Lee S B, Kim K J, O'Driscoll S W, Morrey B F, An K N
Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
J Bone Joint Surg Am. 2000 Jun;82(6):849-57. doi: 10.2106/00004623-200006000-00012.
Both static and dynamic factors are responsible for glenohumeral joint stability. We hypothesized that dynamic factors could potentially operate throughout the entire range of glenohumeral motion, although capsuloligamentous restraints (a static factor) have been thought to be primarily responsible for stability in the end-range of motion. The purpose of this study was to quantitatively compare the dynamic glenohumeral joint stability in the end-range of motion (the position of anterior instability) with that in the mid-range by investigating the force components generated by the rotator cuff muscles.
Ten fresh-frozen shoulders from human cadavera were obtained, and all soft tissues except the rotator cuff were removed. The glenohumeral capsule was resected after the rotator cuff muscles had been released from the scapula. A specially designed frame positioned the humerus in 60 degrees of abduction and 45 degrees of extension with respect to the scapula. The compressive and shear components on the glenoid were measured before and after a constant force was applied individually to each muscle with the humerus in five different positions (from neutral to 90 degrees of external rotation). The dynamic stability index, a new biomechanical parameter reflecting these force components and the concavity-compression mechanism, was calculated. The higher the dynamic stability index, the greater the dynamic glenohumeral stability.
In the mid-range of motion, the supraspinatus and subscapularis provided higher dynamic stability indices than did the other muscles (p < 0.05). On the other hand, when the position of anterior instability was simulated in the end-range of motion, the subscapularis, infraspinatus, and teres minor provided significantly higher dynamic stability indices than did the supraspinatus (p < 0.005).
The rotator cuff provided substantial anterior dynamic stability to the glenohumeral joint in the end-range of motion as well as in the mid-range.
A glenohumeral joint with a lax capsule and ligaments might be stabilized dynamically in the end-range of motion if the glenoid concavity is maintained and the function of the external and internal rotators, which are efficient stabilizers in this position, is enhanced.
静态和动态因素均对盂肱关节的稳定性起作用。我们推测，尽管人们认为关节囊韧带约束（一种静态因素）在运动终末范围内对稳定性起主要作用，但动态因素可能在盂肱关节运动的整个范围内发挥作用。本研究的目的是通过研究肩袖肌群产生的力分量，定量比较运动终末范围（前向不稳定位置）与运动中间范围的盂肱关节动态稳定性。
获取10个新鲜冷冻的人体尸体肩部标本，去除除肩袖以外的所有软组织。在肩袖肌群从肩胛骨松解后，切除盂肱关节囊。一个特殊设计的框架将肱骨相对于肩胛骨置于外展60度和伸展45度的位置。在肱骨处于五个不同位置（从中立位到外旋90度）时，分别对每块肌肉施加恒定力之前和之后，测量关节盂上的压缩和剪切分量。计算动态稳定性指数，这是一个反映这些力分量和凹面压缩机制的新生物力学参数。动态稳定性指数越高，盂肱关节的动态稳定性越大。
在运动中间范围内，冈上肌和肩胛下肌提供的动态稳定性指数高于其他肌肉（p < 0.05）。另一方面，当在运动终末范围模拟前向不稳定位置时，肩胛下肌、冈下肌和小圆肌提供的动态稳定性指数显著高于冈上肌（p < 0.005）。
肩袖在运动终末范围以及运动中间范围为盂肱关节提供了显著的前向动态稳定性。
如果保持关节盂凹面并增强在此位置起有效稳定作用的外旋肌和内旋肌的功能，关节囊和韧带松弛的盂肱关节在运动终末范围可能会获得动态稳定。
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