Brown Andrew J, Debski Richard E, Voycheck Carrie A, McMahon Patrick J
Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
Clin Orthop Relat Res. 2014 Aug;472(8):2397-403. doi: 10.1007/s11999-013-3419-3.
Using physical examination to make the diagnosis of shoulder instability can be difficult, because typical examination maneuvers are qualitative, difficult to standardize, and not reproducible. Measuring shoulder translation is especially difficult, which is a particular problem, because measuring it inaccurately may result in improper treatment of instability.
QUESTIONS/PURPOSES: The objective of this study was to use a magnetic motion tracking system to quantify the effects of external rotation of the abducted shoulder on a simulated simple translation test in healthy subjects. Specifically, we hypothesized that (1) increasing external rotation of the abducted shoulder would result in decreasing translation; (2) intraobserver repeatability would be less than 2 mm at all external rotation positions; and (3) mean side-to-side differences would be less than 2 mm at all external rotation positions.
The intraobserver repeatability and side-to-side differences of AP translation were quantified with a noninvasive magnetic motion tracking system and automated data analysis routine in nine healthy subjects at four positions of external rotation with the arm abducted. A shoulder positioning apparatus was used to maintain the desired arm position.
No differences in translations between the positions of external rotation were found (p = 0.48). Intraobserver repeatability was 1.1 mm (SD, 0.8 mm) and mean side-to-side differences were small: 2.7 mm (SD, 2.8 mm), 2.8 mm (SD, 1.8 mm), 2.5 mm (SD, 1.8 mm), and 4.0 mm (SD, 2.6 mm) at 0°, 20°, 40°, and 60° of external rotation, respectively.
The intraobserver repeatability was strong and the side-to-side differences in translation were small with the magnetic motion tracking system, which is encouraging for development of an improved quantitative test to assess shoulder translation for fast and low-cost diagnosis of shoulder instability.
Clinicians may not have to position the contralateral, normal, abducted shoulder in precisely the same position of external rotation as the injured shoulder while performing side-to-side comparisons.
通过体格检查来诊断肩关节不稳定可能具有挑战性，因为典型的检查手法具有主观性，难以标准化且无法重复。测量肩关节平移尤其困难，这是一个突出问题，因为测量不准确可能导致对不稳定的治疗不当。
问题/目的：本研究的目的是使用磁运动跟踪系统，量化外展肩关节外旋对健康受试者模拟简单平移试验的影响。具体而言，我们假设：（1）外展肩关节外旋增加会导致平移减少；（2）在所有外旋位置，观察者内重复性小于2毫米；（3）在所有外旋位置，左右侧平均差异小于2毫米。
使用无创磁运动跟踪系统和自动数据分析程序，对9名健康受试者在外展手臂的四个外旋位置进行前后位平移的观察者内重复性和左右侧差异进行量化。使用肩部定位装置维持所需的手臂位置。
未发现外旋位置之间的平移差异（p = 0.48）。观察者内重复性为1.1毫米（标准差，0.8毫米），左右侧平均差异较小：在外旋0°、20°、40°和60°时分别为2.7毫米（标准差，2.8毫米）、2.8毫米（标准差，1.8毫米）、2.5毫米（标准差，1.8毫米）和4.0毫米（标准差，2.6毫米）。
磁运动跟踪系统的观察者内重复性良好，平移的左右侧差异较小，这对于开发一种改进的定量测试以评估肩关节平移，用于快速、低成本诊断肩关节不稳定是令人鼓舞的。
临床医生在进行左右侧比较时，可能无需将对侧正常外展肩关节精确置于与受伤肩关节相同的外旋位置。
