Selective Epiphysiodesis of the Anterior Distal Femoral Physis Alters Trochlear Morphology in a Rabbit Model

Background: Trochlear dysplasia is a leading contributor to patellofemoral instability, but the developmental role of the anterior distal femoral physis in shaping trochlear morphology remains poorly understood. Hypothesis: Selective closure of different portions of the anterior distal femoral physis would alter trochlear morphology in a predictable manner based on the region of growth arrest. Study Design: Controlled laboratory study. Methods: A total of 12 New Zealand White rabbits underwent unilateral selective epiphysiodesis of the anterior distal femoral physis at either the medial, central, or lateral region (n = 4 per group). Contralateral limbs served as internal controls. At 6 months postoperatively, gross, micro–computed tomography (µCT), and histological assessments were performed. µCT parameters including sulcus angle, trochlear depth, trochlear inclination, and facet symmetry were analyzed. A caliper was used to measure trochlear width as well as trochlear ridge height and length. The paired t test compared treated versus control limbs within each group. Results: Selective epiphysiodesis altered trochlear morphology in a region-specific pattern. Lateral epiphysiodesis resulted in a decreased proximal sulcus angle ( P = .005) and an increased lateral trochlear depth proximally ( P = .021), centrally ( P = .031), and distally ( P = .036), as measured on axial µCT. Central epiphysiodesis increased medial trochlear depth ( P = .009) and medial trochlear inclination ( P = .007), with greater facet symmetry ( P = .016). Medial epiphysiodesis reduced lateral trochlear depth ( P = .030) and lateral trochlear inclination ( P = .031), with an increased medial facet length ( P = .003). Direct caliper measurements showed an increased trochlear width ( P = .043) and increased medial trochlear ridge height ( P = .043) as a result of central epiphysiodesis. No cartilaginous changes were noted grossly or histologically. Conclusion: The anterior distal femoral physis significantly contributed to shaping the trochlear groove during skeletal growth. Targeted physeal closure altered trochlear morphology, supporting the potential for growth modulation strategies in managing early dysplastic changes. Lateral epiphysiodesis reduced the proximal sulcus angle and deepened the lateral groove. Central epiphysiodesis could be utilized to increase medial trochlear depth and symmetry between the medial and lateral trochlear facets. Clinical Relevance: The findings highlight the potential for early growth modulation strategies in skeletally immature patients at risk for trochlear dysplasia and patellofemoral instability. Understanding the growth contribution of the anterior distal femoral physis may inform the timing and nature of surgical or nonsurgical interventions in young patients.