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Loosening of the patellar component and extra-articular and transcutaneous migration after TKA.

Replacement of the patella during total knee arthroplasty (TKA) remains controversial. Despite some attempts to establish guidelines for this procedure, there is still no consensus in the literature. When the patella is replaced, the patient is subjected to certain complications, including loosening of the component. The loosened patellar component most commonly migrates to the intra-articular region of the knee. However, there have been a few reports of migration of the component to the extra-articular region, particularly when release of the lateral retinaculum and osteonecrosis of the patella are involved. The authors report a case of patellar component loosening and extra-articular and transcutaneous migration of the component 9 years after TKA. This report is unique because, during the primary procedure, no lateral release was performed and no patellar necrosis was evident on radiographs. The component was removed in the operating room and the wound cleaned and closed. Because of the probable slow migration of the component, there was no communication between the external environment and the joint at the time of surgery. There were no further complications after the wound healed. This case emphasizes the need for periodic radiographic follow-up after TKA.