No Growth Disturbance After Trochleoplasty for Recurrent Patellar Dislocation in Adolescents With Open Growth Plates.

BACKGROUND: Trochlear dysplasia is the most important risk factor for patellofemoral instability among adolescents; therefore, trochleoplasty to reshape the trochlear groove is the treatment of choice for patients with high-grade trochlear dysplasia. However, in the presence of open growth plates, there is a potential risk of injury to the distal femoral growth plate and subsequent growth disturbance. As such, most authors do not recommend trochleoplasty for skeletally immature patients. The effect of trochleoplasty on femoral growth when performed before closure of the distal femoral physis remains unclear.

HYPOTHESIS: For patients with open growth plates and an expected growth <2 years, trochleoplasty does not cause growth disturbance of the distal femur.

STUDY DESIGN: Case series; Level of evidence, 4.

METHODS: Eighteen consecutive adolescents (18 knees) with open physes and severe trochlear dysplasia underwent thin flap trochleoplasty. Pre- and postoperative radiographic examination included anteroposterior and lateral views to assess leg axis and patella alta. A preoperative radiograph of the left hand was performed to measure skeletal age. Magnetic resonance imaging was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove distance. Evaluation included pre- and postoperative physical examination with evaluation of leg length and leg axis, Kujala score, and Tegner activity score.

RESULTS: The median age at the time of operation was 12.6 years (range, 12.2-13.3 years) for girls and 14.5 years (14.0-15.4 years) for boys. The mean follow-up after operation was 2.3 years after surgery (range, 2.0-3.0 years). At follow-up for all patients, the growth plates of the knee were closed. Impairment of growth of the distal femur was found neither clinically nor radiographically. No recurrent dislocation occurred. The median Kujala score improved significantly from 67 (range, 54-75) preoperatively to 89.5 (range, 78-96) at follow-up ( P < .01). The median visual analog scale showed significant pre- to postoperative improvement from 5 (range, 3-7) to 1 (range, 0-3) ( P < .01). The activity level according to the Tegner activity score did not change significantly.

CONCLUSION: In this study, trochleoplasty as a treatment for patellofemoral instability of patients with open physes and an expected growth of not more than 2 years showed good clinical results without redislocation and with no growth disturbance. Therefore, for selected adolescent patients with high-grade trochlear dysplasia, trochleoplasty can be safely performed up to 2 years before the projected end of growth.