A Computed Tomography Study of the Association Between Increased Patellar Tilt Angle and Femoral Anteversion in 30 Patients with Recurrent Patellar Dislocation.

BACKGROUND Increased femoral anteversion (FA) has been demonstrated in patients with recurrent patellar dislocation (RPD). However, the effect of FA on the patellar tilt angle (PTA) in patients with RPD is unclear. The aim of this study was to compare the FA and PTA between patients with RPD and healthy controls and to investigate the relationship between FA and PTA. MATERIAL AND METHODS A total of 30 knees with RPD and 30 knees from healthy volunteers were evaluated with computed tomography (CT). The FA and PTA were measured and compared between the RPD and control groups. Correlations between the two parameters were assessed in the two groups. RESULTS The FA was 27.7 ± 6.80 for the RPD group compared with 17.3±9.0° for the control group (P=0.000), and the PTA was 29.0±7.1° for the RPD group compared with 14.8±8.4° for the control group (P=0.000). A positive correlation was found between these two parameters in the RPD group (r=0.464; P=0.010). Further analysis showed a significant correlation with a FA of ≥25° in the RPD group (r=0.709; P=0.001), but no correlation was found with the control group. CONCLUSIONS A significantly higher FA and PTA were found in patients with RPD compared with controls. An increased PTA and a FA ≥25° were significantly associated with RPD. A derotational femoral osteotomy may be indicated to correct patellar tilt in patients with RPD when femoral anteversion is ≥25°.