Accurate diagnosis and effective treatment of rotator cuff disease relies on an appreciation of shoulder anatomy and bio mechanics. Structures that contribute to normal function will also influence pathologic conditions of the rotator cuff. An awareness of the discerning features of a patient's history and physical examination, and an understanding of potential contributions from surrounding structures will assist in developing a differential diagnosis and formulating an effective treatment plan.
The rotator cuff is formed from the coalescence of the tendinous insertions of the subscapularis, supraspinatus, infra-spinatus, and teres minor muscles into one continuous band near their insertions on the greater and lesser tuberosities of the proximal humerus. This arrangement suggests that the muscles of the cuff function in concert. In fact, the name "rotator" cuff may be a misnomer; the major function of the rotator cuff is to depress and stabilize the humeral head, effectively compressing the glenohumeral joint to provide a stable fulcrum for arm movement.1-3
Abduction strength, although powered by the deltoid, requires a stable fulcrum provided by a functioning rotator cuff. Glenohumeral stability in mid-range relies on functioning rotator cuff muscles that, along with scapular stabilizers4 and the deltoid,5 permit balanced muscle pull and concavity compression. As passive restraints to glenohumeral translation are lax in mid-range, joint stability in this position is provided by dynamic stabilizers. A more complete discussion of gleno-humeral joint stability is presented in other chapters. With respect to rotator cuff pathomechanics, specifically large rotator cuff tears, it is important to appreciate the effect of transverse plane force coupling in which the anterior generated subscapu-laris force and anterior supraspinatus are balanced by the posterior supraspinatus, infraspinatus, and teres minor. Balancing these forces with only partial repair of large tears, when complete repair is not possible, is thought to provide a more stable fulcrum for shoulder motion, leading to functional improvement.1,3
The concept of functional linking of force couples was popularized by Burkart6 who described the phenomenon of the cuff acting as a single functional unit, with individual forces balancing one another to produce the desired functional effect. The rotator cuff cable is a normal thickening in the intact cuff that is seen arthroscopically from the articular, undersurface side of the cuff (Fig. 25-1). This thickening in the capsule and overlying tendon extends from its insertion just posterior to the biceps tendon to the inferior border of the infraspinatous tendon6,7 and is thought to allow the forces across the rotator cuff to be dispersed in a manner similar to a suspension bridge. In this sense, the rotator cable transfers the stress from the supraspinatus and infraspinatus muscles to the terminal insertions of the cable, by directing the force along its length. This organization of force
Was this article helpful?
Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.