VEXTECReliability Analysis of Above-the-Knee Leg Prosthesis

Group 11Aashish 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

Knee socket model

3 D model built in Pro/Engineer

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

Resources

http://www.devicelink.com/expo/west07/ http://www.devicelink.com/mddi/ http://www.pharmameddevice.com/