Amp Philosophy Compatibility Mode 1199029758398641 4

8/3/2019 Amp Philosophy Compatibility Mode 1199029758398641 4

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Austin Moores ProsthesisIts Relevance Today

no aner a r s eo ar r un a wanConsultants

Choithram Hospital & Research Centre, Indore, India


2/79

Improper technique Desi n of Im lant

Design of instruments

THR dominated


3/79

hypertrophy of the bone all around.

months. success u ong s an ng eve op

some osteolysis of the bone.

Osteolysis in THR seen late and damgebecomes a problem


4/79

mechanostat of bone after implant surgery.

Proximal fixation at or above the level of

cancellization of cortical bone in the

.


5/79

the success of the surgery.

,

and allow the grafts in the fenestration to, -

device.

s preven s over- oa ng o ca car nosubsidence, no loosening, no failure.


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.

influences on bone strength and. .

1997;8:6070.

-----------------------------------------------------------

Bone loading - Bone strength

Bone modeling hypertrophy / normal

Bone remodelin h otro h / atro h

-----------------------------------------------------------


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Bone modeling by drifts

(A) An infants long bone with its original size

an s ape s own n so ne. o eep s s apeas it grows in length and diameter, modeling

r s move s sur aces n ssue space as e

dashed lines suggest. Formation drifts makean con ro new os eo as s o u some

surfaces. Resorption drifts make and control

new os eoc as s o remove one rom o ersurfaces.


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(B) A different drift pattern can correct the fracture

-.shows the endocortical as well as the periosteal drifts

that do the correction.

(C) How the drifts in B would move the whole segment

.

reduces the bones bending moments; it does not

, .

when and where they are needed, and they include

capillaries, precursor and supporting cells, and some

wandering cells. They are multicellular entities in thesame sense as renal nephrons, and they usually act to

m n m ze pea one s ra ns


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BMU Renal Nephron

Bone remodeling BMUs. Top row: an activation event on a bone

surface at (A) makes a packet of bone resorption begin

, .

The BMU makes and controls the new osteoclasts andosteoblasts that do this. Second row: this emphasizes the

amounts of bone resorbed (E) and formed (F) by completedBMUs. Third row: in these BMU graphs (G) shows a small

excess of formation over resor tion. H E ualized resor tion andformation as on haversian surfaces and in conservation-mode

remodeling.


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(I) A net deficit of formation, as in disuse-moderemodeling of endocortical and trabecular bone. Bottom

BMUs of the kind immediately above on the local bone .

needed and include a capillary, precursor and supporting

cells, and some wandering cells. They are multicellular

entities in the same sense as renal.


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implantation of an Austin Moore

SB Murphy, PS Walker and AL Schiller

J Bone Joint Surg Am. 1984;66:437- 443.

The calcar and proximal regions are

understrained because much of the loads

and moments are transferred to the bonearound the distal half of the stem.


14/79

-

resistance to axial force, whereas the distal halfof the stem may carry little axial load. The varus

moment on the stem is counteracted by forces at

the medial part of the calcar and the distal tip, ina more concen ra e manner an n a

cemented stem. The radiographic appearance

hypertrophy in the whole proximal area,

es eciall mediall , and local thickenin at a

point level with the tip of the prosthetic stem.


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,hemiarthroplasties have been reviewed in the

,

stem. Results from our finite-element analysis, - ,

the stresses in the stem are small because

bone are uncoupled and, consequently, do not

head and abductor forces.


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resultant bending moment is shared, high stressesin the stem are redicted such stresses are

inconsistent with the complete absence of fractures

of these prostheses. The results of the finite-element analysis further showed that loss of calcar-

collar support with proximal fixation through the

and stress shielding of the proximal medial cortex.


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The uncoupled prosthesis also may be modeled with

a car o ar uppor

a free-body diagram as a three-force member loadedat the head, stem tip, and in the proximal region. With

,

the stem tip, and thus the peak bending stress in the

-, .

If there is no calcar-collar support, proximal support

must be provided by some combination of integration

of bone in the fenestrations and wedging due to thelateral-medial taper of the device..


