Cuff fiber failure commonly results from the sudden application of eccentric loads, for example when the muscle attempts to resist a downward force on the arm
while the cuff seems to be better able to tolerate concentric loads, for example in a controlled lift away from the side.
An anatomic factor predisposing to deep surface failure of the cuff insertion is internal abutment, where the corner of the glenoid contacts the deep aspect of the cuff at its tuberosity insertion
This is most likely to be a problem for throwers who have stretched out their anterior capsule, allowing increased external rotation.
It is apparent that the most common form of cuff fiber failure, that which occurs on the articular surface of the cuff tendon, cannot be attributed to scuffing of the bursal surface by the acromion: so-called subacromial ‘impingement.’ In fact, the cuff insertion is well under the acromion at relatively small angles of elevation where it is protected from contact with the coracoacromial arch. Current evidence indicates that the most rotator cuff tears arise from tension overload and age-related attrition, rather than 'impingement'.
Readers might be interested in a recent review of the literature regarding the diagnosis of "impingement syndrome".
It is apparent that the most common form of cuff fiber failure, that which occurs on the articular surface of the cuff tendon, cannot be attributed to scuffing of the bursal surface by the acromion: so-called subacromial ‘impingement.’ In fact, the cuff insertion is well under the acromion at relatively small angles of elevation where it is protected from contact with the coracoacromial arch. Current evidence indicates that the most rotator cuff tears arise from tension overload and age-related attrition, rather than 'impingement'.
Readers might be interested in a recent review of the literature regarding the diagnosis of "impingement syndrome".
Factors Compromising Tendon Healing
Deep surface rotator cuff fiber failure exposes the defect to joint fluid. This joint fluid prevents the formation of a fibrin clot and, thus, healing is contravened.
Furthermore, tension at the edge of the cuff tear compromises the circulation to the margin of the tendon
For these reasons, left to their own devices, cuff defects tend to progress rather than healing. An optimal cuff repair surgery will bring healthy tendon into contact with vascularized bone and exclude joint fluid from the repair site. Subsequent posts will review the principles of surgical repair in some detail.
Factors Affecting Reparability
In considering the potential for surgically restoring a durable tendon insertion to bone, the surgeon needs to consider the quality of the tissue to be used in the repair. The ability of the cuff tendon tissue to withstand tensile loads is compromised by age, disuse, steroid injections, smoking, and poor general health. These predisposing factors can dispose the cuff tendons to fail with minimal force – essentially an atraumatic fiber failure. Cuff fibers that fail atraumatically may be so constitutionally weak that they cannot hold up even if repaired back to the bone. Thus, in chronic atraumatic cuff tears there is reason to consider a non-operative approach to improving shoulder function by rehabilitating the muscle–tendon units that remain intact.
Acute, traumatic cuff detachments that result from major force application are likely to be repairable
If acute traumatic cuff tears are not repaired promptly, the muscle may undergo intramuscular contracture, atrophy, and fatty degeneration and the tendon may become progressively reabsorbed. These degenerative changes compromise the opportunity for surgical repair. Thus, as with any other tendon avulsion from bone, time is of importance in the repair of acute tears of the rotator cuff.
Loss of the rotator cuff subjects the superior glenoid to increased loads that can contribute to its erosion
Progressive upward displacement of the humeral head produces secondary changes in the coracoacromial arch
Once the humeral head has ascended so that its equator is above the residual cuff, contraction of the cuff muscles lock the humeral head in the superiorly displaced position
Chronic upwards displacement of the humeral head from cuff deficiency and superior glenoid erosion can result in cuff tear arthropathy,
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You may be interested in some of our most visited web pages including: shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery.
