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Orthopedic Adaptor Oral Presentation #4

This oral presentation discusses the design and development of an adaptor to connect a nail inserted into the femur to the knee prosthesis in cases of periprosthetic femoral fractures. The project aims for a universal, rigid, and practical adaptor to improve surgical outcomes.

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Orthopedic Adaptor Oral Presentation #4

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  1. Orthopedic AdaptorOral Presentation #4 • Kate Huddleston • Anna Duloy • Alexander Byall • Ashley Goodnight

  2. Schematic of Femur and Tibia

  3. Schematic of Knee with Prosthesis (pre-periprosthetic Fracture) 300,000 total knee replacements per year

  4. Schematic of Femur and Tibia post-Periprosthetic Fracture 7,500 Periprosthetic Fractures Per Year

  5. Project Definition • To design an adaptor that will connect the nail inserted into the shaft of the femur to the knee prosthesis, in the event that a periprosthetic femoral fracture has occurred

  6. List of Constraints • Hold the nail 5 degrees relative to the prosthetic joint • Universal • Maintain rigid structure • Irremovable knee prosthesis • Compatible with both right and left knee

  7. Project Background • Periprosthetic femoral fractures • These fractures occur: • when femur weakens during surgery • in patients with osteoporosis and rheumatoid arthritis • Patent Search - no current method to attach nail and prosthesis

  8. Importance • 300,000 total knee replacements per year. Of these there are 7,500 cases of periprosthetic femoral fractures (Incidence rate 0.6%-2.5%) • Target population: average age of patient is about 68, but age ranges from 42-92 years

  9. Cost • Cost of periprosthetic femoral fracture repair: • $30,000 (physician, hospital stay, radiology) • Cost of adaptor: • Exact price unknown at this point • Material decided as titanium, but specifications undecided

  10. Attachment Mechanism • Brainstorm on pros and cons of each • Practicality of design • Ease of use • Twist and lock was a possible mechanism:

  11. Initial Adaptor Schematic

  12. 2nd Adaptor Schematic

  13. Current Adaptor Schematic

  14. Adaptor Advantages • Significantly quicker procedure • 2 pins versus 4 • Less surgical dissection • Less blood loss • Better way to maintain alignment between femur and prosthetic knee

  15. Biomaterials • Factors to consider: • Compatibility with nail (same material) and prosthetic material • Oxidation reactions, Galvanic corrosion • Strength • Expense • Availability • Chosen Material: • titanium (Grade 5 or 6-4) - nail and adaptor • cobalt chrome - knee

  16. CAD Drawing for Current Schematic

  17. CAD Drawing with Applied Stresses • Analysis for 100 N applied to both sides • The maximum stress is 1500 MPa. • Yield stress for titanium 6-4 is 800 MPa, so our adaptor would break.

  18. Difficulties • Head of the screw – too big • Waiting for exact dimensions of the retrograde femoral nail • Difficultly measuring the prosthesis

  19. Prototype • Machine Shop: Cupples J&J Co., Inc. in Jackson, TN • Contact: John Landrum • Plastic prototype not possible • Titanium prototype wired with EDM • Not to cost over $200

  20. Current Status • Weekly meetings in Med Center Orthopedics Lab with Advisors • Attachment Mechanism • Details (dimensions) • Schematic • Specifications • CAD Drawing, Solidworks • Contacted Johnson & Johnson • Waiting retrograde femoral nail

  21. Future Work • Determine stresses on prototype • Continue work on CAD • Research mechanical properties of titanium 6-4 • Work on installation procedures • Continue meeting with advisors • Set up meeting with Dr. King for needs

  22. Acknowledgements • We would like to thank the following people for their help: • Dr. Limbird • Jeff Gordon • Sue Larson • Mike Bailey • Dr. King

  23. References • http://www.emedicine.com/orthoped/topic254.htm • http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthtkrperiprosthfrac.htm • http://www.eng.hull.ac.uk/research/medical/fracture_plate_intro.htm

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