Heegaard J, Leyvraz P F, Curnier A, Rakotomanana L, Huiskes R
Hôpital Orthopédique de la Suisse Romande, Lausanne, Switzerland.
J Biomech. 1995 Nov;28(11):1265-79. doi: 10.1016/0021-9290(95)00059-q.
The fundamental objectives of patello-femoral joint biomechanics include the determination of its kinematics and of its dynamics, as a function of given control parameters like knee flexion or applied muscle forces. On the one hand, patellar tracking provides quantitative information about the joint's stability under given loading conditions, whereas patellar force analyses can typically indicate pathological stress distributions associated for instance with abnormal tracking. The determination of this information becomes especially relevant when facing the problem of evaluating surgical procedures in terms of standard (i.e. non-pathological) knee functionality. Classical examples of such procedures include total knee replacement (TKR) and elevation of the tibial tubercle (Maquet's procedure). Following this perspective, the current study was oriented toward an accurate and reliable determination of the human patella biomechanics during passive knee flexion. To this end, a comprehensive three-dimensional computer model, based on the finite element method, was developed for analyzing articular biomechanics. Unlike previously published studies on patello-femoral biomechanics, this model simultaneously computed the joint's kinematics, associated tendinous and ligamentous forces, articular contact pressures and stresses occurring in the joint during its motion. The components constituting the joint (i.e. bone, cartilage, tendons) were modeled using objective forms of non-linear elastic materials laws. A unilateral contact law allowing for large slip between the patella and the femur was implemented using an augmented Lagrangian formulation. Patellar kinematics computed for two knee specimens were close to equivalent experimental ones (average deviations below 0.5 degrees for the rotations and below 0.5 mm for the translations) and provided validation of the model on a specimen by specimen basis. The ratio between the quadriceps pulling force and the patellar tendon force was less than unity throughout the considered knee flexion range (30-150 degrees), with a minimum near 90 degrees of flexion for both specimens. The contact patterns evolved from the distal part of the retropatellar articular surface to the proximal pole during progressive flexion. The lateral facet bore more pressure than the medial one, with corresponding higher stresses (hydrostatic) in the lateral compartment of the patella. The forces acting on the patella were part of the problem unknowns, thus leading to more realistic loadings for the stress analysis, which was especially important when considering the wide range of variations of the contact pressure acting on the patella during knee flexion.
髌股关节生物力学的基本目标包括确定其运动学和动力学，这是给定控制参数（如膝关节屈曲或施加的肌肉力量）的函数。一方面，髌骨轨迹提供了关于关节在给定负荷条件下稳定性的定量信息，而髌骨力分析通常可以表明例如与异常轨迹相关的病理应力分布。当面临根据标准（即非病理）膝关节功能评估手术程序的问题时，确定这些信息变得尤为重要。此类手术的经典例子包括全膝关节置换术（TKR）和胫骨结节抬高术（马凯特手术）。从这个角度来看，当前的研究旨在准确可靠地确定被动膝关节屈曲过程中的人体髌骨生物力学。为此，基于有限元方法开发了一个全面的三维计算机模型，用于分析关节生物力学。与先前发表的关于髌股生物力学的研究不同，该模型同时计算了关节的运动学、相关的肌腱和韧带力、关节接触压力以及关节运动过程中出现的应力。构成关节的组件（即骨骼、软骨、肌腱）使用非线性弹性材料定律的客观形式进行建模。使用增强拉格朗日公式实现了允许髌骨和股骨之间大滑动的单侧接触定律。为两个膝关节标本计算的髌骨运动学与等效的实验结果接近（旋转平均偏差低于0.5度，平移平均偏差低于0.5毫米），并在逐个标本的基础上对模型进行了验证。在整个考虑的膝关节屈曲范围（30 - 150度）内，股四头肌拉力与髌腱力的比值小于1，两个标本在屈曲接近90度时比值最小。在逐渐屈曲过程中，接触模式从髌后关节面的远端部分向近端极演变。外侧小面承受的压力比内侧小面大，髌骨外侧间室相应地有更高的应力（静水压力）。作用在髌骨上的力是问题的未知量之一，因此在应力分析中导致更现实的载荷，这在考虑膝关节屈曲过程中作用在髌骨上的接触压力的广泛变化范围时尤为重要。
