Muscles on the dorsum of the scapula, and the Triceps brachii.
The scapular and circumflex arteries.
In anatomy, the rotator cuff (sometimes incorrectly called a "rotator cup", "rotor cuff", or "rotary cup") is a group of muscles and their tendons that act to stabilize the shoulder. The four muscles of the rotator cuff are over half of the seven scapulohumeral muscles. The four muscles are the supraspinatus muscle, the infraspinatus muscle, teres minor muscle, and the subscapularis muscle.
Muscles composing rotator cuff
|Muscle||Origin on scapula||Attachment on humerus||Function||Innervation|
|Supraspinatus muscle||supraspinous fossa||superior and middle facet of the greater tuberosity||abducts the arm||Suprascapular nerve (C5)|
|Infraspinatus muscle||infraspinous fossa||posterior facet of the greater tuberosity||externally rotates the arm||Suprascapular nerve (C5-C6)|
|Teres minor muscle||middle half of lateral border||inferior facet of the greater tuberosity||externally rotates the arm||Axillary nerve (C5)|
|Subscapularis muscle||subscapular fossa||lesser tuberosity (60%) or humeral neck (40%)||internally rotates the humerus||Upper and Lower subscapular nerve (C5-C6)|
The supraspinatus muscle fans out in a horizontal band to insert on the superior and middle facets of the greater tubercle. The greater tubercle projects as the most lateral structure of the humeral head. Medial to this, in turn, is the lesser tuberosity of the humeral head. The subscapularis muscle origin is divided from the remainder of the rotator cuff origins as it is deep to the scapula
The four tendons of these muscles converge to form the rotator cuff tendon. These tendinous insertions along with the articular capsule, the coracohumeral ligament, and the glenohumeral ligament complex, blend into a confluent sheet before insertion into the humeral tuberosities. The insertion site of the rotator cuff tendon at the greater tuberosity is often referred to as the footprint. The infraspinatus and teres minor fuse near their musculotendinous junctions, while the supraspinatus and subscapularis tendons join as a sheath that surrounds the biceps tendon at the entrance of the bicipital groove. The supraspinatus is most commonly involved in a rotator cuff tear.
The rotator cuff muscles are important in shoulder movements and in maintaining glenohumeral joint (shoulder joint) stability. These muscles arise from the scapula and connect to the head of the humerus, forming a cuff at the shoulder joint. They hold the head of the humerus in the small and shallow glenoid fossa of the scapula. The glenohumeral joint has been analogously described as a golf ball (head of the humerus) sitting on a golf tee (glenoid fossa).
During abduction of the arm, moving it outward and away from the trunk, the rotator cuff compresses the glenohumeral joint, a term known as concavity compression, in order to allow the large deltoid muscle to further elevate the arm. In other words, without the rotator cuff, the humeral head would ride up partially out of the glenoid fossa, lessening the efficiency of the deltoid muscle. The anterior and posterior directions of the glenoid fossa are more susceptible to shear force perturbations as the glenoid fossa is not as deep relative to the superior and inferior directions. The rotator cuff's contributions to concavity compression and stability vary according to their stiffness and the direction of the force they apply upon the joint.
Despite stabilizing the glenohumeral joint and controlling humeral head translation, the rotator cuff muscles also perform multiple functions, including abduction, internal rotation, and external rotation of the shoulder. The infraspinatus and subscapularis have significant roles in scapular plane shoulder abduction (scaption), generating forces that are two to three times greater than the force produced by the supraspinatus muscle. However, the supraspinatus is more effective for general shoulder abduction because of its moment arm. The anterior portion of the supraspinatus tendon is submitted to significantly greater load and stress, and performs its mainfunctional role.
Rotator cuff tear
The tendons at the ends of the rotator cuff muscles can become torn, leading to pain and restricted movement of the arm. A torn rotator cuff can occur following a trauma to the shoulder or it can occur through the "wear and tear" on tendons, most commonly the supraspinatus tendon found under the acromion.
Rotator cuff injuries are commonly associated with motions that require repeated overhead motions or forceful pulling motions. Such injuries are frequently sustained by athletes whose actions include making repetitive throws, athletes such as baseball pitchers, softball pitchers, American football players (especially quarterbacks), cheerleaders, weightlifters (especially powerlifters due to extreme weights used in the bench press), rugby players, volleyball players (due to their swinging motions), water polo players, rodeo team ropers, shot put throwers (due to using poor technique), swimmers, boxers, kayakers, western martial artists, fast bowlers in cricket, tennis players (due to their service motion) and tenpin bowlers due to the repetitive swinging motion of the arm with the weight of a bowling ball. This type of injury also commonly affects orchestra conductors, choral conductors, and drummers (due, again, to swinging motions).
After experiencing a rotator cuff tear, minimally invasive surgery is needed in order to repair the torn tendon. After surgery, the rehabilitation of the rotator cuff is necessary in order to regain maximum strength and range of motion within the shoulder joint. Physical therapy progresses through four stages, increasing movement throughout each phase. The tempo and intensity of the stages are solely reliant on the extent of the injury and the patient’s activity necessities. The first stage requires immobilization of the shoulder joint. The shoulder that is injured is placed in a sling and shoulder flexion or abduction of the arm is avoided for 4 to 6 weeks after surgery (Brewster, 1993). Avoiding movement of the shoulder joint allows the torn tendon to fully heal. Once the tendon is entirely recovered, passive exercises can be implemented. Passive exercises of the shoulder are movements in which a physical therapist maintains the arm in a particular position, manipulating the rotator cuff without any effort by the patient. These exercises are used to increase stability, strength and range of motion of the Subscapularis, Supraspinatus, Infraspinatus, and Teres minor muscles within the rotator cuff. Passive exercises include internal and external rotation of the shoulder joint, as well as flexion and extension of the shoulder.
As progression increases after 4–6 weeks,active exercises are now implemented into the rehabilitation process. Active exercises allow an increase in strength and further range of motion by permitting the movement of the shoulder joint without the support of a physical therapist. Active exercises include the Pendulum exercise (as shown in Image 2), which is used to strengthen the Supraspinatus, Infraspinatus, and Subscapularis. External rotation of the shoulder with the arm at a 90-degree angle is an additional exercise done to increase control and range of motion of the Infraspinatus and Teres minor muscles. Various active exercises are done for an additional 3–6 weeks as progress is based on an individual case by case basis. At 8–12 weeks, strength training intensity will increase as free-weights and resistance bands will be implemented within the exercise prescription.
Rotator cuff impingement
A systematic review of relevant research found that the accuracy of the physical examination is low. The Hawkins-Kennedy test has a sensitivity of approximately 80% to 90% for detecting impingement. The infraspinatus and supraspinatus tests have a specificity of 80% to 90%.
|This section requires expansion. (October 2014)|
- This article uses anatomical terminology; for an overview, see anatomical terminology.
- Tnation article Push-Ups, Face Pulls, and Shrugs ...for Strong and Healthy Shoulders! by Bill Hartman and Mike Robertson: The rotator cuff, of course. (Or for those of you from Indiana, that would be your "rotary cup").
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