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Stresses on Stem

Stresses in the stem are largest when there is no

we g ng, ut g stresses eve op n t e

cancellous bone in the fenestrations. When there

, ,

stresses in the supporting cancellous bone can

be hi h additional roximal su ort throu h the

fenestrations substantially reduces these bone

stresses


19/79

Stresses on Stem

. If reduced stresses in the

stable device, these mechanisms

Moore prosthesis have not occurred

in normally loaded hips because

load was transferred primarily eitherthrough the collar or by wedging,

w a ona suppor a e

fenestrations


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-

Loose Prosthesis

a car a sorp on

Subsidence of the prosthesis oss o varus a gnment n t e cana

Acetabular cartilage erosion


21/79

Elderly

Wide canal

n er our con ro Faulty operative technique

Over reaming by improper Rasp

Improper selection of Implant


22/79

Effect of neck resection on torsional stability of cementless total hip replacement.

, , .

Biomechanical Research Laboratory, St. Louis, Missouri, USA.

Loosening of the femoral component in total hip

arthroplasty commonly results from inadequate

.

human cadaver femora to determine the effect of

-the femoral component. All specimens were prepared for

fixation with the Impact modular total hip replacement.

Each femoral diaphysis was overreamed 2 mm toachieve only proximal fixation. The specimens were then

v e n o groups o ve an mp an s were nser e

with the precision press-fit technique.


23/79

Without distal fixation, the femoral

com onent is hi hl de endent on roximalgeometry for resistance to torsional loading.

Preservin the femoral neck rovides an

effective means of resistance. Maintainingthe entire femoral neck most effectivel

reduces miromotion at low loads, but

maintainin the midshaft area of the femoralneck appears to most effectively control

micromotion at higher torsional loads.

Resection below the midshaft of the neckmarkedly decreases the torsional load-

bearing capacity of the proximal femur.


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-incidence of calcar resorption. Sufficient cementation

incidence of calcar resorption, as did neutral andvalgus positioning of the femoral component.

Loosening of the acetabular component occurred

more often in the group with calcar resorption. Middle-age pa en s an men were more prone o eve op

resorption of the calcar. Calcar resorption may be

.

operative technique is recommended, with emphasis

on correct val us or neutral osition of the femoral

component, a positive calcar-collar contact, and

improved cementation


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Proximal Fixation

Tips & Tricks

- .

Proper neck cut.

vo comm nu ng a car emor s.

Save at least 1cm of neck at Calcar Insert canal finder from Piriformis Fossa

, .


26/79

Proximal Fixation

Tips & Tricks

proximal femur without increasing.

Use a artery forcep in the prosthesis

,

rotation control during insertion.


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Proximal Fixation

Tips & Tricks

The most important area is the medial side nearcalcar. Graft should be inserted when nearly half of

the prosthesis has gone inside.

Fill the fenestrations of the prosthesis with bone

, .

The color of the implant should not over-hang on the

calcar.

If done properly, it should rest on the neck and willcompress the grafts.


28/79

-uncemented Austin Moore prosthesis is relatively

.

and consultants were not significantly different.

demanding operation; the prosthesis is difficult to

.

Greater selectivity should be exercised when

femoral neck fractures.


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(1)Inadequate length of the neck remnant (12

lesser trochanter to the resection margin at the

.

remnant was identified on postoperative,

trochanter to the level of the fracture on

.(2) Inadequate calcar seating (>1 mm)-measured

.

prosthesis collar seated on the medial calcar was

.


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(3) Difference in prosthetic head size compared

with the contralateral normal femoral head usincircular overlays-a diameter of prosthesis up to 2

mm lar er to account for articular cartila e was

considered satisfactory. If the contralateralfemoral head was not suitable for anal sis due to

disease or previous prosthetic replacement), the

i silateral femoral head on reo erativeradiographs was used for assessment of the

appropriate prosthetic head size.

(4) Intra-operative periprosthetic fracture- fractureclassification was conducted using the Vancouver

system.


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147 patients were treated with the unipolar

time period: 128 (87%) had surgery performed by

-

officers, 57% by training registrars, and 17% by

performed by a consultant surgeon.

patients; only 76 (52%) had no errors in

, ,(12%) had 2 errors, and

. .


