A new factor predicting excessive femoral anteversion in patients with recurrent patellar dislocation

PURPOSE: Determining a new imaging method on full-leg standing lower limb radiographs to predict excessive femoral anteversion in patients with patellar dislocation. METHODS: This study included 119 patients with patellar dislocation from January 2014 to January 2021. The femoral anteversion and tibial torsion were measured by CT scanning. The medial condylar angle was measured by the full-leg standing lower limb radiographs. Pearson correlation coefficient was used to evaluate the correlation between rotation parameters and medial condylar angle. RESULTS: Included patients were divided into DFO group and control group according to whether they received derotational femoral osteotomy (DFO) operation or not. DFO group had significantly higher femoral anteversion (29.8° ± 7.2° vs 23.1° ± 6.5°, P < 0.05), higher tibial torsion (28.6° ± 6.9° vs 24.7° ± 7.9°, P < 0.05), lower medial condylar angle (154.8° ± 4.7° vs 157.5° ± 6.7°, P < 0.05) than control group. Correlation analysis showed that the values of femoral anteversion were significantly correlated with medial condylar angle (r = -0.719, P < 0.001). CONCLUSION: This study showed that medial condylar angle had a negative correlation with excessive femoral anteversion on the full-leg standing lower limb radiographs. The medial condylar angle can be a good predictor of femoral anteversion and can be used to guide the performance of DFO to treat patellar dislocation in clinical practice.