Rotator cuff

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Rotator cuff
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Muscles on the dorsum of the scapula, and the Triceps brachii.
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The scapular and circumflex arteries.
Gray's subject #123

The rotator cuff (rotor cuff) is an anatomical term given to the group of muscles and their tendons that act to stabilize the shoulder. Along with the teres major and the deltoid the four muscles of the rotator cuff make up the six scapulohumeral (those that connect to the humerus and scapula) muscles of the human body.

Function

These muscles arise from the scapula and connect to the head of the humerus forming a cuff at shoulder joint. They are important because they hold the head of the humerus in the small and shallow glenoid fossa of the scapula. The glenohumeral joint is often likened to a golf ball sitting on a golf tee. During elevation of the arm, the rotator cuff compresses the glenohumeral joint 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.

Some anatomists dispute the importance of the rotator cuff. According to them the m. biceps brachii is the key factor in keeping the bones together.

Muscles comprising rotator cuff

Muscle Origin on scapula Attachment on humerus Function Innervation
Supraspinatus muscle supraspinous fossa greater tubercle abducts the arm Suprascapular nerve (C5)
Infraspinatus muscle infraspinous fossa greater tubercle laterally rotates the arm Suprascapular nerve (C5-C6)
Teres minor muscle lateral border greater tubercle laterally rotates the arm Axillary nerve (C5)
Subscapularis muscle subscapular fossa lesser tubercle medially rotates the humerus Subscapular nerve (C5-C6)

Injuries

Rotator cuff tear

This group of tendons 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 "wear and tear" of the tendons under the acromion. It is an injury frequently sustained by athletes whose duties involve making repetitive throws, such as baseball pitchers, American football quarterbacks, or swimmers. It is commonly associated with motions that require repeated overhead motions or forceful pulling motions.

Rotator cuff impingement

A systematic review of relevant research found that the accuracy of the physical examination is low.[1] The Hawkins-Kennedy test[2][3] and Hawkins-Kennedy test have a sensitivity of approximately 80% to 90% for detecting impingement. The infraspinatus and supraspinatus[4] tests have a specificity of 80% to 90%.[1]

Treatment

Reduce Pain & Swelling

As with all muscle injuries, R.I.C.E. is the modality recommended by MDs, DOs, Physical Therapists, Athletic Trainers, and Chiropractors.

R=Rest I=Ice C=Compression E=Elevation

  • Rest means stop doing any exercise or movement that causes pain. Pain is an indication the muscle tears are not healed and the tears are increasing.
  • Icing numbs the area to decrease pain and also constricts the blood vessels to minimize swelling and bruising. Never ice for more than 15-20 minutes at a time as over icing will produce a different injury to the soft tissues.
  • Compression also limits the swelling.
  • Elevation doesn't really apply to the shoulder except when bending over or lying down. When the torn muscles are below the heart, more blood and serum can accumulate, increasing swelling and throbbing.

Cold compression therapy is very useful for all muscle tears and strains as it reduces pain and swelling. Using a cold compression therapy wrap for 15 minutes before sleeping can aid in reducing the pain which causes a restless nights sleep.

Strengthening

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.

Description Beginning End
The most effective is the side-lying abduction, which activates the supraspinatus, subscapularis and infraspinatus. The side-lying abduction involves the person selecting a dumbbell of low weight initially when first training - four or five kilograms. The lifter lies on a bench sideways, with the arm next to his side and slightly flexed at the elbow. The dumbbell should then be raised towards the ceiling to a 45 degree angle, with the arm still flexed and close to the body, at a pace of two seconds up and four seconds down. The side-lying abduction does not involve the teres minor, but moderately involve the deltoid muscles, making it an excellent all-round shoulder exercise. 150px 150px
Another exercise is the propped external rotator, which targets the infraspinatus and teres minor. The lifter should sit perpendicular to the barbell, with his arm flexed at 90 degrees at the elbow and the forearm resting parallel on the barbell. Again, selecting a dumbbell of modest weight if just beginning, raise the dumbbell up until the forearm points up. Slowly lower the dumbbell and repeat, exercising both arms. 150px 150px
The final exercise is the lateral raise with internal rotation (LRIR). Grasping a dumbbell in both hands, the lifter should internally rotate his arm so that his extended thumbs point towards the floor - as if the lifter is emptying a drink into a bin. The lifter should then raise his arms sideways, with the thumbs still pointing downwards, until the dumbbells are just below the shoulders. The LRIR primarily targets the supraspinatus. 150px 150px

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 in the population.

Additional images

References

  1. 1.0 1.1 Hegedus EJ, Goode A, Campbell S; et al. (2007). "Physical Examination Tests of the Shoulder: A Systematic Review with Meta-analysis of Individual Tests". PMID 17720798. doi:10.1136/bjsm.2007.038406. 
  2. ShoulderDoc.co.uk Shoulder and Elbow Surgery. "Hawkins-Kennedy Test". Retrieved 2007-09-12.  (video)
  3. Brukner P, Khan K, Kibler WB. "Chapter 14: Shoulder Pain". Retrieved 2007-08-30. 
  4. ShoulderDoc.co.uk Shoulder and Elbow Surgery. "Empty Can/Full Can Test". Retrieved 2007-09-12.  (video)

External links

de:Oberarm#Rotatorenmanschettehe:מסובבי הכתף nl:Rotatorcuffspierenfi:Kiertäjäkalvosin sv:Rotatorkuff


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