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.
- 1 Structure
- 2 Function
- 3 Clinical significance
- 4 Prevention
- 5 Rehabilitation of rotator cuff injury
- 6 Epidemiology
- 7 Additional images
- 8 See also
- 9 References
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 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.
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%.
Shoulder rotator cuff injuries can easily be prevented if individuals use correct form when exercising, performing activities and sports, during accidental falls, or according to lifestyle habits. Further by preventing the first rotator cuff tear you also prevent the occurrence of another injury in the future.
According to a study which measured tendon length against the size of the injured rotator cuff researchers learned that as rotator cuff tendons decrease in length the average rotator cuff severity is proportionally decreased as well  This shows that larger individuals are more likely to suffer from a severe rotator cuff tear if they do not tighten the shoulder muscles around the joint. We can then attempt to prescribe exercise to individuals if they have particular body measurements as prevention.
Another study observed 12 different positions of movements and their relative correlation with injuries occurred during those movements. The evidence shows that putting the arm in a neutral position relieves tension on all ligaments and tendons.
One article observed the influence of stretching techniques on preventative methods of shoulder injuries. Increased velocity of exercise increases injury, however, beginning a fast movement exercise with a slow stretch may cause muscle/tendon attachment to become more resistant to tearing.
When exercising it is also found to be imperative to exercise the shoulder as a whole and not one or two muscle groups. When the shoulder muscle is exercised in all directions, such as external rotation, flexion and extension, or vertical abduction it is less likely to suffer from a tear of the tendon.
Even lifestyle habits have been accredited as methods to preventing shoulder injury. In a study of five hundred seventy-six patients who underwent shoulder repair surgery, the average age for patients who were who were noted as smoking tobacco cigarettes regularly was significantly lower than for patients who were non-smokers.
Reduce pain and swelling
As with all muscle injuries, R.I.C.E. is an initial response to injury recommended by health providers:
- Rest means ceasing movement of the affected area.
- Icing uses ice to reduce inflammation.
- Compression limits the swelling.
- Elevation involves placing the area higher to reduce inflammation and swelling.
Cold compression therapy shoulder wraps facilitate the icing and compression of an otherwise difficult body area to ice and compress.
Depending on severity of symptoms, further imaging with radiograph, or MRI may be warranted to see if surgery or an underlying bone injury exists.
Posture and sleeping positions
Postures and sleeping positions may be modified to provide relief. But as your shoulder begins to heal, sleeping positions may vary considerably.
The rotator cuff can be strengthened to rehabilitate shoulder injuries, and prevent future ones. There are different exercises to target the individual rotator cuff muscles.
|The most effective is the side-lying external rotation, which activates the supraspinatus, subscapularis, infraspinatus and teres minor.
Lie on a bench sideways, with the affected arm next to the side and flexed about 90 degrees at the elbow. Rotate the upper arm outward, keeping the elbow flexed and the arm close to the body, until the lower arm is perpendicular to the ceiling (see picture). For added resistance, use a dumbbell. Pace at two seconds out and four seconds back.
|The propped external rotator targets the infraspinatus and teres minor.
Sit perpendicular to the dumbbell with arm flexed at 90 degrees at the elbow, and the forearm resting parallel on the dumbbell. Raise the dumbbell up until the forearm points up. Slowly lower the dumbbell and repeat, exercising both arms.
The posterior deltoid also aids in external rotation. Like the posterior deltoid, both the infraspinatus and teres minor also contribute to transverse extension of the shoulder, such as during a bent over row to the chest. They can be trained in this way besides isolating the external rotation action.
|The lateral raise with internal rotation (LRIR) primarily targets the supraspinatus.
Grasping a dumbbell in each hand, internally rotate the arms so that the thumbs point towards the floor when extended (as if emptying a drink into a bin). Raise the arms sideways, keeping the thumbs pointing downwards, until the dumbbells are just below the shoulders.
This exercise is sometimes called a lateral raise.
