RESUMO
Objective To investigate the characteristics of knee kinematics and ground reaction force (GRF), as well as the stress state of cartilage and meniscus in the process of lateral incisions at different cutting angles under expected conditions. Methods Kinematics and GRF data of 14 subjects at 45°, 90° and 135° cutting angle respectively under expected conditions were collected. The knee joint reaction force was obtained through the inverse dynamics calculation of Visual 3D. Based on three-dimensional (3D) finite element model of the knee joint, the contact process at 3 lateral cutting angles was simulated. ResultsUnder expected conditions, there were significant differences in knee joint kinematics characteristics at 3 cutting angles during contact process(P＜0.001), and the knee flexion increased with the cutting angle increasing; the vertical GRF decreased significantly with the cutting angle increasing (P＜0.001), while the horizontal GRF showed the opposite trend; for 3 cutting angles, the peak contact stress of patellar cartilage and femoral cartilage was larger at 90° cutting angle, the peak principal stress at anterior cruciate ligament (ACL) contact point was also larger at 90° cutting angle, and the following was at 135° and 45° cutting angle, respectively; the peak contact stress of lateral femoral cartilage was larger than that of medial femoral cartilage at 3 cutting angles. Conclusions The risk of knee joint injury is higher at 90° cutting angle, and the stress state of knee joint at 135° cutting angles is better than that at 90° cutting angle, and the risk of knee joint injury does not increase with the increase of cutting angle under expected conditions.
RESUMO
Objective To discuss rationality of the three-link model used in analysis on interactive dynamics of deep squatting, and clarify the source of differences in calculation of joint torque by three-link model and Visual 3D. Methods Eight subjects were selected to obtain kinematic data of the squat motion through Vicon. The second Lagrangian equation was used to establish the three-link dynamic equation. The joint torque was calculated based on the Mathematica programming. The results were compared with the calculation results of lower limb chain segment model by Visual 3D, and the similarity between the two results was evaluated by the coefficient of complex correlation (CMC). Results The CMC of hip joint and knee joint from 8 subjects was larger than 0.85, and the CMC of ankle joint was between 0.50-0.85. The joint torque calculated by three-link dynamic equation and Visual 3D was highly similar in hip joint and knee joint, and there was only a moderate similarity in ankle joint. Conclusions The three-link model can be used in further analysis on interactive dynamics of deep squatting, but the influence of interactive moment caused by ground reaction force (external moment) on ankle torque should be considered.