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Rotator Cuff Disease


BACKGROUND

Incidence

Accounts for 1/3 of referrals to shoulder clinics

Anatomy of Supraspinatus

  • Bipennate muscle,

  • Origin, supraspinous fossa of scapula

  • Insertion, Greater tuberosity of humerusby a 2x1cm ‘footprint’

  •  Posteriorly confluent with tendon of infraspinatus

  •  Anteriorly to tendon is the rotator interval of capsule, strengthened by coracohumeral and sup. Glenohumeral ligts

  • Deep surface of tendon merges with superior capsule of shoulder joint, in direct contact with humeral head

  •  Deep surface of tendon has a poor blood supply

  • Superiorly is the coracoacromial arch- acromion, coracoacromial ligt.and acromioclavicular joint

  •  Subacromial bursa between arch and tendon

 

Aetiology

Several theories

·         Avascularity of tendon

  • There is an avascular area in the supraspinatus tendon just proximal to its insertion, corresponding to the area of degeneration and rupture.

  • Lindholm and Moseley, felt this was where there was an anastomosis between blood vessels from the bone and those from the muscle belly

  • Rathburn and McNab proposed that with the arm adducted and neutral, there is constant pressure of humeral head on the supraspinatus, ‘wringing’ the blood out of the tendon in the critical area. They maintain that this precedes and is not the result of degenerative changes

·         Mechanical wear

  • Neer felt this is a mechanical process secondary to progressive wear.

  • Found to be only the anterior aspect of the acromion involved with or without osteophytes from the AC joint

  • Bigliani has described 3 types of acromion:

 

  •   A cadaveric study of 140 shoulders that 73% of rotator cuff tears found were in type 3 hooked acromions

·         Trauma  = Macro or Micro trauma

 

Pathology of Impingement

·         Abrasion of the rotator cuff due to narrowing of the bony tunnel through which the tendon passes. 90% of the disease occurring in the anterior half of the final 3cm of the supraspinatus tendon

·         Associated changes

  • Degenerative changes in the Acromioclavicular joint, with inferior osteophytes

  • Morphological changes in the anterior aspect of the acromion (Bigliani)

 



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