Patellar instability with recurrent dislocation due to patellofemoral dysplasia. Results after surgical treatment.

Twenty-one patients (25 knees) with recurrent dislocation of the patella due to patellofemoral dysplasia were treated with a combined distal and proximal realignment of the extensor mechanism of the knee. In addition to traditional medial transfer of the tibial tuberosity, lateral release, and medial joint capsule duplication, vastus medialis transposition and deepening of the intercondylar sulcus on the proximal joint surface of the femur were done. A follow-up ranging from 1-14 years (mean 6 years) found the results excellent or good in 22 knees, fair or poor in three. One redislocation occurred after trauma. There were two minor complications which had no effect on the end result. The use of computerized tomography over the patellofemoral joint to assess patellar subluxation and patellofemoral dysplasia is an important part of the diagnostic preoperative evaluation.