Clinical application of dislocation sign on knee magnetic resonance imaging：a new predictor of excessive femoral anteversion in patients with patellar dislocation

Abstract:

Objective：To investigate whether the dislocation sign on knee magnetic resonance imaging（MRI） can be used to predict excessive femoral anteversion in patients with patellar dislocation. Methods：A retrospective analysis was performed on the clinical data of 35 patients（4 males and 31 females） with patellar dislocation who attended our hospital from January 2016 to July 2018. The mean age was 21.3 years. The femoral anteversion angle was 28.3°±8.3°. The tibial torsion angle was 29°±8.9°. The femorotibial index was -1.3±11.1. The dislocation sign on knee MRI was defined as malalignment between the lateral wall of intercondylar fossa of the femur and the lateral intercondylar eminence of the tibial plateau. The number of frames with dislocation sign was 1.49±1.25. Results：Dislocation sign was observed in 25 of the 35 patients. There was a significant difference in femoral anteversion angle between the patients with dislocation sign and those without dislocation sign（P<0.05）. The femoral anteversion angle was significantly correlated with the number of frames with dislocation sign on knee MRI（P<0.05）. Conclusion：Dislocation sign can be identified on knee MRI and can be a predictor of excessive femoral anteversion in patients with patellar dislocation. The femoral anteversion angle can be es－timated by the number of frames with dislocation sign.