A Novel Trochlear Dysplasia Model in Immature Rats via Targeted Injury of the Anterior Distal Femoral Epiphysis

Background: Trochlear dysplasia is a critical risk factor for patellar instability, and existing animal models focus on indirect mechanical intervention and fail to replicate its pathological process. Purpose: To describe a novel trochlear dysplasia model in rats and investigate changes in external morphology and internal architecture of the trochlea in this model. Study Design: Controlled laboratory study. Methods: Twenty immature 4-week-old Sprague-Dawley rats were subjected to targeted injury of the anterior distal femoral epiphysis in the left knee, with the right knee used as the control group. All rats were evaluated by gross observation and micro–computed tomography. Macroscopic measurements included sulcus angle (SA), trochlear groove depth (TGD), trochlear width, medial condylar height, lateral condylar height, medial trochlear inclination (MTI), lateral trochlear inclination (LTI), and trochlear bump height. Trabecular microarchitectural parameters of the distal femoral epiphysis included bone mineral density (BMD), bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp). Results: The surgical group exhibited growth arrest at the anterior distal femoral epiphysis and 4 distinct types of trochlear dysplastic manifestations with a flat, shallow trochlea and bump deformity at the entrance of the trochlea, whereas the control group showed normally deepened trochlear grooves. Compared with the control group, the surgical group had significantly larger SA (136.13°± 7.32° vs 122.45°± 8.28°; P = .020) and smaller TGD (0.49 ± 0.15 mm vs 0.67 ± 0.10 mm; P = .033), MTI (17.15°± 7.96° vs 24.32°± 4.27°; P = .018), and LTI (26.72°± 4.72° vs 34.65°± 6.04°; P = .012). No significant differences were observed in BMD, BV/TV, Tb.N, Tb.Th, and Tb.Sp between the 2 groups. Conclusion: A novel trochlear dysplasia animal model similar to humans was established in immature rats via targeted injury of the anterior distal femoral epiphysis, which exhibited growth arrest at the anterior distal femoral epiphysis and key pathological features of human trochlear dysplasia. Clinical Relevance: The model is a potential platform for investigating the basic mechanisms of trochlear dysplasia and developing therapeutic treatments.