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1: Injury. 2002 Jun;33(5):419-22.

Austin Moore hemiarthro last : technical as ects and their effects on outcome, in atients with fractures of the neckof femur.

Sharif KM, Parker MJ.

Orthopaedic Department, Peterborough District Hospital, Peterborough PE3 6DA,

UK. khalidsharif doctors.or .uk

In order to determine which technical aspects of the Austin Moore hemiarthroplasty

procedure affect the outcome, we reviewed 243 patients with a non-pathologicalintracapsular femoral neck fracture who had, Austin Moore uncemented

. - -

alignment of the prosthetic stem, calcar seating, length of the neck remnant,

leg length discrepancy and size of the head, compared with the contralateral femur.

All patients were followed-up for 1 year. Significant pain at 1 year and/or revisionof the prosthesis for loosening were considered as unfavourable outcomes.

Inadequate calcar seating was significantly associated with pain and revision

of the prosthesis (P = 0.04 and 0.01, respectively). Length of the neck remnant

. . ,

respectively). Difference in head size was associated with pain, but not withloosening (P = 0.01 and 0.08, respectively). The rest of the parameters were not

significantly associated with the outcome. We recommend that when inserting an

Austin Moore hemiarthroplasty, particular attention must be paid to the seating of

the collar of the prosthesis on the calcar and correct choice of head size.


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Injury. 2004 Oct;35(10):1020-4.

Critical radiolo ical anal sis after Austin Moore hemiarthro last .Yau WP, Chiu KY.Department of Orthopaedic Surgery, The University of Hong Kong, Queen Mary

Hospital, No. 102, Pokfulam Road, Hong Kong, PR China. [email protected]

treated with Austin Moore hemiarthroplasty (AMA). The clinical and radiologicaloutcomes were documented in a quantitative manner after 7 years follow-up of 144

patients. At the time of final follow-up, 52 patients had died and 48 patients were lost

to follow-up, leaving a total of 44 patients for analysis. Immediate post-operative

X-rays were studied for the initial alignment of prosthesis, the fit of the prosthesis

and the degree of osteoporosis. X-rays on latest follow-up were studied for evidence.

special surgery. It was found that hip pain was significantly related to subsidence

and pivoting of the prosthesis (P = 0.014 and 0.035, respectively).

Significant increase in subsidence was noted if the stem of prosthesis was not fitting

well within the shaft of femur (P = 0.006). When the patient was younger than73 years old at the time of operation, there was more subsidence of the prosthesis at

the final follow-up (P = 0.001). It was concluded that the fill of AMA within the shaft

.

patients with acute fracture of the neck of femur should be treated by methods other

than cementless AMA.

Injury 2004 Oct;35(10):1020 4


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Injury. 2004 Oct;35(10):1020-4.

Critical radiological analysis after Austin Moore hemiarthroplasty.

Yau WP, Chiu KY

was conc u e a e o w n e s a ofemur should be greater than 70% to avoid early

.

fracture of the neck of femur should be treated bymethods other than cementless AMA.Injury. 2002 Jun;33(5):419-22.

Austin Moore hemiarthroplasty: technical aspects and their effects on outcome, in

patients with fractures of the neck of femur.ar , ar er .

Inadequate calcar seating was significantly associated

with ain and revision of the rosthesis P = 0.04 and

0.01, respectively). Length of the neck remnant was alsosignificantly associated with these two outcomes (P =

0.05 and 0.023, respectively). Difference in head size

was associated with pain, but not with loosening

J Trauma 2001 Jul;51(1):84 7


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J Trauma. 2001 Jul;51(1):84-7.

The effect of intramedullary corticocancellous bone plug for hip hemiarthroplasty.

Kligman M, Zecevic M, Roffman M.

Application of a corticocancellous bone plug in uncemented

hi hemiarthro last for treatment of femoral neck fractures

can decrease the incidence of early thigh pain in the first 6

months.

Scand J Surg. 2002;91(4):357-60.

The long-term results of Lubinus interplanta hemiarthroplasty in 228 acute femoral neckrac ures. re rospec ve s x-year o ow-up.

