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Lessons from Retrieval Analysis of Joint Replacements

3 rd ISOC Meeting - Bologna. Lessons from Retrieval Analysis of Joint Replacements. Tim Wright, PhD. Failure Analysis. Explain the unexpected. Retrieval Analysis as Failure Analysis. Retrieval Analysis has Other Purposes. Strengths

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Lessons from Retrieval Analysis of Joint Replacements

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  1. 3rd ISOC Meeting - Bologna Lessons from Retrieval Analysis of Joint Replacements Tim Wright, PhD

  2. Failure Analysis Explain the unexpected

  3. Retrieval Analysis as Failure Analysis

  4. Retrieval Analysis has Other Purposes Strengths Direct assessment of in vivo “real life” performance Early warning of unanticipated problems Justification for rational design changes Limitations “Failed” devices Clinical data sometimes unknown

  5. Retrieval Analysis at HSS Implants: OR  Pathology  Biomechanics Cleaned and cataloged: 77120601 Boxed and labeled (without patient identifiers) Entered into password-protected searchable web-based database (IRB Approved/HIPAA Compliant) Connected to TJR registries (CERT and CORRe) Yr Mo # Day

  6. . Retrieval Analysis as Postmarket Surveillance 55 /mc) 45 . Crosslinking of Polyethylene . 35 . . Wear Rate (mm3 25 15 5 0 5 15 0 10 Radiation Dose (Mrad) Courtesy of Harry McKellop, PhD

  7. Fatigue Wear and Fracture Rate of crack growth Cyclic crack driving force Bradford et al, CORR 2004

  8. Clinical Relevance? Reliance on Preclinical Tests Joint simulators Standardized tests

  9. THA Clinical Results 30% to 96% reduction at 2 – 5 yrs N = 37 in each group Patient-matched: age, wt, sex Dorr et al, JBJS 2005

  10. Retrieval Analysis • Examine cross-linked polyethylene acetabular liners for wear damage • Compare wear damage to that in a conventional polyethylene liner with identical design and same manufacturer

  11. Materials 79 conventional liners (Trilogy, Zimmer) 78 cross-linked liners (Longevity, Zimmer)

  12. Materials 79 conventional liners (Trilogy, Zimmer) 78 cross-linked liners (Longevity, Zimmer) 15X

  13. Fracture Conventional Poly and Cross-linked Poly 1 Incipient Crack 5 Incipient Cracks, 1 Rim Fx Schroder, et al., 2010 ORS

  14. Clinical Relevance? Reliance on Preclinical Tests Joint simulators Standardized tests

  15. Retrieval Analysis as a Design Tool Preclinical Testing Design Clinical Use Retrieval Analysis

  16. Posterior Stabilized TKA • Assure femoral posterior translation (in flexion) • Prevent femoral anterior subluxation (at high flexion) • Provide large ROM

  17. Anterior Impingement Occurs at: hyperextension low flexion angles Prevents posterior femoral translation increases stability causes wear & deformation Unintended articulation large contact stresses low contact area

  18. Retrieval analysis of a modern PS design 103 Retrieved Optetrak Tibial Components

  19. Methods 103 Retrieved Optetrak Tibial Components Examine all inserts for evidence of damage to the tibial post on each face

  20. Demographic Data Radiographic Analysis Methods • Age • Weight • Height • BMI • Length of implantation • Reason for revision • Femoral and tibial varus-valgus angle • Femoral component flexion-extension angle • Tibial posterior slope

  21. Rational Design Change • Determine stresses associated with box-post impingement in current design • Examine design alternatives intended to reduce stresses

  22. Model the Anterior Impingement

  23. Apply a Load in Hyperextension 445 N

  24. Finite Element Computer Model UHMWPE (elastic-plastic) Metal (rigid indenter)

  25. Polyethylene Stresses

  26. Polyethylene Deformation

  27. Polyethylene Deformation

  28. Polyethylene Deformation

  29. Original versus New Design 35%

  30. Reduction to Practice Rounded box to minimize bone resection

  31. The Importance of Retrieval Analysis Direct assessment of in vivo “real life” performance Early warning of unanticipated problems Justification for rational design changes

  32. Thanks for your attention

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