Supraspinatus tear with retraction
There is an area of relative avascularity a cm proximal to the point of
insertion into the greater tuberosity. In addition, there is a relatively
avascular area in the biceps tendon. This has been described as a critical
zone. Therefore, attrition, chronic irritation, and inflammatory processes
could result in weakening of these structures, leading to complete tears.
Progressively, as the tendinous portion of the Rotator cuff becomes thin
or torn, the Rotators allow the deltoid to pull the humerus against the
under surface of the acromion, thereby leading to more impingement and
tearing. In very large and chronic tears, the tendon may be put at risk
and is often found deficient at the time of surgery.
Impingement syndrome has been classified into three stages:
Stage I: Oedema and haemorrhage
Stage II: Further inflammatory changes with fibrosis and thickening of
the biceps tendon
Stage III: Disease eventually evolves into complete thickness tears of
the rotator cuff.
Ashok Raghavan, Manipal Hospital, Bangalore