Lieber R L, Ljung B O, Fridén J
Department of Orthopedics, University of California, San Diego, USA.
Acta Orthop Scand. 1997 Jun;68(3):249-54. doi: 10.3109/17453679708996695.
Since the etiology of tennis elbow (lateral epicondylitis) is poorly understood, we studied the anatomical changes in the extensor carpl radialis brevis (ECRB) muscle during elbow joint rotation. Specifically, we measured ECRB sarcomere length, using an intraoperative laser diffraction procedure that measures muscle sarcomere length with an accuracy of +/- 0.05 micron. We found an unexpected biphasic response in ECRB sarcomere length as the elbow was rotated from full extension to full flexion. The initial sarcomere length of 3.49 microns, with the elbow extended, was gradually changed to 3.68 microns, 3.34 microns, 3.81 microns, and 3.45 microns with progressive elbow flexion. Based on the very nonlinear mechanical properties of skeletal muscle, this "double lengthening" of the ECRB during progressive flexion would impose intense eccentric contractions on the muscle itself. Given that eccentric contractions cause muscle injury and subsequent inflammation, these findings may provide insights into the etiology of lateral epicondylitis.
由于网球肘（外侧上髁炎）的病因尚不清楚，我们研究了肘关节旋转过程中桡侧腕短伸肌（ECRB）的解剖学变化。具体而言，我们采用术中激光衍射程序测量ECRB肌节长度，该程序测量肌肉肌节长度的精度为±0.05微米。我们发现，当肘关节从完全伸展旋转到完全屈曲时，ECRB肌节长度出现了意想不到的双相反应。肘关节伸展时，初始肌节长度为3.49微米，随着肘关节逐渐屈曲，该长度逐渐变为3.68微米、3.34微米、3.81微米和3.45微米。基于骨骼肌非常非线性的力学特性，在逐渐屈曲过程中ECRB的这种“双重延长”会对肌肉本身施加强烈的离心收缩。鉴于离心收缩会导致肌肉损伤和随后的炎症，这些发现可能为外侧上髁炎的病因提供见解。
