Relationship Between Coronal Alignment and Rotational Profile of Lower Extremity in Patients With Knee Osteoarthritis

Background: We aimed at determining whether the coronal alignment of lower extremity was related to rotational geometry of distal femur, femoral anteversion, and tibial torsion in patients with knee osteoarthritis. Methods: A total of 422 lower extremities were divided into 3 groups according to the coronal alignment: valgus (n = 31), neutral (n = 78), and varus group (n = 313). Condylar twisting angle was measured to determine rotational geometry of distal femur as the angle between the clinical transepicondylar axis and the posterior condylar line. Femoral anteversion was assessed using the angle between a line intersecting the femoral neck and the posterior condylar line (pFeAV) and the angle between the same line and transepicondylar axis that is not affected by posterior condylar variations (tFeAV). Tibial torsion was evaluated by measuring the angle between the posterior condyles of the proximal tibia and the transmalleolar axis. Results: As the coronal alignment changed from varus to valgus, the condylar twisting angle increased (r = 0.253, P < .001; 6.6 degrees in varus, 7.4 degrees in neutral, and 10.2 degrees in valgus group). Although the pFeAV also increased (r = 0.145, P = .003), the tFeAV did not change significantly (P = .218). Mean tFeAV was 4.3 degrees in varus, 4.7 degrees in neutral, and 6.5 degrees in valgus group. In contrast, as the coronal alignment changed from varus to valgus, the external tibial torsion increased (r = 0.374, P < .001; 22.6 degrees in varus, 26.3 degrees in neutral, and 32.6 degrees in valgus group). Conclusion: The change patterns of the rotational profiles of the lower extremity according to the coronal alignment should be considered in order to obtain satisfactory rotational alignment after TKA. (C) 2018 Elsevier Inc. All rights reserved.