Treatment of Femoral Lengthening-related Knee Stiffness With a Novel Quadricepsplasty

Background: Knee stiffness is common after femoral lengthening. Certain patients require a quadricepsplasty when therapy does not improve flexion. A small subset of such patients may also have obligate patellar dislocation with knee flexion due to contracture of the extensor mechanism. We describe our surgical approach for both clinical situations and our outcomes in a pediatric population. Methods: Six patients, 2 with obligate patellar dislocation, were reviewed (9% of our femoral lengthening population). Indications for surgery included persistent symptomatic restriction of flexion after at least 3 months of therapy or obligate lateral patellar dislocation with knee flexion. Knee range of motion and clinical strength were assessed. Four patients were available for gait analysis and concentric quadriceps strength testing by isokinetic dynamometer. Patient satisfaction was surveyed by questionnaire. Results: All patients had full flexion before lengthening. The mean length gained (by circular external fixation and/or intramedullary motorized nail) was 10.7 cm. The mean age at the time of quadricepsplasty was 16 years. The average active flexion preoperatively was only 48 degrees. Two patients with obligate patellar dislocation and relatively good knee flexion inflated the average preoperative knee flexion. Although both had knee flexion to 100 degrees, the patella dislocated with flexion beyond 30 degrees. At follow-up (mean, 6.2 y) active flexion averaged 120 degrees (P < 0.004). All patients had 5/5 clinical strength and no significant quadriceps lag. No patients had patellar instability postoperatively. Isokinetic dynamometer revealed an average weakness of 63% compared with the non-operative quadriceps. Gait analysis indicated patients had near-normal gait patterns. All patients were satisfied and would pursue the same treatment. Conclusions: Our quadricepsplasty can significantly increase knee flexion and treat obligate patellar dislocation in the setting of extension contracture after femoral lengthening when non-operative measures fail. Level of Evidence: Level IV.