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Wear remains an important cause of failure in knee replacement. Of the current methods of early performance assessment or prediction, simulators have been un-physiological, single X-ray film analyses remain limited by accuracy and retrieval and survival methods have a prohibitive time scale. An accurate method is needed to allow a timely assessment of polyethylene component wear in vivo, when a new design is introduced, in order to predict likely outcome. We present a new method for measuring wear in vivo that we believe will allow this prediction of long-term wear. X-ray film pairs were taken of implanted prosthetic metal components. When the X-ray system was calibrated, projections of the appropriate Computer Aided Design (CAD) model could be matched to the shapes on the scanned X-ray films to find component positions. Interpenetration of the metal femoral component into the polyethylene component could then be established and represents our estimate of "wear". This method was used to measure in vivo prosthesis wear to an accuracy of 0.11 mm.

Original publication




Journal article


Journal of biomechanics

Publication Date





315 - 322


OOEC/Nuffield Department of Orthopaedic Surgery, University of Oxford, Nuffield Orthopaedic Centre, Headington, Oxford OX3 7LD, UK.


Knee Joint, Humans, Prosthesis Failure, Biocompatible Materials, Radiographic Image Interpretation, Computer-Assisted, Imaging, Three-Dimensional, Photogrammetry, Arthroplasty, Replacement, Knee, Sensitivity and Specificity, Reproducibility of Results, Equipment Failure Analysis, Materials Testing, Knee Prosthesis, Biomechanics, Computer-Aided Design