Posttraumatic chronic patellar dislocation treated by distal femoral osteotomy and medial patellofemoral ligament reconstruction.

Chronic patellar dislocation is a rare condition where the patella remains dislocated throughout knee range of motion during flexion and extension. In adults, the delayed presentation of this condition is often due to symptoms caused by the onset of severe secondary osteoarthritis. To the authors' knowledge, all of the cases reported in the literature have been treated by patellofemoral or total knee replacements depending on patient age and the extent of the arthritis. This article describes a rare case of a 22-year-old woman who sustained a traumatic chronic patellar dislocation for 5 months. Clinical examination revealed a valgus deformity of the left leg secondary to childhood injury and that the patella lay lateral to the lateral femoral condyle throughout flexion and extension. Radiographs of the knee revealed patellar dislocation. Long-leg radiographs of the left leg showed an anatomic tibiofemoral angle of 17° valgus. The anatomical (74°) and mechanical (80°) lateral distal femoral angles were abnormal, whereas the medial proximal tibial angle (87°) was normal, confirming that the valgus deformity was due to the abnormal distal femur. The authors performed a distal femoral osteotomy to correct the valgus deformity. Medial patellofemoral ligament reconstruction using a hamstring autograft was performed to stabilize the patella.