VEXTEC Reliability Analysis of Above-the-Knee Leg Prosthesis Group 11 Aashish Bapat, April Boldt, Jason Deaner, Grainger Greene, Dani Shuck

Current Work:  Find component with highest rate of mechanical failure  Determine loads on component  Perform transfer functions to model the failure in other component Next: Use VEXTEX software to perform statistical analysis

Finite Element Modeling  Forces for transfemoral single-hinge prosthesis of a kneeling subject  Focusing on the knee joint/cap with titanium material  Next step: Create a model with actual prosthesis dimensions

Finite Element Analysis  Use MSC/Patran to create model with constraints and forces for kneeling subject  Perform finite element analysis with MSC/Nastran or ANSYS  Follow with microstructure analysis using VPS-MICRO™ from VEXTEC

“Prosthetic Loading During Kneeling of Persons with Transfemoral Amputation.”

Ultimate Goal  Compare current analysis techniques with results achieved using VEXTEC’s software  Figure out what VEXTEC can add to current analysis methods used by the prosthesis industry

Knee System  Manual Lock 1.2kg/2.64lbs including shin K1-k2 activity level Choose lock or stabilizing knee

Manual Lock Tech Information

Manual Lock Parts for Assembly

Foot System  Super SACH 25 cm Integral pyramid 0.36kgs/.79lbs K1-k2 level activity Differs from SACH in adjustable heel cushion

Orthotist (Dr. Gregory Mencio) & Prosthetist (Dr. Mark Watson) 1) What are the most widely used makes/models of above- the-knee prostheses? Popular makes: endolite, ossur, ottobock Models catered to individual lifestyle Work with interface of socket Exoskeletal: hard crustacean design Endoskeletal: inside all laminated foam, internal pylon 2)What basic advantages do the most popular models have over others in their design and or materials used? Steel vs. carbon fiber Carbon fiber: lighter, enhanced performance, more comfortable Steel: more durable Endoskeletal: lightweight

Orthotist (Dr. Gregory Mencio) & Prosthetist (Dr. Mark Watson) 3) What is the most common source of failure in these prostheses? Do they differ among models? Breakage at knee joint: inevitable, life depends on quality and activity of patient Loosening at socket: atrophy causes loosening around the socket Selection of prosthetic: Cost: approx $30, ,000 Activity: hydraulic versus geriatric patient Vets from Iraq receive new prostheses about every 2 years Cheaper models break down quickly, less comfortable, fewer “bells and whistles” 4) How common are mechanical failures in these prosthesis? Set screws often toggle and break Failure at knee linkage

Orthotist (Dr. Gregory Mencio) & Prosthetist (Dr. Mark Watson) 5) What kind of warranties (if any) come with above-the-knee prostheses? 0-3 years Most often 6 months – 1 year Warrantees = improves life of product 6) Do the prostheses manufacturers offer any technical support in your practice? New product education Insight on amputation and fitting for prostheses

Mark Watson: Orthotist/Prosthetist 7) How much time and money to these manufacturers spend on reliability analysis? Endless process for better/more durable models 8) What does their process for reliability analysis involve? Cheap models break down  insurance and prosthetists pay Engineers design durable models Summary: Materials tested, materials combined, models engineered, models tested, then human testing following FDA approval

Uncertainty  Mark Watson ultimately unsure about reliability testing Will provide contacts at Otto Bock and Ossur, others Team will contact manufacturers, design engineers to determine specific processes

Customer Report  Pratt Whitney Testing reduced to half Closed minded medical community ?  Lockheed Martin Warranty/Liability reduction a major revenue Medical Device trade shows Databases like oracle for testing data

Resources:  Magnissalis, Evangelos Et Al. “Prosthetic Loading During Kneeling of Persons with Transfemoral Amputation.” Journal of Rehabilitation Research and Development 36.3 (1999):  kl/eskmkl.html kl/eskmkl.html  %20Iss4%20Endolite%20Pros%20Prod%20Cat.pdf %20Iss4%20Endolite%20Pros%20Prod%20Cat.pdf  %20Iss4%20Endolite%20Pros%20Prod%20Cat.pdf %20Iss4%20Endolite%20Pros%20Prod%20Cat.pdf  kl/eskmkl.html kl/eskmkl.html  kl/eskmkl.html