Strengthening the rotator cuff allows for increased loads in a variety of exercises. When weightlifters are unable to increase the weight they can lift on a pushing exercise (such as the bench press or military press) for an extended period of time, strengthening the rotator cuff can often allow them to begin making gains again. It also prevents future injuries to the glenohumeral joint, balancing the often-dominant internal rotators with stronger external rotators. Finally, exercising the rotator cuff can lead to improved posture, as without exercise to the external rotator, the internal rotators can see a shortening, leading to tightness. This often manifests itself as rounded shoulders.
Non-operative treatment is often the first line of treatment for rotator cuff injuries. If the tendons are strained or torn less than 50%, they respond well to an aggressive non-operative approach. Non-operative measures can include physical therapy, oral or injected medications, biologic augmentation such as PRP, ultrasound therapy, dry needling, and other modalities. It will often take 3 months to recover with non-operative measures.
Even for full thickness rotator cuff tears, conservative care (i.e., non-surgical treatment) outcomes are usually reasonably good. However, many patients still suffer disability and pain despite non-surgical therapies. For massive tears of the rotator cuff, surgery has shown durable outcomes on 10 year follow-up. However, the same study demonstrated ongoing and progressive fatty atrophy and repeat tears of the rotator cuff. Shen has shown that MRI evidence of fatty atrophy in the rotator cuff prior to surgery is predicative of a poor surgical outcome. If the rotator cuff is completely torn, surgery is usually required to reattach the tendon to the bone.
Surgery for the rotator cuff
Surgery for the rotator cuff can be for complete tears, or partial tears/strains that fail to get better. If a torn rotator cuff goes untreated for too long, it may become un-repairable and so shoulder pain should not be ignored. Surgery often consists of removing damaged tissue and repairing the good tissue back to the bone. Bone spurs and inflammation (bursitis) is also removed to try to prevent re-tears. all arthroscopic rotator cuff repairs can fix most tears through 4-5 small incisions. On occasion a patch needs to be placed on the rotator cuff tendons which requires a larger incision. Many times, the biceps tendon is damaged with rotator cuff tears and may also require biceps tenodesis surgery at the same time.
Rehabilitation of rotator cuff injury
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.
Incidence of a rotator cuff tear
A rotator cuff tear can be caused by the weakening of the rotator cuff tendons. This weakening can be caused by age or how often the rotator cuff is used. Adults over the age of 60 are more susceptible to a rotator cuff tear. According to a study in the Journal of Orthopaedic Surgery and Traumatology the frequency of rotator cuff tears can increase with age. The study shows the participants that were the ages of 70–90 years old had a rate of rotator cuff tears that were 1 to 5. The participants who were 90+ years old the frequency of a rotator cuff tear jumped to 1 to 3. This study shows that with an increase in age there is also an increase in the probability of a rotator cuff tear.
Prevalence of a rotator cuff tear
According to a study in the Journal of Orthopaedics the prevalence of a rotator cuff tear was considerably greater in males than in females within the ages of 50–60 years old, within the ages of 70–80 years old there wasn’t much difference in prevalence. The data of this study showed that the prevalence of a rotator cuff tear in the general population is 22.1%  Yamamoto et al performed a medical examination on 683 people whom live in a mountain village. The purpose of this study was to determine the prevalence of a rotator cuff tear among a population. Yamamoto found that among the mountain village population, rotator cuff tears were present in 20.7% of the village population. In both of these studies we see that the percentages of the prevalence of a rotator cuff tear are very close in number so these numbers show us the prevalence of rotator cuff tears in the general population.
Risk factors of a rotator cuff tear
There are some risk factors of experiencing a rotator cuff tear that we can not change; age, body mass index, height. Recurrent lifting and overhead motions are at risk for rotator cuff tears. People who have jobs that involve a lot of overhead work like, carpenters or painters, are at risk of also experiencing a rotator cuff tear. People who play sports that involve overhead motions like; swimming, baseball, tennis, and a football quarterback, are at a greater risk of experiencing a rotator cuff tear.
This article uses anatomical terminology; for an overview, see anatomical terminology.
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