vextec reliability analysis of above-the-knee leg prosthesis group 11 aashish bapat, april boldt,...
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VEXTECReliability Analysis of Above-the-Knee Leg Prosthesis
Group 11
Aashish Bapat, April Boldt, Jason Deaner, Grainger Greene, Dani Shuck
Company Overview
VEXTEC’s reliability analysis capabilities: Unique approach with usage of ‘physics of failure’ and
‘material science libraries’ Funded by a Federal government grant Competitors tools are limited as they only use
statistical analysis
Current Customers: Aerospace & Automotive markets
Goal: Break into the Medical Device Sector
Reliability Analysis Technology Overview
Desktop Computational Reliability Model (DCRM) Predicts fatigue failure Simulates real material degradation models
How it works? Grain structure of materials given conditions Monte Carlo Probabilistic methods Modeling of this early crack behavior 3D Component Analysis
Project Goals
Predict reliability of above-the-knee prosthetic leg (Finite element analysis)
Material Geometrical Loading Available data on failure
Modify the design of Reliability analysis software for the prosthetic leg
Project Goals (contd.)
Market Analysis Potential Medical device manufactures
Testing cost and time reduction analysis Meetings with the medical device industry to
identify specific market needs Aid for FDA approval
FDA Potential tool for the FDA to run preliminary
design reliability analysis
Division of Work
Dani: Prosthesis model, Team Leader Aashish: Biomechanics Jason: MSC/PATRAN modeling, Finite
Element Analysis Grainger: Medical device market
research, manufacturing and professional contacts
April: Manufacturing and professional contacts
Prosthetic Leg analysis Journal of Rehabilitation Research & Development
Prosthetic Loading during kneeling Blatchford Manual Lock system for K1 – K2 activities 162 tests in prosthetic knee undertaken Critical Shear Forces and stress measure with sensors
Modeling the knee Unit
•Fatigue failure often observed at the Knee Unit
•Knee unit isolated and modeled
•Reliability analysis on three pins shown in the socket
•Once set up, similar analysis can be performed on the whole prosthesis to determine reliability
PSP Endo Stabilised Knee with Manual Knee Lock
Assessing the reliability of the Knee Unit
A 2-dimensional projection of the simplified ankle joint will be analyzed in MSC/Patran with MSC/Nastran or ANSYS.
The results will be used in VPS-MICRO to analyze the microstructure.
The goal is to see what VEXTEC’s software can add to the medical industry’s current analysis techniques.
Medical Trade Shows
Cannon Communications LLC: leader of trade show publications for medical manufacturing
MEDTEC Germany (Messe Stuttgart, Germany, Feb 27-March 1, 2007)
MD&M East (New York, NY, June 12-14, 2007) MEDTEC China (Shanghai, China August 28-30, 2007) MEDTEC Ireland (Galway, Ireland, September 19-20, 2007) BIOMEDevice (MD&M Event, San Jose, CA, October 3-4,
2007) MD&M Minneapolis (Minneapolis, MN, October 17-18, 2007) MD&M West (Anaheim, CA, January 29-31, 2008)
Medical Device and Manufacturing Trade Shows: Sponsored by Medical Device and Diagnositc Industry
http://www.devicelink.com/mddi/
Medical Trade Shows
Medical Design & Manufacturing West January 28-31, 2008 Anaheim Convention Center, CA Large-scale tradeshow, 1500 exhibiting companies in the $104
Billion medical device market Suppliers in cardiovascular, orthopedics, prostheses, etc.
Medical Design & Manufacturing East June 11-14, 2007 Jacob K. Javits Convention Center, New York City Mid-size tradeshow
Pharma Med Device April 24-26, 2007 Jacob K. Javits Convention Center, New York City Over 4,000 pharmaceutical and medical device manufacturers
Will look for more advice from Dr. Watson and other contacts
Interview with Dr. Fitzsimmons
Easier to get devices approved in Europe ISO standards less than FDA Perform physical tests with predetermined forces
Warranties are mostly guesswork Feet – 36 months Knee – 24 to 36 months Medicare recommends 5 year life for prosthesis Ultimately depends on activity level (0-4) 4 level cannot expect for device to last more than a year
Most failures from feet Below-the-knee prostheses more common than above-
the-knee, thus more feet likely to fail than knee’s
Interview with Dr. Fitzsimmons
List of manufacturers Otto Bock Ossur Endolite Ohio Willowood Medi Bulldog Tools Jim Smith Sales Euro International Fillauer
Otto Bock has 4-5 large facilities within U.S. Provided contact with Otto Bock
Phone Call to Otto Bock
Spoke with Scott Weber, Marketing Manager for Feet Units at Otto Bock Minneapolis office
Most prostheses exempt from FDA approval, use ISO standards Microprocessor knee unit is not FDA exempt
Physical testing is expensive and time consuming, lots of money wasted on testing incorrect prototypes
Exo-skeletal knee prostheses are vanishing from market
Feet units are more customized than Knee units, more failures in them also
Phone Call to Otto Bock (contd.)
They do use Finite Element Analysis to some extent in their reliability analysis Do not use statistical modeling, never heard of
Relex or Reliasoft Otto Bock goes above and beyond ISO standards
in their testing ISO would be a good resource for specific force
loads used on prosthesis units. Gave contact at Salt Lake City office
Sarah McCarviell, Head Engineer(?) All physical testing and design engineering done at
Salt Lake City office
Future Work:
Use VEXTEC’s VPS-MICRO software to perform analysis on knee joint for kneeling forces
Perform same analysis on same device for walking forces
Speak with design engineers at different prostheses manufacturers about applicability of VEXTEC’s technology
Speak with FDA Compliance Consultants about possible FDA usage/acceptance
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