Vextec reliability analysis of above the knee leg prosthesis
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VEXTEC Reliability 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’

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Vextec reliability analysis of above the knee leg prosthesis

VEXTECReliability Analysis of Above-the-Knee Leg Prosthesis

Group 11

Aashish Bapat, April Boldt, Jason Deaner, Grainger Greene, Dani Shuck

Company overview
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
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
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
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
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
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
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
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
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
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

Medical trade shows1
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

    • Over4,000 pharmaceutical and medical device manufacturers

  • Will look for more advice from Dr. Watson and other contacts

Interview with dr fitzsimmons
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 fitzsimmons1
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
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
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
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