2.  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]

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

6.  Wears away bearing surface › Increases frictional forces  Osteolysis › Resorption of bone die to debris in joint capsule › Loosening of implant  Eventual failure

7.  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

8.  Conduct segmentation of scans using micro CT images  Analyze data through ‘Paraview’ and ‘Microview’ software.

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

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

11.  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.

13.  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

19. Specimen IRAL Number Volume at Threshold 250 (mm^3) Volume at Threshold 10000 (mm^3)Comments K22513288.4460.196 K29313652.7911.655 K39415866.7340 Showed no metal, but non-zero metal in MIP K68210731.8010.537 K72021051.4260.405 K72220734.746101.496Outer artifact

20.  Of the 11 specimens scanned:  5 hip poly and 6 knee poly  2 Hips polys and 2 Knee polys had anomalies

21. Specimen IRAL Number Volume at Threshold 250 (mm^3) Volume at Threshold 10000 (mm^3)Comments K22513288.4460.196 K29313652.7911.655 K39415866.7340 Showed no metal, but non-zero metal in MIP K68210731.8010.537 K72021051.4260.405 K72220734.746101.496Outer artifact

24.  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

25.  The effect of outer artifacts on the volume measured inside  Methods of reducing artifacts

26.  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

27.  Matt Teeter Ph.D.c  Lyndsay Sommerville Ph.D.c

28. 1) Bohm, E., M. J. Dunbar, et al. (2009). "The Canadian Joint Replacement Registry— what have we learned?" Acta Orthopaedica 81 (1): 119-121. 2) Hayashi, A. (2009). "Modes of failure can predict outcomes after revision TKA " American Academt of Orthopaedic Surgeons News.

29. Question Period