[Endoprosthetic wear analysis using virtual CAD-based radiographs]

The articulating parts of an endoprosthetic joint are subjected to constant wear, which results in loss of material. In peri-implant tissue, the wear debris particles cause aseptic inflammation with osteolysis and aseptic loosening. Due to the associated bone resorption-which can be considerable-"particle disease" represents a significant challenge for orthopedic surgeons. Continuous improvements in the material properties of polyethylene during the past decades have resulted in reduced wear and longer implant survival times. To evaluate wear properties in polyethylene liners after total hip arthroplasty in vivo, different graphics-based, semiautomatic software packages were developed to measure femoral head penetration in radiographic image series. However, the reduced wear properties of the new materials rendered their precise analysis and evaluation more difficult, and no software was able to reproduce the accuracy of the complex and expensive radiostereometric analysis first described by Selvik in 1974, which is still viewed as the gold standard. The aim of this study is to describe the validation of a novel and accurate method to analyze polyethylene wear in vivo using virtual computer-aided detection/diagnosis (CAD)-based radiographic images. Furthermore, its use is presented based on the first 5‑year follow-up results of a multicenter approach evaluating the impact of vitamin E-blended polyethylene in cementless total hip replacement. Our data support the high accuracy of CAD-based virtual evaluation.