Congenital dislocation of the patella

Abstract

Purpose Congenital dislocation of the patella is permanent and manually irreducible, and it manifests immediately after birth with flexion contracture of the knee, genu valgus, external tibial torsion and foot deformity. We retrospectively reviewed the results of operative treatment of seven knees in six patients with congenital dislocation of the patella. Methods The age of the six patients at diagnosis ranged from 8 days to 3.6 years, with an average of 1.3 years, and their age at the time of operation ranged from 0.6 to 3.9 years, with an average of 2.1 years. Serial casting and/or a brace was attempted before surgery in five of seven knees, leading to improvement in the flexion contracture of the knee. All knees were treated operatively in combination with lateral release, medial plication, V-Y lengthening of the quadriceps, medial transfer of the lateral patellar tendon and posterior release of the knee. Results Although these deformities were noticed at birth in all seven knees, diagnosis was delayed in three knees due to the low suspicion of the disease and invisible patellae on radiographs. Ultrasonography confirmed the diagnosis of dislocation. The patella was centered in the groove of the femoral condyle after surgery in all knees, but subluxation of the knee with flexion was observed in one knee in which the operation was performed at 3.9 years. Genu valgus and external tibial torsion improved after surgery in all knees. The operated knee was mobile in all cases, with less than 10° flexion contracture of the knee. Flexion contracture did not increase in any of the knees. Conclusion Congenital dislocation of the patella should be suspected in every patient with knee flexion contracture, genu valgus, external tibial torsion, foot deformity and delayed walking. Successful results were obtained when the operation was performed in younger children. Other procedures, such as the semitendinosus tenodesis or tendon transfer, might have to be combined to achieve better stability with flexion in older children.