The role of negative intraarticular pressure and the long head of biceps tendon on passive stability of the glenohumeral joint
The relatively incongruent articular surfaces of the glenoid cavity and humeral head make the glenohumeral joint (GHJ) inherently unstable. Several static and dynamic tissues work together in order to provide stability. This study investigated the contribution of negative intra-articular pressure and the tendon of the long head of the biceps (LHB) to passive stability in the shoulder joint.
The joint capsule was most lax at 30 degrees and most tensioned at 90 degrees of GHJ abduction. When the integrity of the joint capsule was interrupted, translations in all directions increased – the greatest increase was observed in anteroposterior direction in 30 degrees of GHJ abduction. When the LHB tendon was loaded with 20N, all translations decreased, especially in anteroposterior and inferior direction in 30 degrees of GHJ abduction. In case of small translation loads, this effect was even more distinct.
Pathologic conditions that interrupt the integrity of the GHJ capsule, such as a full tear of a rotator cuff muscle, can lead to increased translations and may therefore cause instability unless compensated by the rotator cuff muscles and the LHB tendon. > From: Alexander et al., J Shoulder Elbow Surg 22 (2013) 94-101. All rights reserved to the Journal of Shoulder and Elbow Surgery Board of Trustees.
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