EBRA-CUP A METHODS FOR MIGRATION MEASUREMENT OF ACETABULAR

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

EBRA INSTALLATIONS EUROPE • Belgium (1) OUTSIDE EUROPE • Austria (8) • San Francisco, US • Belgium (1) • Los Angeles, US • Denmark (5) • New Orleans, US • France (5) • Memphis Arlington, US • Germany (23) • New York, US • Greece (3) • Cleveland Ohio, US • Italy (2) • Ottawa, Canada • Netherlands (1) • Montreal, Canada • Norway (1) • Tokyo (2), Japan • Sweden (2) • Osaka, Japan • Switzerland (5) • Adelaide, Australia • United Kingdom (13) • Melbourne, Australia April 2012: 84 Installations EBRA has become an International Standard. • Shanghai, China Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EARLY MIGRATION > 1 mm IS PREDICTIVE FOR PROSTHETIC LOOSENING! J Bone Joint Surg Br. 1996 May; 78(3): 422 -26. Early migration predicts late aseptic failure of hip sockets. Krismer M, Stockl B, Fischer M, Bauer R, Mayrhofer P, Ogon M. J Bone Joint Surg Br. 1999 Mar; 81(2): 273 -80. The prediction of failure of the stem in THR by measurement of early migration using EBRA-FCA. Einzel-Bild-Roentgen-Analysefemoral component analysis. Krismer M, Biedermann R, Stockl B, Fischer M, Bauer R, Haid C. EBRA ENABLES QUALITY CONTROL FOR IMPLANT DESIGN & SURGICAL TECHNIQUE Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

mm Migration is only measurable in serial radiographs of the same patient whose position (exterior orientation) is never exactly the same. time EBRA requires at least 4 x-rays per series! Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA-CUP REQUIRES FULL SIZED AP PELVIS RADIOGRAPHS OF SIZE 430 x 350 mm digitized with film scanner or retrieved from PACS system including a scale for calibration! Resolution min. 75 dpi Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA-FCA ALSO ACCEPTS HIP RADIOGRAPHS NOT SHOWING THE WHOLE PELVIS. As the image is calibrated by the true head size, no scale is needed. Resolution min. 75 dpi Tip of stem must be visible! Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA • 1 standard x-ray per observation • no ball markers • retrospective studies RSA • 2 special x-rays per observation • markers required • prospective studies Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA-CUP PARAMETERS head & cup x-migration y-migration z-migration not possible y cup inclination & anteversion z x Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EXACT INTRINSIC ORIENTATION IS UNKNOWN IN STANDARD X-RAY Focus-film-distance and position of central beam have to be assessed approximatively. X-ray focus film plane principal point Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA - LANDMARKS film center approximative principal point Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

3 D-METHOD EBRA-CUP cup focus spatial parameter of migration reference plane reference line principal point film Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

ERRORS CAUSED BY CHANGES OF INTRINSIC ORIENTATION 1300 mm 900 mm Focus variation within cuboid 60 x 110 x 400 mm affects parameters of migration in a magnitude of only 0. 01 mm (experimental study based on 78 radiographs) Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

COMPENSATION OF ERRORS • by use of an approximative intrinsic orientation bound to pelvic contours (based on study of 78 random x-rays) • by use of variable reference planes passing through the x-ray focus Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EXTRINSIC ORIENTATION VARIES REMARKABLY Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

ERRORS CAUSED BY CHANGES OF EXTERIOR ORIENTATION Rotations of the pelvic bone cause remarkable errors up to 7 mm of simulated migration! Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

COMPENSATION OF ERRORS • by use of a comparability strategy which compares radiographs with respect to similar conditions at exposure • migration is measured only in pairs of comparable radiographs • overlapping trends are weighted and averaged Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA COMPARABILITY ALGORITHM non comparable x-ray migration raw data smoothed data time Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

ACCURACY TESTS • zero migration experiment (27 x-rays) • 33 pairs of x-rays taken within 1 month • comparison with RSA (T. Ilchman et al. ) J Arthroplasty. 1992 Jun; 7(2): 121 -27. Measurement accuracy in acetabular cup migration. A comparison of four radiologic methods versus roentgen stereophotogrammetric analysis. Ilchmann T, Franzen H, Mjoberg B, Wingstrand H. Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

EBRA - ACCURACY MIGRATION MEASUREMENT • medio-lateral mig: • cranial migration: 0. 8 mm (95% CI) 1. 0 mm (95% CI) ANGULAR MEASUREMENT • cup anteversion: • cup inclination: 3. 3° 2. 5° Department of Engineering Mathematics, Geometry and Computer Science, University of Innsbruck, Austria

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