Yu Jack, McGarry Michelle H, Lee Yeon-Soo, Duong Long V, Lee Thay Q
Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, 5901 E. 7th Street, Long Beach, CA 98022, USA.
J Shoulder Elbow Surg. 2005 Jan-Feb;14(1 Suppl S):65S-71S. doi: 10.1016/j.jse.2004.09.019.
We repaired full-thickness rotator cuff tears in human cadaveric shoulder specimens. The purpose of this study was to determine whether a repaired supraspinatus will result in a change in joint forces, contact pressures and area, and position of the humerus relative to the glenoid compared with the pathologic and simulated complete-tear specimens. Force couples exist in the coronal plane between the deltoid and the inferior portion of the rotator cuff and in the transverse plane between the anterior cuff (subscapularis) and posterior cuff (infraspinatus and teres minor). This has served as a model for shoulder and rotator cuff research. Our model differs from previous studies in that the pectoralis major and latissimus dorsi/teres major were included because they are important contributors to shoulder function. Muscle force simulation was performed through a clamp, cable, and pneumatic system for the tendons of the rotator cuff, pectoralis major, and teres major/latissimus dorsi. Each specimen was tested in its native state of a full-thickness supraspinatus tear in 10 degrees and 60 degrees of abduction with neutral humeral rotation. In each position there were 2 loading conditions: (1) all muscles loaded with 60 N and (2) deltoid loaded with 90 N and 60 N for all others (3:2 ratio between the deltoid and supraspinatus). Pathologic tear, repaired, and simulated complete-tear conditions were subjected to the same testing sequence. After repair, there was an increase in percent inferior force in the 10 degrees abduction, 60-N loaded condition ( P = .02). The increase in percent inferior force may represent greater concavity-compression and spacer effect, which are both important functions of the supraspinatus. Contact pressure decreased in both the pathologic and simulated complete-tear conditions at 10 degrees abduction with 90-N deltoid loading ( P = .01). A corresponding increase in area was observed at this position for the pathologic tear condition only ( P = .01). This could represent greater concavity-compression, indicating that strengthening may provide a biomechanical benefit.
我们在人类尸体肩部标本上修复了全层肩袖撕裂。本研究的目的是确定与病理状态和模拟完全撕裂标本相比，修复后的冈上肌是否会导致关节力、接触压力和面积以及肱骨相对于关节盂位置的变化。在冠状面，三角肌与肩袖下部之间存在力偶；在横断面，前肩袖（肩胛下肌）与后肩袖（冈下肌和小圆肌）之间存在力偶。这已成为肩部和肩袖研究的一个模型。我们的模型与以往研究的不同之处在于纳入了胸大肌和背阔肌/大圆肌，因为它们对肩部功能有重要作用。通过夹钳、缆线和气动系统对肩袖、胸大肌以及大圆肌/背阔肌的肌腱进行肌力模拟。每个标本在其全层冈上肌撕裂的原始状态下，于外展10度和60度且肱骨中立旋转时进行测试。在每个位置有两种加载条件：（1）所有肌肉加载60 N；（2）三角肌加载90 N，其他所有肌肉加载60 N（三角肌与冈上肌的比例为3:2）。病理撕裂、修复和模拟完全撕裂状态均接受相同的测试序列。修复后，在10度外展、60 N加载条件下，下向力百分比增加（P = 0.02）。下向力百分比的增加可能代表更大的凹面压缩和间隔效应，这两者都是冈上肌的重要功能。在10度外展、三角肌90 N加载的病理和模拟完全撕裂状态下，接触压力均降低（P = 0.01）。仅在该位置的病理撕裂状态下观察到面积相应增加（P = 0.01）。这可能代表更大的凹面压缩，表明强化可能带来生物力学益处。
