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 Additional images
- 5 See also
- 6 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 cheerleaders, baseball pitchers, softball pitchers, American football players (especially quarterbacks), 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%.
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.
This is an excellent all-around shoulder exercise.
|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.
The rehab for rotator cuff surgery falls into three basic categories; some damage to the tendons with surgery consisting of debridement, removing spurs and cleaning out inflammation, tears requiring repair with excellent quality tendon tissue, and tears requiring repair with poor quality tendon tissue. The first category, rehab consists of early active and passive range of motion exercises focused on maintaining range of motion for 4 weeks and then strengthening and return to sports from weeks 4-8. Repaired tendons with excellent quality will begin full passive motion early, start active motion from weeks 4-8, strengthening from 8-12 and return to sports after 3–4 months. Repairs with poor tissue quality will have no motion early on, start passive motion after 2–4 weeks, active at 6–8 weeks, strengthening at 4 months and return to sports at 6 months. Your doctor will guide you through the rehabilitation process.
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").
- Morag Y, Jacobson JA, Miller B, De Maeseneer M, Girish G, Jamadar D (2006). "MR imaging of rotator cuff injury: what the clinician needs to know". Radiographics 26 (4): 1045–65. doi:10.1148/rg.264055087. PMID 16844931.
- "Khazzam et al. American Journal of Orthopedics - Open Shoulder Stabilization Using bone block technique for treatment of chronic glenohumeral instability associated with glenoid deficiency.". American Journal of Orthopedics. July 2009.
- Escamilla RF, Yamashiro K, Paulos L, Andrews JR. Shoulder muscle activity and function in common shoulder rehabilitation exercises. Sports Med 2009; 39:663-85.
- Arend CF. Ultrasound of the Shoulder. Master Medical Books, 2013. Free chapter on anatomy and function of rotator cuff muscles available at ShoulderUS.com
- ItoiE, Berglund LJ, Grabowski JJ, et al. Tensile properties of the supraspinatustendon. J Orthop Res 1995; 13:578-84.
- Hegedus EJ, Goode A, Campbell S, et al. (February 2008). "Physical examination tests of the shoulder: a systematic review with meta-analysis of individual tests". British Journal of Sports Medicine 42 (2): 80–92. doi:10.1136/bjsm.2007.038406. PMID 17720798.
- ShoulderDoc.co.uk Shoulder and Elbow Surgery. "Hawkins-Kennedy Test". Retrieved 2007-09-12. (video)
- Brukner P, Khan K, Kibler WB. "Chapter 14: Shoulder Pain". Retrieved 2007-08-30.
- ShoulderDoc.co.uk Shoulder and Elbow Surgery. "Empty Can/Full Can Test". Retrieved 2007-09-12. (video)
- Maschi, PT, DPT, CSCS, Robert. "Chapter 40 Rotator Cuff Repair: Arthroscopic and Open". Unknown. p. 449. Retrieved 2010-04-28.
- Baydar M, Akalin E, El O, et al. (April 2009). "The efficacy of conservative treatment in patients with full-thickness rotator cuff tears". Rheumatology International 29 (6): 623–8. doi:10.1007/s00296-008-0733-2. PMID 18850322.
- Zumstein MA, Jost B, Hempel J, Hodler J, Gerber C (November 2008). "The clinical and structural long-term results of open repair of massive tears of the rotator cuff". The Journal of Bone and Joint Surgery. American Volume 90 (11): 2423–31. doi:10.2106/JBJS.G.00677. PMID 18978411.
- Shen PH, Lien SB, Shen HC, Lee CH, Wu SS, Lin LC (2008). "Long-term functional outcomes after repair of rotator cuff tears correlated with atrophy of the supraspinatus muscles on magnetic resonance images". Journal of Shoulder and Elbow Surgery 17 (1 Suppl): 1S–7S. doi:10.1016/j.jse.2007.04.014. PMID 17931908.
- Matsen, Frederick A.; Winston J. Warme (19 August 2008). "Repair of Rotator Cuff Tears: Surgery for shoulders with torn rotator cuff tendons can lessen shoulder pain and improve function without acromioplasty". University of Washington School of Medicine. Retrieved 5 July 2009.