Gibb T D, Sidles J A, Harryman D T, McQuade K J, Matsen F A
Department of Orthopaedics, University of Washington, Seattle 98195.
Clin Orthop Relat Res. 1991 Jul(268):120-7.
Anesthetized shoulders are frequently stable against forces applied during drawer and sulcus tests, even though the shoulder muscles are inactive and do not contribute to stability. This passive stability is also evident in the glenohumeral joints of anatomic specimens. The translational laxity of anatomic specimen shoulders was measured, and it was demonstrated that this laxity was substantially increased when air was admitted into the capsule. Eight shoulders, aged 57-87 years, including six contralateral pairs, were analyzed using a six degrees-of-freedom force transducer and a six degrees-of-freedom spatial tracker. Capsules were vented by admitting air ad libitum through an 18-gauge needle. Venting reduced the force necessary to translate the humeral head with respect to the glenoid fossa by an average of 15.3 N (55%) for anterior forces, 10.8 N (43%) for posterior forces, and 19.0 N (57%) for inferior forces. It is likely that passive stability will also be diminished by a similar mechanism in patients with intact but excessively lax capsules. The principle of limited joint volume should be considered and tested when investigating glenohumeral stability.
尽管肩部肌肉处于非活动状态且对稳定性无贡献，但在抽屉试验和沟试验过程中施加外力时，麻醉后的肩部通常是稳定的。这种被动稳定性在解剖标本的盂肱关节中也很明显。对解剖标本肩部的平移松弛度进行了测量，结果表明，当向关节囊内注入空气时，这种松弛度会显著增加。使用六自由度力传感器和六自由度空间跟踪仪对8个年龄在57 - 87岁的肩部进行了分析，其中包括6对侧肩部。通过一根18号针头随意注入空气使关节囊排气。排气后，相对于肩胛盂平移肱骨头所需的力，向前的力平均减少了15.3 N（55%），向后的力减少了10.8 N（43%），向下的力减少了19.0 N（57%）。对于关节囊完整但过度松弛的患者，被动稳定性可能也会通过类似机制降低。在研究盂肱关节稳定性时，应考虑并测试关节容积有限的原理。
