Oberhofer K, Mithraratne K, Stott N S, Anderson I A
The Bioengineering Institute, University of Auckland, Auckland, New Zealand.
J Biomech. 2009 Jan 5;42(1):77-81. doi: 10.1016/j.jbiomech.2008.10.007. Epub 2008 Dec 4.
Kinematic data from 3D gait analysis together with musculoskeletal modeling techniques allow the derivation of muscle-tendon lengths during walking. However, kinematic data are subject to soft tissue artifacts (STA), referring to skin marker displacements during movement. STA are known to significantly affect the computation of joint kinematics, and would therefore also have an effect on muscle-tendon lengths which are derived from the segmental positions. The present study aimed to introduce an analytical approach to calculate the error propagation from STA to modeled muscle-tendon lengths. Skin marker coordinates were assigned uncorrelated, isotropic error functions with given standard deviations accounting for STA. Two different musculoskeletal models were specified; one with the joints moving freely in all directions, and one with the joints constrained to rotation but no translation. Using reference kinematic data from two healthy boys (mean age 9y 5m), the propagation of STA to muscle-tendon lengths was quantified for semimembranosus, gastrocnemius and soleus. The resulting average SD ranged from 6% to 50% of the normalized muscle-tendon lengths during gait depending on the muscle, the STA magnitudes and the musculoskeletal model. These results highlight the potential impact STA has on the biomechanical analysis of modeled muscle-tendon lengths during walking, and suggest the need for caution in the clinical interpretation of muscle-tendon lengths derived from joint kinematics.
来自三维步态分析的运动学数据与肌肉骨骼建模技术相结合，能够得出步行过程中肌肉-肌腱的长度。然而，运动学数据容易受到软组织伪影（STA）的影响，软组织伪影是指运动过程中皮肤标记物的位移。已知STA会显著影响关节运动学的计算，因此也会对从节段位置推导得出的肌肉-肌腱长度产生影响。本研究旨在引入一种分析方法，以计算从STA到建模肌肉-肌腱长度的误差传播。为皮肤标记物坐标分配了具有给定标准差的不相关各向同性误差函数，以考虑STA。指定了两种不同的肌肉骨骼模型；一种模型中关节可在所有方向自由移动，另一种模型中关节被限制为只能旋转而不能平移。使用来自两名健康男孩（平均年龄9岁5个月）的参考运动学数据，对半膜肌、腓肠肌和比目鱼肌的STA到肌肉-肌腱长度的传播进行了量化。根据肌肉、STA大小和肌肉骨骼模型的不同，步态期间所得的平均标准差范围为标准化肌肉-肌腱长度的6%至50%。这些结果突出了STA对步行过程中建模肌肉-肌腱长度生物力学分析的潜在影响，并表明在临床解释从关节运动学得出的肌肉-肌腱长度时需要谨慎。
