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

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. a
FCA ACCURACY
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) b c
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.
Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

7. FCA ACCURACY Thus FCA underestimates migration.
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.
Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria