Leboeuf F, Sangeux M
Motion analysis service, Physical Medicine and Rehabilitation, Teaching Hospital of Nantes, France; School of Health & Society, The University of Salford, UK.
University Children's Hospital, Basel, Switzerland.
Gait Posture. 2023 Feb;100:243-246. doi: 10.1016/j.gaitpost.2022.12.013. Epub 2022 Dec 16.
The conventional gait model (CGM1) is extensively used for 3D clinical gait analysis. It uses lateral wand-mounted markers for the thigh and shank segments to avoid colinearity of the tracking markers. However, gait analysts may be tempted to use skin-mounted markers instead.
Does it matter if the lateral markers for the thigh and shank segments are mounted on wands or directly taped to the skin when using the CGM1?
Gait sessions from 147 and 73 patients equipped with wand-mounted and skin-mounted markers, respectively, were extracted from the database of a single clinical gait laboratory. The marker trajectories were reprocessed with the CGM1. The risk of marker colinearity was assessed from the planar angle constructed from the proximal joint center, the lateral joint marker and the lateral segmental marker (i.e. skin or wand). We assessed the effect of marker misplacement and soft-tissue artefact on kinematics.
The averaged planar angles calculated from static ranged from 10° to 30° and 7° to 21° for the skin-mounted thigh and shank markers respectively, while planar angles were always larger than 25° with wand-mounted markers. One cm misplacement of the thigh marker altered hip rotation by 10° if skin-mounted against 5° if wand-mounted. Soft tissue artefact led to 7.6° or 4.3° depending if it was skin- or wand-mounted, respectively.
Our analysis showed moderate risk of collinearity, increased effect of STA, and larger potential effect of marker misplacement with the use of skin- rather than wand-mounted markers.
传统步态模型（CGM1）广泛用于三维临床步态分析。它在大腿和小腿节段使用安装在横杆上的外侧标记物，以避免跟踪标记物共线。然而，步态分析师可能会倾向于使用直接贴在皮肤上的标记物。
在使用CGM1时，大腿和小腿节段的外侧标记物安装在横杆上还是直接贴在皮肤上有关系吗？
分别从一个临床步态实验室的数据库中提取了147例和73例配备了安装在横杆上和直接贴在皮肤上的标记物的患者的步态数据。使用CGM1对标记物轨迹进行重新处理。根据由近端关节中心、外侧关节标记物和外侧节段标记物（即皮肤或横杆）构成的平面角度评估标记物共线的风险。我们评估了标记物错位和软组织伪影对运动学的影响。
对于贴在皮肤上的大腿和小腿标记物，静态计算的平均平面角度分别为10°至30°和7°至21°，而对于安装在横杆上的标记物，平面角度始终大于25°。如果标记物贴在皮肤上，大腿标记物错位1厘米会使髋关节旋转改变10°，而如果安装在横杆上则为5°。软组织伪影分别导致7.6°或4.3°的变化，具体取决于标记物是贴在皮肤上还是安装在横杆上。
我们的分析表明，使用贴在皮肤上而非安装在横杆上的标记物时，共线风险适中，软组织伪影的影响增加，标记物错位的潜在影响更大。
