Association between Patellar Instability and Increased Supratrochanteric Torsional Malalignment

Recurrent patellar dislocation (RPD) is a common condition, particularly in adolescents, with several anatomic factors, such as increased femoral torsion, contributing to its development. Accurate assessment of these factors is essential for effective diagnosis and treatment planning.

To examine the correlation between femoral torsion and RPD and to measure the level of torsion using magnetic resonance imaging (MRI).

Cross-sectional study; Level of evidence, 3.

A total of 212 individuals were initially screened. Of these, 22 patients (31 femurs) who satisfied the inclusion criteria were included in the final analysis as the study group. The control group consisted of 28 patients (28 femurs) without a history of RPD. MRI measurements were conducted across 3 distinct axial sections. Supratrochanteric torsion (STT) value, infratrochanteric torsion (ITT) value, and femoral anteversion were analyzed utilizing T2-weighted turbo spin-echo sections. The distribution of the variables was determined using the Kolmogorov-Smirnov test. The independent-samples t test and chi-square test were used to analyze quantitative independent data. The Fisher exact test was used when the conditions appropriate for the chi-square test were not met.

The mean femoral anteversion was higher in the patellar dislocation group, with a statistically significant difference (20.1 ± 3.8 vs 11.5 ± 1.8; P = .0001). The mean STT was significantly greater in the patellar dislocation group (41.3 ± 7.6 vs 35.2 ± 3.1; P = .0002). The mean ITT values were comparable between the groups (22.7 ± 2.8 vs 23.7 ± 2.3; P = .14).

Our results indicate that increased femoral anteversion in RPD originates from the supratrochanteric region of the femur. Future large-scale studies, specifically focusing on the relationship between femoral anatomic variables and patellar instability, could yield significant insights into this matter.