Patients have a wider stance following valgus high tibial osteotomy

Abstract

Tibial articular surface deforms by the bone defects and articular wear with progression of medial knee osteoarthritis (knee OA). It will affect the kinematics of knee joint and lower extremity under various loading conditions, however the detail of this mechanism has not been clarified enough. The purpose of this study was to investigate the effect of tibial articular surface deformity on the kinematics of lower extremity during level in some severities of medial knee OA. Methods: Subjects were 57 knees in 50 adults (18 males and 32 females, age: 56.6±19.2y.o.). Medial knee OA severity was graded by the Kellgren and Lowrence classification (grade-0: 8 knees,-I: 8 knees,-II: 15 knees,-III: 18 knees and-IV: 8 knees). The deformity of tibial articular surface was analyzed by their computed tomography-based three-dimensional (3D) bone model, and the tilt of articular surface was evaluated as the angle of articular surface relative to the long axis of tibia on the frontal plane. Level walking of the subject was measured by a motion capture system at a sampling rate of 250Hz (VICON, Vicon Motion Systems, Ltd, UK), and then the kinematics of femur and tibia relative to the ground during level walking was estimated by combining the motion capture data and the femorotibial bone models. Knee-joint kinematics was evaluated as tibial motion relative to femur. Additionally, stride length and walking velocity were assessed as walking performance. The differences in the parameter among knee OA severities were analyzed statistically by the Kruskal-Wallis test (alpha ¼ 5%). Results: Following several tendencies indicated with progression of knee OA: (1) The tibial articular surface tilted medially relative to the long axis of tibia (p<0.05); (2) The stride length and walking velocity decreased significantly (p<0.01); (3) The peak of knee flexion angle decreased (p<0.01), and the peak of knee varus angle increased (p<0.01); (4) The tibial and femoral long axes during stance phase tilted to the lateral and medial sides relative to the vertical axis of the ground, respectively (p<0.01); (5) The tilt of tibial articular surface relative to the ground demonstrated no significant difference among knee OA severities. Conclusions: The knee-joint line during the stance phase kept the constant tilt relative to ground with progression of knee OA. The deformity of tibial articular surface affected to the kinematics of tibia relative to the ground during the stance phase. The results of this study indicated that the femoral motion relative to tibia during the stance phase was mainly regulated by the deformity of tibial articular surface. Consequently, there was the possibility that the deformity of tibial articular surface became stronger than healthy condition by the imbalance of contact force and the increased shear force on the tibial articular surface under the loading condition. These findings may be helpful to improve the implant placement of total knee arthroplasty and to develop the orthosis for preventing the medial knee OA progress...