The morphology of patella changed significantly after soft tissue correction for children with recurrent patella dislocation

BACKGROUND: Although morphological improvement of femoral trochlea has been investigated in children with patellar dislocation after surgery, whether the patellar shape changed under the same condition is still unknown. The purpose of the study was to investigate the changes of patellar morphology in transverse plane following surgical correction of recurrent patellar dislocation in children. METHODS: A total of 22 patients with a mean age of 9.9 years (7 to 12) were included. All had unilateral recurrent patellar dislocation. The knees with recurrent patellar dislocation were treated with medial patellar retinaculum plasty and defined as the affected side. The contralateral knees with no symptom of patellar instability were considered as the unaffected side. All patients were treated between October 2014 and August 2018. Axial CT (Computed Tomography) scans were undertaken in all patients to assess the patella morphological characteristics on a particular axial image preoperatively and at the final follow-up. RESULTS: There were not significant differences about patellar transverse diameter, thickness and Wiberg angle between affected side and unaffected side before surgery and at the last follow-up respectively (The mean follow-up period: 28.0 ± 3.3 months). However, before surgery, the Wiberg-index in the affected side (0.74 ± 0.06) was significantly different from that in the unaffected side (0.64 ± 0.04). At the last follow-up, the Wiberg-index in the affected side (0.67 ± 0.05) and the unaffected side (0.65 ± 0.04) were not significantly different. Also, in the affected side, the Wiberg-index at the last follow-up was significantly lower than that before surgery (P < 0.05). The Wiberg-index in the unaffected side was not significantly different before surgery and at the last follow-up. CONCLUSION: The patellar morphology can change significantly after surgical procedures in children with patellar recurrent dislocation whose epiphysis is not closed.