Article ID: JNMS.2020_87-401
Background: Total knee arthroplasty (TKA) aims to correct the rotation as well as the alignment and the articulation of the osteoarthritic knee. In this study, we hypothesized that TKA affects hip rotational movement, in addition to improving knee kinematics. The objective was to evaluate the variation in lower extremity alignment and hip rotational range of motion (ROM) with TKA.
Methods: A total of 53 knees among 47 patients with primary varus knee osteoarthritis who were scheduled for primary TKA in our institute were enrolled. Hip rotational ROM was measured in the supine position with 90° flexion of the hip and knee before and 3 weeks after TKA. Variations in tibial axis alignment compared to femoral axis alignment by bone resections were also examined as changes in the joint lines of the distal femur and the proximal tibia using plain radiography and computed tomography.
Results: The average internal and sum of the internal and external hip rotational ROM increased significantly; however, the external hip rotational ROM was not significantly changed after TKA. The imaging findings also showed that the axis of the lower leg externally rotated 2.5° with a 4° external rotation of the distal femur and a 6.5° correction of the varus deformity.
Conclusion: TKA was proven to vary the neutral position of hip rotational movement and to increase hip rotational range of motion.