Zijie Xu1, Hua Zhang1, Minkang Guo1, Zhenxing Wen1, Jian Zhang1, Aiguo Zhou2. 1. Department of Orthopaedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China. 2. Department of Orthopaedics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China. zhouaiguo@hospital.cqmu.edu.cn.
Abstract
PURPOSE: To evaluate the clinical relevance of the newly identified malalignment sign in predicting excessive femoral anteversion in patients with patellar dislocations. METHODS: A total of 55 patients with patellar dislocation who underwent surgical treatment between 2016 and 2019 were included in this study. Femoral anteversion, tibial torsion, and the femorotibial index were measured via a CT scan. The malalignment sign on the knee MRI was defined as a malalignment between the lateral side of the intercondylar fossa of the femur and the lateral intercondylar eminence of the tibial plateau. RESULTS: A positive malalignment sign was observed in 36 of the 55 patients. Increased femoral anteversion was significantly correlated with the number of frames with a positive malalignment sign (r = 0.511, P < 0.001). The value of femoral anteversion was significantly greater in the group with a positive malalignment sign (P = 0.02). For a femoral anteversion value of 32°, the sensitivity and specificity of the malalignment sign reached the maximal level of 89.5% and 47.2%, respectively. CONCLUSION: Increased femoral anteversion correlated significantly with a positive malalignment sign on knee MRI. However, tibial torsion did not affect the malalignment sign. A positive malalignment sign is evidence for femoral derotation osteotomy. LEVEL OF EVIDENCE: Level IV.
PURPOSE: To evaluate the clinical relevance of the newly identified malalignment sign in predicting excessive femoral anteversion in patients with patellar dislocations. METHODS: A total of 55 patients with patellar dislocation who underwent surgical treatment between 2016 and 2019 were included in this study. Femoral anteversion, tibial torsion, and the femorotibial index were measured via a CT scan. The malalignment sign on the knee MRI was defined as a malalignment between the lateral side of the intercondylar fossa of the femur and the lateral intercondylar eminence of the tibial plateau. RESULTS: A positive malalignment sign was observed in 36 of the 55 patients. Increased femoral anteversion was significantly correlated with the number of frames with a positive malalignment sign (r = 0.511, P < 0.001). The value of femoral anteversion was significantly greater in the group with a positive malalignment sign (P = 0.02). For a femoral anteversion value of 32°, the sensitivity and specificity of the malalignment sign reached the maximal level of 89.5% and 47.2%, respectively. CONCLUSION: Increased femoral anteversion correlated significantly with a positive malalignment sign on knee MRI. However, tibial torsion did not affect the malalignment sign. A positive malalignment sign is evidence for femoral derotation osteotomy. LEVEL OF EVIDENCE: Level IV.
Authors: Elias Ammann; Rahel L Meier; Erich Rutz; Patrick Vavken; Kathrin Studer; Carlo Camathias Journal: Knee Surg Sports Traumatol Arthrosc Date: 2020-03-04 Impact factor: 4.342