Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA.
Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA; Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA.
Gait Posture. 2021 Oct;90:380-387. doi: 10.1016/j.gaitpost.2021.09.180. Epub 2021 Sep 20.
Clinical imaging often excludes the distal humerus, confounding definition of common whole-bone coordinate systems. While proximal anatomy coordinate systems exist, no simple method transforms them to whole-bone systems. Their influence on humeral kinematics is unknown.
How do humeral kinematics vary based on proximal and whole-bone coordinate systems, and can average rotation matrices accurately convert kinematics between them?
Three proximal coordinate systems were defined by the lesser and greater tuberosities (LT, GT), Crest of the greater tuberosity, and humeral shaft. Average rotation matrices derived from anatomic landmarks on cadaver humeri were generated between the proximal and whole-bone coordinate systems. Absolute angle of rotation was used to determine if anatomical variability within the cadaver population influenced the matrices. The matrices were applied to humerothoracic and glenohumeral motion (collected previously) and analyzed using the proximal coordinate systems, then expressed in the whole-bone system. RMSE was used to compare kinematics from the proximal and whole-bone systems.
A single average rotation matrix between a given proximal and whole-bone coordinate system achieved consistent error, regardless of landmarks. Elevation and plane of elevation had <2° mean error when proximal coordinate systems were transformed to whole-bone kinematics. Axial rotation had a mean 7° error, primarily due to variable humeral head retroversion. Absolute angles of rotation did not statistically differ between subgroups. The average rotation matrices were independent of sex, side, and motion.
Proximal humerus coordinate systems can accurately predict whole-bone kinematics, with most error concentrated in axial rotation due to anatomic twist along the bone. These results enhance interpretability and reproducibility in expressing humerothoracic and glenohumeral motion data between laboratories by providing a simple means to convert data between common coordinate systems. This is necessitated by the lack of distal humerus anatomy present in most clinical imaging.
临床影像学常排除肱骨远端，从而混淆了常见全骨坐标系的定义。虽然存在近端解剖坐标系，但没有简单的方法将其转换为全骨系统。它们对肱骨运动学的影响尚不清楚。
基于近端和全骨坐标系，肱骨运动学有何变化，平均旋转矩阵能否准确地在它们之间转换运动学？
通过小结节（LT）、小结节嵴和肱骨干来定义三个近端坐标系。从尸体肱骨上的解剖标志生成近端和全骨坐标系之间的平均旋转矩阵。应用解剖标志来确定尸体人群内的解剖变异性是否影响矩阵。将矩阵应用于肩胸和盂肱运动（先前收集），并使用近端坐标系进行分析，然后用全骨系统表示。使用均方根误差（RMSE）比较近端和全骨系统的运动学。
无论标志如何，特定近端和全骨坐标系之间的单个平均旋转矩阵都能达到一致的误差。当将近端坐标系转换为全骨运动学时，矢状面和冠状面的升高角度平均误差<2°。轴向旋转的平均误差为 7°，主要是由于肱骨头后倾的变化。旋转角度的绝对值在亚组之间没有统计学差异。平均旋转矩阵与性别、侧别和运动无关。
近端肱骨坐标系可以准确预测全骨运动学，大部分误差集中在轴向旋转上，这是由于骨骼的解剖扭转。这些结果通过提供一种简单的方法在常见坐标系之间转换数据，增强了在实验室之间表达肩胸和盂肱运动数据的可解释性和可重复性。这是由于大多数临床影像学中缺乏肱骨远端解剖结构所致。
