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

ABSTRACT

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.