Morphological Improvement of the Epiphyseal Plate and Trochlea After Surgical Correction in Skeletally Immature Patients With Patellar Dislocation and Trochlear Dysplasia

Background: Studies have revealed abnormalities of the epiphyseal plate of the distal femur in patients with trochlear dysplasia, but it is unclear whether the epiphyseal plate could be remodeled after surgical correction of patellar dislocation.

Purpose: To investigate whether the morphology of the epiphyseal plate and trochlea could be improved after medial patellar retinaculum plasty in skeletally immature patients and to investigate the correlations between the morphology of the epiphyseal plate and trochlear dysplasia as well as clinical outcomes.

Study design: Cohort study; Level of evidence, 3.

Methods: Eligible skeletally immature patients were retrospectively enrolled: 48 with patellar dislocation who received medial patellar retinaculum plasty in the surgical group, 41 with patellar dislocation who received nonoperative treatment in the nonsurgical group, and 96 without patellofemoral joint disorders in the control group. Three-dimensional modeling techniques using computed tomography scans of the distal femur were utilized to display the epiphyseal plate and trochlea. The epiphyseal plate was evaluated using surface area, volume, and trochlea-epiphysis distance. The trochlea was evaluated using surface area, volume, Dejour classification, trochlear groove depth, lateral condylar height, medial condylar height, sulcus angle, and lateral trochlear inclination. Radiological and clinical evaluations were performed.

Results: When compared with the control group at baseline, the surgical group had a smaller surface area and volume of the medial epiphyseal plate (P < .001; P < .001, respectively), a shorter medial and lateral trochlea-epiphysis distance (P < .001; P < .001), and a larger surface area and volume of the lateral epiphyseal plate (P = .001; P = .007). At final follow-up, the surgical group demonstrated numerous significant increases-in surface area and volume of the medial epiphyseal plate (P < .001; P < .001), medial and lateral trochlea-epiphysis distance (P < .001; P < .001), surface area and volume of the proximal trochlear groove (P < .001; P < .001), trochlear groove depth (P < .001), lateral condylar height (P < .001), medial condylar height (P < .001), lateral trochlear inclination (P < .001), and proportion of normal + type A trochlea-whereas its sulcus angle (P < .001) was significantly decreased. The morphological parameters of the epiphyseal plate and trochlea in the nonsurgical group were not significantly improved, except for lateral condylar height (P < .001) and medial condylar height (P < .001). The surgical group had better radiological outcomes than the nonsurgical group, including tibial tuberosity-trochlear groove distance, patellar tilt angle, patellar congruence angle, lateral patellar angle, and lateral patellar translation, as well as better clinical outcomes. The surface area and volume of the medial epiphyseal plate and medial and the lateral trochlea-epiphysis distance were risk factors for trochlear dysplasia and were positively correlated with patient-reported outcome measures.

Conclusion: The morphology of the dysplastic epiphyseal plate and trochlea were significantly improved, as accompanied by better radiological and clinical outcomes after surgical correction before epiphyseal closure in skeletally immature patients with patellar dislocation. Furthermore, the morphology of the medial epiphyseal plate and trochlea-epiphysis distance were risk factors for trochlear dysplasia and correlated with clinical outcomes.