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Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria EBRA-FCA: A METHOD FOR MIGRATION MEASUREMENT OF.

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Presentation on theme: "Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria EBRA-FCA: A METHOD FOR MIGRATION MEASUREMENT OF."— Presentation transcript:

1 Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria EBRA-FCA: A METHOD FOR MIGRATION MEASUREMENT OF FEMORAL COMPONENTS OF THRs IN DIGITAL STANDARD RADIOGRAPHS PETER MAYRHOFER, revisited April 2012

2 EBRA-FCA (for Femoral Component) 2-dimensional method calibration by head diameter comparability algorithm also applicable to hip x-rays PARAMETERS FOR subsidence of the stem angle between bone axis and stem axis Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

3 FCA LANDMARKS min. 3 points on head contour 4 points defining stem axis greater and lesser trochanter prosthetic shoulder 8 points on femoral contour Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

4 FCA PARAMETERS subsidence of stem angle between stem and bone axes medial & lateral distances stem axis - bone contour Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

5 FCA GRAPHICS PROGRAM PRINTER EXCEL Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

6 FCA ACCURACY a b c Application of a comparability algorithm with respect to the parameters a, b and c leads to an accuracy for stem subsidence of +/- 1.5mm (95% CL) Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria J Bone Joint Surg Br Mar;81(2): Accuracy of EBRA-FCA in the measurement of migration of femoral components of total hip replacement. Einzel-Bild-Rontgen-Analyse-femoral component analysis. Biedermann R, Krismer M, Stockl B, Mayrhofer P, Ornstein E, Franzen H.

7 FCA ACCURACY Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria FCA detects stem subsidence > 1mm with a specificity of 100% and a sensitivity of 78%. This means, that stable implants will be recognized in any case. Migrating prostheses will be found out only in 78% cases at that early stage. Thus FCA underestimates migration.


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