Redesigning Intramedullary Nail : to improve success rate October 14, 2005

Tissue Engineering Design Team Team Members  Erik Yusko – Leader  Tony Wampole – BSAC  Anna Moeller- BSAC  Jon Sass- BWIG  Danielle Ebben – Communications Client  Tass Dueland- DVM  Ray Vanderby- Professor Advisor  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 holes Conce ptual; 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 DesignSimplicityIntegration into process CleaningCostPotential Effective- ness TOTAL (1-5)(1-10)(1-5) (1-10)(5-35) Extra Bars Conical Connection Double- sided Screw

Future Work  Decide on Final Design  Determine Design Parameters  Build & Test Prototype

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