Deformity analysis of the lower limb on the coronal plane in patients with rheumatoid arthritis and osteoarthritis.

OBJECTIVES: To evaluate joint orientation angles of the coronal plane in patients with rheumatoid arthritis (RA) in comparison with osteoarthritis (OA). METHODS: In total, 72 patients with RA (90 knees) and 76 patients with OA (90 knees) who underwent total knee arthroplasty were enrolled. The hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and joint line convergence angle (JLCA) were measured on preoperative long-leg radiographs in the standing position. Student's t-test was used to assess differences in radiographic data between patients with RA and OA. RESULTS: In knees with RA and OA, the mean HKA was -3.4 ± 9.4° and -10.6 ± 8.0°, the mean mLDFA was 86.6 ± 3.7° and 88.2 ± 2.7°, the mean mMPTA was 85.9 ± 4.0° and 84.3 ± 3.7°, and the mean JLCA was 2.7 ± 4.2° and 6.8 ± 4.1°. All parameters in the knees with RA were more valgus than those with OA. CONCLUSIONS: Knees with RA had a great variability in joint orientation angles on the coronal plane; the whole lower limb alignment and the femur, tibia, and joint were more valgus in knees with RA than with OA.

Medialization of the mechanical axis of the tibia is related to lateralization of the tibial tuberosity in knee osteoarthritis.

PURPOSE: To determine whether medialization of the proximal tibia due to a varus deformity is related to lateralization of the tibial tuberosity in varus knee osteoarthritis (OA). METHODS: A total of 120 knees that underwent osteotomies around the knee for varus knee OA were enrolled. Mechanical medial proximal tibial angle (mMPTA) was measured on radiographs. The angle between the mechanical and anatomical axes of the tibia (angle MA) and the distance between the centre of the tibial plateau and the anatomical axis (distance MA) were measured in the coronal plane on computed tomography images. The tibial tuberosity-posterior cruciate ligament (TT-PCL) distance, the distance between the midpoint of the tibial tuberosity and the centre of the tibial plateau (TT-centre distance), and the angle between the line through the midpoint of the tibial tuberosity and the centre of the tibial plateau and the anteroposterior axis (TT-centre angle) were measured in the axial plane. The correlations of these parameters were evaluated. RESULTS: mMPTA correlated negatively with angle MA (r = -0.37, P < 0.01) and distance MA (r = -0.55, P < 0.01). Angle MA and distance MA correlated with TT-PCL distance (r = 0.39, P < 0.01, r = 0.42, P < 0.01), TT-centre distance (r = 0.35, P < 0.01, r = 0.38, P < 0.01) and TT-centre angle (r = 0.36, P < 0.01, r = 0.36, P < 0.01). CONCLUSIONS: Medialization of the proximal tibia due to a varus deformity may induce lateralization of the tibial tuberosity.