RESUMO
A 74-year-old man underwent total knee arthroplasty in 1996 and subsequent revision total knee arthroplasty for aseptic loosening in 2005. During revision, an all-polyethylene, 7-mm, second-generation, highly cross-linked ultra-high-molecular-weight polyethylene patellar component (Durasul; Zimmer, Warsaw, Indiana) was used. The patient recovered well, but he presented with severe acute pain after a popping feeling was detected during a game of golf in postoperative year 4. Radiographs demonstrated a fracture of the patellar component. At re-revision surgery, polyethylene fragments were encountered without visual evidence of wear. Appropriate rotational and axial alignment of the components was confirmed. Patellar revision was performed. To the authors' knowledge, this is the first report of an acute posttraumatic catastrophic fracture of a second-generation, highly cross-linked ultra-high-molecular-weight polyethylene patellar component. Although no malposition of the components was noted, abnormal tensile forces across the patellar component can be transmitted by altered patellofemoral kinematics. This combination could lead to a small surface crack that propagates deeper into the component with continued impaction and an eventual acute fracture of the entire component. The patellar component failed in a piecemeal fashion following acute trauma. Although many advantages exist to the enhancement of polyethylene patellar components, including the potential for improved wear characteristics, cross-linking has reduced resistance to crack initiation and propagation. Therefore, fracture risk should be considered when using second-generation, highly cross-linked ultra-high-molecular-weight polyethylene.