Papachristou George
2nd Department of Orthopaedics, National and Kapodistrian University, St Olga Hospital, N. Ionia, Athens, Greece.
Arch Orthop Trauma Surg. 2004 Jun;124(5):288-97. doi: 10.1007/s00402-004-0657-6. Epub 2004 Apr 2.
The treatment of knee osteoarthrosis represents a difficult task. Osteotomy is one of the treatment regimes which, in earlier times, was the only surgical procedure giving reliable mid-term results. The improvement was attributed either to the changing of the acting forces or to the so-called biological factor. The use of a photoelastic model allows the observation of the direction of the significant contact and internal stresses at every point in a single plane.
In the present study, we investigated the stress-strain situation of the knee joints in models made from 1 cm thick Araldite plates. These models reproduce tracings from anteroposterior X-ray views of monopodal loading of human knee joints. The models represent: normal knee joints, normal varus or valgus knee joint, knee joints suffering osteoarthrosis in varus or valgus, and knee joints suffering osteoarthrosis, following corrective osteotomies. The models were first loaded along the longitudinal axis with the leg in full extension, with 70 kg (body weight) and then with 140 kg, representing double the normal body weight.
The application of longitudinal force on a normal knee joint, in full extension, results in symmetrical arrangement of trajectories in the condyles. Loading of the leg in varus or valgus produces shifting of stresses towards the inclination side. Increased contact stresses are always greater in the tibial condyles. The concentration of strain is directed towards the cortices of the loaded area. In a knee joint with osteoarthrosis, deviation of the trajectories in the condyles towards the inclination of the leg axis is observed. Also, increased contact stresses appear in the articular surfaces, on the inclination side. Isoclinics have meeting points on the loaded cortices. Supracondylar femoral osteotomy, or high tibial osteotomy, restores the axis of the leg, redistributes internal stresses (strain) in the condyles, corrects the trajectorial lines, and redistributes contact stresses in the articular surfaces towards the normal values.
Correction of the femorotibial axis results in redistribution of the isochromatics, isoclinics, trajectorial lines and contact stresses. The values of the above parameters are corrected and remain closer to these of the normal knee, but in no case does the correction of all the above factors attain normal values. The change of direction of the main stresses following osteotomies towards those of the normal knee probably represents the biomechanical explanation of the way the osteotomy relieves pain and improves function.
膝关节骨关节炎的治疗是一项艰巨的任务。截骨术是治疗方案之一，在早期，它是唯一能给出可靠中期效果的外科手术。病情的改善要么归因于作用力的改变，要么归因于所谓的生物学因素。使用光弹性模型可以观察单个平面内每个点的显著接触方向和内部应力。
在本研究中，我们研究了由1厘米厚的环氧树脂板制成的模型中膝关节的应力应变情况。这些模型再现了人体膝关节单足负重前后位X线片的影像。这些模型代表：正常膝关节、正常内翻或外翻膝关节、内翻或外翻的骨关节炎膝关节以及截骨矫正后的骨关节炎膝关节。首先让腿部完全伸直，沿纵轴施加70千克（体重）的负荷，然后施加140千克的负荷，相当于正常体重的两倍。
在完全伸直的正常膝关节上施加纵向力，会导致髁部轨迹呈对称分布。腿部内翻或外翻负重会使应力向倾斜侧转移。胫骨髁部的接触应力增加总是更大。应变集中指向负重区域的皮质。在患有骨关节炎的膝关节中，观察到髁部轨迹向腿轴倾斜方向偏移。此外，在倾斜侧的关节表面也会出现接触应力增加。等倾线在负重皮质上有交汇点。股骨髁上截骨术或高位胫骨截骨术可恢复腿部轴线，重新分布髁部的内部应力（应变），校正轨迹线，并使关节表面的接触应力重新分布至接近正常值。
股骨 - 胫骨轴线的矫正会导致等色线、等倾线、轨迹线和接触应力的重新分布。上述参数的值得到校正，且更接近正常膝关节的值，但在任何情况下，对上述所有因素的校正都不会达到正常值。截骨术后主应力方向向正常膝关节的方向改变，这可能代表了截骨术缓解疼痛和改善功能方式的生物力学解释。
