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MBP 3970Z – 6 Week Project By: Patrick Lai Supervisor: Matt Teeter, Ph.D.c Medical Biophysics

Quantification of Third-Body Debris in Retrieved Polyethylene Orthopedic Components Using Micro-Computed Tomography. MBP 3970Z – 6 Week Project By: Patrick Lai Supervisor: Matt Teeter, Ph.D.c Medical Biophysics. Introduction.

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MBP 3970Z – 6 Week Project By: Patrick Lai Supervisor: Matt Teeter, Ph.D.c Medical Biophysics

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  1. Quantification of Third-Body Debris in Retrieved Polyethylene Orthopedic Components Using Micro-Computed Tomography MBP 3970Z – 6 Week Project By: Patrick Lai Supervisor: Matt Teeter, Ph.D.c Medical Biophysics

  2. Introduction • Total knee arthroplasty (TKA) and total hip arthroplasty (THA) are common methods of treatment for joint failure. • Approximately 60 000 hospitalizations in Canada due to TKA s and THAs • Increase of 101% from 10 years ago [1] • Average lifetime of implant: 10-15 years • Main reasons for failure of implant: • Osteolysis, Polyethylene wear, infection [2]

  3. Mechanics of TKA and THA

  4. Metallic Debris • Due to the mechanics and constant motion of implant • Metal debris and others can be embedded in the polyethylene liners

  5. Complication of Debris • Wears away bearing surface • Increases frictional forces • Osteolysis • Resorption of bone die to debris in joint capsule • Loosening of implant • Eventual failure

  6. Objectives • To quantify the amount of metal debris embedded in a polyethylene liner using micro CT • Develop a novel way of segmentation • Find possible errors and fixes for CT quantification

  7. Approach • Conduct segmentation of scans using micro CT images • Analyze data through ‘Paraview’ and ‘Microview’ software.

  8. Hypothesis • Using X-ray CT technology, third-party debris can be segmented from the polyethylene portions of a retrieved component

  9. Methods • Polyethylene components were surgically retrieved from failed TKR and THR • Specimens were pre-screened to have known third party debris • Scanned using Micro CT

  10. Surface rendering • Used Histogram to qualitatively set threshold levels • Microview takes threshold levels and creates isosurface • Using calibrated data from the scanner, the amount of voxels is converted into a volume • By making 2 surfaces: Polyethylene and Metal, the volume of the two are calculated.

  11. Results • No other benchmark to compare to • Therefore cannot quantitatively compare volume sizes • Visually inspect to qualitatively validate volume data • Volume data with visible artifacts are also rejected

  12. Histogram

  13. Surface reconstruction of Hip Poly

  14. Video

  15. Volume Data – Knee implants

  16. Results • Of the 11 specimens scanned: • 5 hip poly and 6 knee poly • 2 Hips polysand 2 Knee polys had anomalies

  17. Discussion- Examination of Artifacts – K722

  18. MIP – K722

  19. Surface rendering

  20. Discussion • X-ray CT can be a valid method of analyzing amount of metal debris in a retrieved poly • 7 of 11 polys measured without artifacts • The other 4 with artifacts are easily removed manually

  21. Future studies • The effect of outer artifacts on the volume measured inside • Methods of reducing artifacts

  22. Conclusion • Metal Debris can be quantified using micro CT method • Caution must be used to pre-screen images for artifacts before accepting results • Novel non-invasive way of determining volume

  23. Acknowledgements • Matt Teeter Ph.D.c • LyndsaySommervillePh.D.c

  24. Works Cited 1) Bohm, E., M. J. Dunbar, et al. (2009). "The Canadian Joint Replacement Registry—what have we learned?" ActaOrthopaedica81(1): 119-121. 2) Hayashi, A. (2009). "Modes of failure can predict outcomes after revision TKA " American Academt of Orthopaedic Surgeons News.

  25. Question Period

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