Isotalo K, Rantanen J, Arimaa V, Gullichsen E.

, ,

diaphyse) angle and a longer stem compared to Thompson and

Moore implants. The need for resection of calcar cortex is also

limited. These biomechanical facts may explain the good long-

term results of Lubinus hemiarthroplasty.


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Loading of the calcar leading to Neck over hang & absorption


38/79

Impaction Grafting

Calcar Femoris

Day One


39/79

Tight Femoral CanalThree Point Fixation


40/79

Proximal Fixation

.

Proximal Fixation


41/79

14 years PO

Broken stem

Not a Failure


42/79


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Not a Failure

20 ears FU


44/79

Bone in the fenestration

A broken stem is not a failure


45/79

Too Much Valgus Too Mush Varus


46/79

u s ence

No proximal Fixation


47/79

Subsidence


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Ideal Prosthesis Fitting

or mo erate y w e cana1.Correct offset

.

3. Correct Varus setting4. Three oint fixation

For Narrow canal the junctionbelow the fenestrations is too much

,


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Intra operative error during AMP


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Intra-operative error during AMP

. .Weinrauch, P

pat ents were treate w t t e un po ar uncemente

Austin Moore prostheses over the time period: 12887% had sur er erformed b relativel unior

doctors-14% by senior medical officers, 57% by training

registrars, and 17% by principal house officers; 19 (13%)

were per orme y a consu an surgeon.

84 errors in implantation were identified in 71 patients;

onl 76 52% had no errors in im lantation while 52

(35%) had one error, 17 (12%) had 2 errors, and 2 (1.4%) had 3 errors.


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. . . .

188 patientsn ec on .

Dislocation 3.4%Loosening 3.4%

-


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- quality of lifepat ents average yrs

7% dislocation

4% deep infection

pros rus o

2% loosening of prosthesis

5 yrs -- > 60% mortality in both groups

move independently.


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Peri-prosthetic fracture

AMP was well fixed

Could not be removed


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Could not be removed


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. .

From University hospital of Cleveland Ohioourna o r rop as y

AMP Bipolar7% died(3 months) 11% died

.

(55 to 92) (60 to 94)


62/79

must be paid to theseating of collar of

e pros es s on

choice of head size.


63/79

be learnt.

Cost effective, well

patients

German article

154 AMP for 10 yrsAt 3yrs 46% community


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y y

35% non functionalambulance

Men had better than women

arr s p score -- yrs59 10yrs

.

10 yrs 7.7%Revision rate -- > 5 rs - 4.5 %

10 yrs 5.2%

A case of THR done 14 Years ago


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g

ow e s ow ng e orma onNo complaints A.M.P. 16 years ago.


66/79

satisfactory function in elderly

Average ortho surgeon can perform

set-up.

an e surgery e ore an asfor appropriate stem width according

o emora cana .


67/79

Summary

Carefully reaming in narrowfemoral canal.

No reaming in Osteoporotic

. Use bone grafts from femoral

Always fill the fenestrations

w one gra s.


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satisfactory.

THR cemented bi olar has ot their own

indications, & they are also not free from serious

complications.

AMP is Cost effective,

Bone cement can be used as last option.

Further improvement in the implant design isrecommended.


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Fracture N/F

AVN 1998

AMP working since then


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-

Friction failure emen sease

Design failure

Particle disease

Mechanical failure - Mechanostat

Proxima Depuya conservative meta h seal im lant


75/79

Proximal Fixation


76/79

Well fixed AMPProxima DePuy

AMP Still working


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Dont throw awa

t e

DISCLAIMER


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Information contained and transmitted by this presentation is

Choithram Hospital & Research centre, Indore, India, during last

25 years.It is intended for use onl b the students of ortho aedic sur er .Views and opinion expressed in this presentation are personalopinion.Depending upon the x-rays and clinical presentations, viewers

.For any confusion please contact the sole author for clarification.Every body is allowed to copy or download and use the material

.

arise out of this presentation.For any correction or suggestion please [email protected]

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Amp Philosophy Compatibility Mode 1199029758398641 4