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Joints
The clinically important perihumeral space lies above the glenohumeral joint (GHJ) between the head of the humerus and an arch formed by the bony acromion, the thick coracoacromial ligament and coracoid process. This relatively tight compartment houses the subacromial bursa and the rotator cuff, particularly the vulnerable supraspinatus tendon. Excessive friction and pinching in this space render these structures prone to injury.
critical zone of relative ischaemia affecting rotator cuff about 1 cm medial to the attachment of the supraspinatus tendon, and this area is compromised during adduction and abduction of the arm due to pressure on the rotator cuff tendons from the head of the humerus. The so-called ‘impingement interval’ is the space between the under surface of the acromion and the superior aspect of the humeral head. This space is normally narrow (6–14 mm), especially when the arm is abducted.
Such factors are largely responsible for the many rotator cuff syndromes, including subacromial bursitis and lesions of the supraspinatus tendon and also bicipital tendonopathy.