Sex-Specific Adolescent Development of the Trochlea and Distal Femoral Physis: A 3D Shape Modeling Study.

BACKGROUND: Trochlear dysplasia is a primary risk factor for patellar instability and is associated with high recurrence rates, early arthritis, and poor return-to-sport outcomes. Surgical correction with trochleoplasty can improve tracking but carries risks in skeletally immature patients, including physeal damage and growth disturbance. PURPOSE: To inform safer surgical decision-making and refine current treatment strategies with a clearer understanding of how the trochlea and physis develop during adolescence is needed. STUDY DESIGN: Cross-sectional study; Level of evidence 3. METHODS: The authors retrospectively analyzed 261 nondysplastic knee magnetic resonance images from individuals aged 8 to 22 years. The authors trained a deep learning model to segment diaphyseal and epiphyseal femoral structures, and then constructed sex-specific statistical shape models of distal femoral shape and physis location. Regression analyses indicated a typical progression of femur shape with age. RESULTS: Between ages 13 and 19 years, both sexes demonstrated proximal migration of the physis and deepening of the trochlea, with greater lateral trochlear depth than medial trochlear depth. Across this age range, medial and lateral trochlear growth progressed at similar rates. After age 16, males demonstrated a significantly greater size-standardized lateral trochlear depth than females. CONCLUSION: These findings enhance understanding of sex-specific trochlear development and physeal positioning while demonstrating the utility of deep learning-based 3-dimensional modeling for characterizing knee growth.