Fiorentino Niccolo M, Atkins Penny R, Kutschke Michael J, Goebel Justine M, Foreman K Bo, Anderson Andrew E
Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108, USA.
Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108, USA; Department of Bioengineering, University of Utah, 36 S. Wasatch Drive, Room 3100, Salt Lake City, UT 84112, USA.
Gait Posture. 2017 Jun;55:184-190. doi: 10.1016/j.gaitpost.2017.03.033. Epub 2017 Mar 31.
Soft tissue movement between reflective skin markers and underlying bone induces errors in gait analysis. These errors are known as soft tissue artifact (STA). Prior studies have not examined how STA affects hip joint angles and range of motion (ROM) during dynamic activities. Herein, we: 1) measured STA of skin markers on the pelvis and thigh during walking, hip abduction and hip rotation, 2) quantified errors in tracking the thigh, pelvis and hip joint angles/ROM, and 3) determined whether model constraints on hip joint degrees of freedom mitigated errors. Eleven asymptomatic young adults were imaged simultaneously with retroreflective skin markers (SM) and dual fluoroscopy (DF), an X-ray technique with sub-millimeter and sub-degree accuracy. STA, defined as the range of SM positions in the DF-measured bone anatomical frame, varied based on marker location, activity and subject. Considering all skin markers and activities, mean STA ranged from 0.3cm to 5.4cm. STA caused the hip joint angle tracked with SM to be 1.9° more extended, 0.6° more adducted, and 5.8° more internally rotated than the hip tracked with DF. ROM was reduced for SM measurements relative to DF, with the largest difference of 21.8° about the internal-external axis during hip rotation. Constraining the model did not consistently reduce angle errors. Our results indicate STA causes substantial errors, particularly for markers tracking the femur and during hip internal-external rotation. This study establishes the need for future research to develop methods minimizing STA of markers on the thigh and pelvis.
反射性皮肤标记物与深层骨骼之间的软组织运动在步态分析中会引发误差。这些误差被称为软组织伪影（STA）。先前的研究尚未考察STA在动态活动期间如何影响髋关节角度和活动范围（ROM）。在此，我们：1）测量了步行、髋关节外展和髋关节旋转过程中骨盆和大腿上皮肤标记物的STA，2）量化了跟踪大腿、骨盆和髋关节角度/ROM时的误差，3）确定了对髋关节自由度的模型约束是否能减轻误差。11名无症状的年轻成年人同时使用反光皮肤标记物（SM）和双荧光透视（DF，一种具有亚毫米和亚度精度的X射线技术）进行成像。STA定义为DF测量的骨骼解剖框架中SM位置的范围，其因标记物位置、活动和受试者而异。综合所有皮肤标记物和活动来看，平均STA范围为0.3厘米至5.4厘米。与DF跟踪的髋关节相比，STA导致SM跟踪的髋关节角度伸展增加1.9°、内收增加0.6°、内旋增加5.8°。相对于DF测量，SM测量的ROM有所减小，在髋关节旋转期间，内外轴方向的最大差异为21.8°。对模型进行约束并不能始终减少角度误差。我们的结果表明，STA会导致显著误差，特别是对于跟踪股骨的标记物以及在髋关节内外旋转期间。本研究表明未来有必要开展研究以开发方法来最小化大腿和骨盆上标记物的STA。
