

A

SECTION A-A

5

O 21O 34,5

40

120°

120°

5,5

O 3

O 3 O 3

R2,7

5

R2,75 R

2,75

3

16

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

BOTTOM DISC(Scale 1.5:1)

09/08/2013 R.M.0

6 0

A

A

SECTION A-A

8

O89

O68

O50

O 10

O 10

O 10

O 10

16

2

27

2

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

IMPACTOR ROD TIP(Scale 1:1)

09/08/2013 R.M.0

7 1

A

A

SECTION A-A10

563

6

O 35O 22

15

6

M10

M4

1215 3

13/08/2013 R.M.1 Lengthened tip & added bores to hold contact materials

16

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

IMPACTOR ROD BODY(Scale 1:2)

09/08/2013 R.M.0

8 1

A

A

SECTION A-A15

515

556

O 18

18

M10

12

6

4,5

13/08/2013 R.M.1 Reduced diameter 12.5mm to 12mm, to reduce weight

16

165180

195

16

3146

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

SIDE VIEWPLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

SPRING TUBE(Scale 1:1)

09/08/2013 R.M.0

9 0

O 41

O50

16

248

22

O 46

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

TOP DISC(Scale 1:1)

09/08/2013 R.M.0

10 0

A

A

SECTION A-A

8

O68

O 50

23

30

O 10

O 10O 10

O 10

O6

16

89

2

54

2

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

TOP BUSHING PLATE(Scale 2.5:1)

09/08/2013 R.M.0

11 016

A

A

SECTION A-A

O 24O 34,5

R 2,75

R2,75 R

2,75O 3 O 3

O 3

5,5

120°

120°

5

40

3

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

NYLON

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

TOP BUSHING(Scale 2.5:1)

09/08/2013 R.M.0

12 0

O 18

O 24

O 28

155

5

16

A

A

SECTION A-A

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

TOP CAP(Scale 1:1)

09/08/2013 R.M.0

13 1

A

A

SECTION A-A

515

30

23

O6 O

10

O10

O10

O10

O24

O28

O41

O 34,5

5 15

M3, Hole depth 9, Thread depth 7

120°

M3

M3

M3

89

12/08/2013 R.M.1 Updated to add large diameter dimension

34

16

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

RELEASE LEVER(Scale 1:1.25)

09/08/2013 R.M.0

14 016

ISOMETRIC VIEW (Scale 1:1)

AA

SECTION A-A

R2

R2

O 6

133

2728

16

8

8

6

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

3X NYLON,3X POLYETHYLENE

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

MATERIAL TIP(Scale 5:1)

13/08/2013 R.M.0

15 0

O 6O 12

512

16

A

A

SECTION A-A

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

REF. Parts List

NONE

Robin Maguire 09/08/2013

MODULAR HIP IMPACTOR DEVICE

ASSEMBLY + PARTS LIST(Scale 1:2.5)

09/08/2013 R.M.0

16 1

A

A

SECTION A-AFRONT VIEW13/08/2013 R.M.1 Updated to include Material Tip

16

ItemNumber

Title Material Quantity

1 Base Plate Steel 1

2 Pillar Steel 4

3 Bottom Cap Steel 1

4 Bottom Bushing Nylon 1

5 Bottom Bushing Plate Steel 1

6 Bottom Disc Steel 1

7 Impactor Tip Steel 1

8 Impactor Body Nylon 1

9 Spring Tube Steel 1

10 Top Disc Steel 1

11 Top Bushing Plate Steel 1

12 Top Bushing Nylon 1

13 Top Cap Steel 1

14 Release Lever Steel 1

15 Material Tip Nylon,Rubber &PE

3x N, 3xR, 3x PE

24

113

1

41

51

61

71

81

91

101

111

121

131

141

151

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 17/08/2013

MODULAR HIP IMPACTOR DEVICE

TEST FIXTURE 1(Scale 1:1)

17/08/2013 R.M.0

X 0X

A

ASECTION A-A

O 31,7O 88

1020

25,5

22,5 O 12,88

83,8

22

ISOMETRIC VIEW (Scale 1:2)

R 6

7 3

41

30

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 17/08/2013

MODULAR HIP IMPACTOR DEVICE

TEST FIXTURE 2A(Scale 1:1)

17/08/2013 R.M.0

X 0X

A

A

SECTION A-A

7015

13

O45

O 50 O 14,5

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 17/08/2013

MODULAR HIP IMPACTOR DEVICE

TEST FIXTURE 2B(Scale 2:1)

17/08/2013 R.M.0

X 0X

O 14,5 O 45

15

A

A

SECTION A-A

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

FRONT VIEW

PLAN VIEW

STEEL

NONE

Robin Maguire 17/08/2013

MODULAR HIP IMPACTOR DEVICE

TEST FIXTURE 2C(Scale 2:1)

17/08/2013 R.M.0

X 0X

11

A

A

SECTION A-A

O 14,5 O 45

A

B

C

D

2345

A

B

C

D

5 4 3 2 1

MATERIAL

PROTECTIVE FINISH

ACTIVITY DATE

CHECKED

APPROVED

TITLE

DRAWING NUMBER SHEET No. ISSUE

UNIVERSITY OF BATH DEPARTMENT OF MECHANICAL ENGINEERING

THIS DOCUMENT IS COPYRIGHT AND THE PROPERTY OFTHE UNIVERSITY OF BATH. IT MUST NOT BE COPIED IN

WHOLE OR IN PART NOR DISCLOSED TO ANY THIRD PARTYWITHOUT PRIOR PERMISSION FROM THE UNIVERSITY.

UNIVERSITY OF BATH 2012©THIRD ANGLEPROJECTION

A3420mm x 297mm

DIMENSIONS IN MM SCALE AT A3 SIZE:DRAWN IN ACCORDANCE WITH BS8888

TOLERANCES UNLESS OTHERWISE STATEDLINEAR ±

ANGULAR ±SURFACE TEXTURE

REMOVE ALL BURRS AND SHARP EDGES0.5 MAX. RADIUS OR 45° CHAMFER

REVISION HISTORY

ISSUE DATE DRAWN APPROVED DETAILS OF CHANGES

DRAWN

NAME

SIZE

1

DO NOT TAKE MEASUREMENTS FROM DRAWING PRINTS. IF IN DOUBT: ASK.

OF

PROJECT

STEEL

NONE

Robin Maguire 17/08/2013

MODULAR HIP IMPACTOR DEVICE

TEST FIXTURE ASSEMBLY(Scale 1:2)

17/08/2013 R.M.0

X 0

FRONT VIEW

X

Distance req. for 6KN

Distance req. for 2KNDistance req. for 4KN

*** DISTANCE THROUGH WHICH THE SPRING CAN BE COMPRESSED IS CHANGED BY USING PART 2A ALONE (FOR 6KN), OR 2A+2B (FOR 4KN), OR 2A+2C+2B (FOR 2KN) ***

A

A

SECTION A-A

1313

22A

2B

2C