Lin Cheng-Chung, Chang Chia-Lin, Lu Ming, Lu Tung-Wu, Wu Ching-Ho
Department of Electrical Engineering, Fu Jen Catholic University, New Taipei City, Taiwan.
Institute of Veterinary Clinical Science, School of Veterinary Medicine, National Taiwan University, Taipei City, Taiwan.
BMC Vet Res. 2018 Dec 7;14(1):389. doi: 10.1186/s12917-018-1714-7.
Three-dimensional joint kinematics during canine locomotion are commonly measured using skin marker-based stereophotogrammetry technologies. However, marker-related errors caused by the displacement of the skin surface relative to the underlying bones (i.e., soft tissue artifacts, STA) may affect the accuracy of the measurements and obscure clinically relevant information. Few studies have assessed STA in canine limbs during kinematic analysis. The magnitudes and patterns of the STA and their influence on kinematic analysis remain unclear. Therefore, the current study aims to quantify the in vivo STA of skin markers on the canine thigh and crus during passive joint motion. The stifle joints of ten dogs were passively extended while the skin markers were measured using a motion capture system, and skeletal kinematics were determined using a CT-to-fluoroscopic image registration method.
The skin markers exhibited considerable STA relative to the underlying bones, with a peak amplitude of 27.4 mm for thigh markers and 28.7 mm for crus markers; however, the amplitudes and displacement directions at different attachment sites were inconsistent. The markers on the cranial thigh and lateral crus closer to the stifle joint had greater STA amplitudes in comparison to those of other markers. Most markers had STA with linear and quadratic patterns against the stifle flexion angles. These STA resulted in underestimated flexion angles but overestimated adduction and internal rotation when the stifle was flexed to greater than 90°.
Marker displacements relative to the underlying bones were prominent in the cranial aspect of the thigh and the proximal-lateral aspect of the crus. The calculated stifle kinematic variables were also affected by the STA. These findings can provide a reference for marker selection in canine motion analysis for similar motion tasks and clarify the relationship between STA patterns and stifle kinematics; the results may therefore contribute to the development of STA models and compensation techniques for canine motion analysis.
犬类运动过程中的三维关节运动学通常使用基于皮肤标记的立体摄影测量技术进行测量。然而，皮肤表面相对于深层骨骼的位移所导致的标记相关误差（即软组织伪影，STA）可能会影响测量的准确性，并掩盖临床相关信息。很少有研究在运动学分析中评估犬类肢体的STA。STA的大小和模式及其对运动学分析的影响仍不清楚。因此，本研究旨在量化犬类大腿和小腿在被动关节运动期间皮肤标记的体内STA。在使用运动捕捉系统测量皮肤标记的同时，对十只犬的 stifle 关节进行被动伸展，并使用CT到荧光透视图像配准方法确定骨骼运动学。
皮肤标记相对于深层骨骼表现出相当大的STA，大腿标记的峰值幅度为27.4毫米，小腿标记的峰值幅度为28.7毫米；然而，不同附着部位的幅度和位移方向并不一致。与其他标记相比，靠近stifle关节的大腿前部和小腿外侧的标记具有更大的STA幅度。大多数标记的STA与stifle屈曲角度呈线性和二次模式。当stifle屈曲大于90°时，这些STA导致屈曲角度被低估，但内收和内旋被高估。
相对于深层骨骼的标记位移在大腿前部和小腿近端外侧较为突出。计算出的stifle运动学变量也受到STA的影响。这些发现可为类似运动任务的犬类运动分析中的标记选择提供参考，并阐明STA模式与stifle运动学之间的关系；因此，这些结果可能有助于犬类运动分析的STA模型和补偿技术的发展。
