关节结构复杂，服役工况多种多样。下肢关节参与了人体大部分的日常活动，是运动系统的重要组成部分。下肢关节损伤种类多、发生风险高、恢复时间长，会对患者的生活造成严重影响。目前，仍有很多临床问题亟待解决，一些关节疾病及关节二次损伤的发生原因尚不明确，一些关节损伤在治疗方案的选择上仍存在争议。因此，对人体下肢关节的生物力学行为进行研究有着重要的意义，在骨科损伤预防、临床诊断和治疗等多个方面都具有重要的作用。

本文从力学角度出发，借助于生物力学试验及有限元模拟的方法，对人体踝关节Weber-C型骨折、膝关节假体周围骨折、髋臼后壁骨折等下肢关节损伤、以及修复过程中的关键力学问题展开了研究：

（1）踝关节Weber-C型骨折术后力学稳定性研究。针对联合三角韧带损伤的Weber-C型踝关节骨折，探究缝合锚修复三角韧带的治疗方法能否替代螺钉固定法。通过踝关节损伤模型外旋、外翻的生物力学试验以及相应有限元模型的运动分析，评估踝关节的术后力学稳定性发现：使用缝合锚修复三角韧带在外翻工况能够提供更坚固的稳定，但在外旋工况下，下胫腓处的分离要比螺钉固定法严重。分析了影响缝合锚修复三角韧带治疗效果的因素，发现：使用与韧带刚度相近的缝合锚线，将缝合锚固定在距骨的偏前位置会提高踝关节抵抗外旋的能力；当下胫腓处骨间膜损伤严重时，使用缝合锚修复三角韧带治疗的同时，需要对下胫腓处补充约束进行加固。

（2）全膝膝关节置换术后股骨远端假体周围骨折原因分析。重建膝关节及假体模型，借助有限元方法对站立、屈膝、行走典型工况下股骨远端假体周围应力和塑性应变情况进行分析，发现：假体边缘线区域是骨折发生的危险区域，行走工况造成的局部应力集中是诱发全膝关节置换后股骨远端发生由外侧下方至内侧上方骨折的重要原因。

（3）髋臼后壁骨折内固定的力学稳定性。针对髋臼骨折中，骨折块较大的后壁骨折情况，建立力学试验及有限元模拟的髋臼骨折损伤模型，对比使用不同内固定术的固定效果。试验与有限元模拟得到较为一致的结论：使用加压螺钉联合钢板固定且将钢板置于螺钉外侧的方案能提供更高的力学稳定性。

The structure of joint is complex and the working conditions are varied. The joints of lower limbs participate in most of daily activities and are an important part of the motor system. Lower limbs joint injury has multiple types, high risk and long recovery time, which will have a serious impact on patients’ life. At present, there are still many clinical problems to be solved. The causes of some joint diseases and secondary injuries are still unclear, and the choice of treatment options for some joint injuries is still controversial. For this reason, it is of great significance to study the biomechanical behavior of human joints, which plays an important role in the prevention,clinical diagnosis and treatment of orthopedic injuried.

From the mechanical point of view, by means of biomechanical test and finite element simulation, this paper studied some key mechanical problems in the injury and repair of lower limb joints, such as Weber-C fracture of ankle, periprosthetic fracture of knee, posterior wall fracture of acetabulum and so on.

(1) Postoperative mechanical stability of Weber-C fracture of ankle joint. In view of Weber-C ankle fracture combined with triangular ligament injury, to explore whether the treatment of repairing triangular ligament with suture anchor can replace screw fixation. Through the biomechanical test of external rotation and valgus of ankle injury model and the motion analysis of corresponding finite element model, the postoperative mechanical stability of ankle joint was evaluated. It was found that the use of suture anchors to strengthen the repair of triangular ligament valgus could provide stronger stability, but under external rotation, the separation of the lower tibia and fibula was more serious than that of screw fixation. The factors affecting the therapeutic effect of suture anchor in repairing triangular ligament were analyzed. It was found that using suture anchor whose mechanical properties were similar to ligament stiffness and fixing suture anchor in the anterior position of talus would improve the ability of ankle to resist external rotation. When the interosseous membrane of the lower tibia and fibula is seriously injured, it is necessary to reinforce the inferior tibia and fibula while using the suture anchor to repair the triangular ligament.

(2) Analysis of the causes of periprosthetic fracture of distal femur after total knee arthroplasty. The models of knee joint and prosthesis were reconstructed, and the stress and plastic strain around distal femoral prosthesis under typical working conditions of standing, knee flexion and walking were analyzed by finite element method. It was found that the marginal line of the prosthesis was a dangerous area for fracture, and the local stress concentration caused by walking was an important reason for the fracture of distal femur from lateral lower to medial upper after total knee arthroplasty.

(3) Mechanical stability of internal fixation of acetabular posterior wall fracture. The mechanical model and finite element model of acetabular posterior wall fracture were established. In view of the large posterior wall fracture of acetabular fracture, the fixation effects of different internal fixation were compared. The conclusion of the experiment is consistent with that of the finite element simulation. The scheme of using compression screw combined with steel plate fixation and placing the steel plate on the outside of the screw can provide higher mechanical stability.