Redesigning Intramedullary Nail : to improve success rate

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

Proximal Screw Holes Design 1: Extra Bars • Decrease the width of threaded screw • Add 2 rods that go into the nail • New rods perpendicular to screw holes

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 1: Pros and Cons

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

Conceptual; not to scale 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

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 3: Pros and Cons

Design Matrix

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 collagenstability. 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

Redesigning Intramedullary Nail : to improve success rate