Redesigning Intramedullary Nail : to improve success rate

Redesigning Intramedullary Nail: to improve success rate

October 14, 2005

Tissue Engineering Design TeamTeam Members Erik Yusko – Leader Tony Wampole – BSAC Anna Moeller- BSAC Jon Sass- BWIG Danielle Ebben – CommunicationsClient Tass Dueland- DVM Ray Vanderby- ProfessorAdvisor Professor William Murphy

Problem Statement

To improve the intramedullary nail in an effort to decrease misalignments that lead to the inability to secure the nail to the bone.

Background Intramedullary nails are used to repair long

bone fractures Nails are inserted into the marrow of the bone

and secured into place by screws on the proximal and distal parts of the fracture

Most effective for clean fractures

Background Extension piece attached to nail Nail inserted in bone Jig attached to extension piece Screws put in place by using jig guides

Motivation

Poor alignment of jig guide with nail screw holes results in complications with inserting screws

Distal screws miss more often 4% of screws miss the target Need to strengthen extension piece/nail

interface

Client/Design Requirements Implement in current surgical procedure Maintain nail integrity Consist of only biocompatible materials Easily sterilized Reduce distal hole failure rate

Design 1: Extra Bars Decrease the width of

threaded screw Add 2 rods that go into the

nail New rods perpendicular to

screw holes

Proximal Screw Holes

Design 1: Pros and Cons

Pros: Moment arm

perpendicular to jig reduced

Doesn’t allow rotation Still easy to use

Cons: Screw is smaller Likely allow more

movement parallel to jig

May effect integrity of rod

Design 2: Conical Connection Force distribution increased Key prevent rotation around long axis Two areas were forces are now

opposing motion

Design 2: Pros and Cons

Pros: Easily implemented

into surgical procedure

Leaves most components unaltered

Moments in all directions should be reduced

Cons: May be difficult to

machine

Design 3: Double-Sided Screw Jig has conical hole Top extension screws into

middle and also into nail Middle has hollow center to

allow double sided screw through

Nut attaches middle to nail H head and notch align

holesConceptual; not to scale

Design 3: Pros and Cons

Pros: Will reduce

movement around top joint

Still align holes Stability of nail not

reduced

Cons: Increased difficulty

with more pieces Might not reduce

movement in second joint

Lengthens amount of nail left out of bone

Design Matrix

Design Simplicity Integrationintoprocess

Cleaning Cost PotentialEffective-

ness

TOTAL

(1-5) (1-10) (1-5) (1-5) (1-10) (5-35)

Extra Bars 4 9 5 3 7 28

ConicalConnection 3 8 5 3 8 27

Double-sided

Screw 4 7 5 2 7 25

Future Work

Decide on Final Design Determine Design Parameters Build & Test Prototype

References Rassman, W., Bernstein, R., McClellan, R., Jones, R., Worton, E.,

Uyttendaele, H. 2002. Follicular Unit Extraction: Minimally Invasive Surgery for Hair Transplantation [Online] http://www.newhair.com/resources/p_2002_fue.asp.

Willis, B. 2001 Hair! [Online] http://www.wcsscience.com/hair/page.html. [Company] Chemical Treatment, Internal Document, Rev. B. Mattmiller, Brian. (1998, April).  UW Biochemist solves riddle of collagen

stability.  Retrieved October 4, 2004, University of Wisconsin,http://www.news.wisc.edu/releases/print.php?id=2995

Youngerman-Cole, Sydney. Repair of the Vaginal wall (Vaginal Vault Prolapse. [Online] Retrieved October 7, 2004.http://my.webmd.com/hw/womens_conditions/tv1559.asp