MECHANISMS OF ROTATOR CUFF INJURY

MECHANISMS OF ROTATOR CUFF INJURY

The exact pathophysiology of rotator cuff injury, after exclusion of acute trauma, is still not fully understood. The current understanding is that rotator cuff degeneration is caused by a multifactorial pathogenesis, including both internal and external mechanisms.

Internal mechanisms

Those are mechanisms that originate from within the tendons in the form of degenerative processes, possibly age-related, that result in alterations in the tendon biology, morphology, vascularity and mechanical properties.

External mechanisms

External mechanisms include the well-known impingement syndromes, of which the subacromial impingement is the commonest. Subacromial impingement is defined as entrapment of the subacromial subdeltoid bursa and the supraspinatus tendon between the coraco-acromial arch and the greater tuberosity of the humerus. The main causes of this type of impingement include abnormal acromion configuration, osteoarthritis of the acromio-clavicular (AC) joint and narrowed subacromial space.

Another type of impingement syndromes is subcoracoid impingement; defined as entrapment of the subscapularis tendon in the coracohumeral interval (the space between the coracoid process and the anterior humerus). It is usually caused by abnormal coracoid configuration that may be congenital, traumatic or iatrogenic.

Less common types of impingement include secondary external impingement due to glenohumeral instability in the absence of outlet stenosis of the rotator cuff tendons, as well as internal impingement (intra-articular) due to compression of the articular surface of the tendons between the humeral head and glenoid.

Reference