The supraspinatus muscle is the name given to the upper limb muscle. It is part of the rotator cuff.
What is the supraspinatus muscle?
The supraspinatus muscle is the upper limb muscle. Together with the infraspinatus muscle (lower limb muscle), the subscapularis muscle (lower shoulder blade muscle) and the teres minor muscle (small round muscle), it forms the rotator cuff. This has the function of holding the humeral head in the joint socket. The supraspinatus muscle is located in the shoulder joint. The skeletal muscle is located under the trapezius muscle (trapezius muscle) and extends from the upper section of the scapula to the top of the humerus. At this point, the muscle is attached to a bony prominence. The supraspinatus muscle is important for angling the upper arm to the side as well as rotating it in the outward direction. The shoulder muscle as well as its tendon are not infrequently affected by impingement syndrome or tears.
Anatomy and structure
The origin of the supraspinatus muscle is found on the dorsal aspect of the scapula at the supraspinous fossa. This is a scapular depression over the scapular bone (spina scapulae). The scapula can be palpated on the scapula as an ascending bony prominence through the skin. The scapula side is largely filled by musculus supraspinatus. Some fibers originate at the fascia supraspinata. The supraspinatus muscle is completely covered dorsally by the trapezius muscle and partially covered laterally by the deltoid muscle. The attachment of the supraspinatus muscle lies at the upper facet of the greater tuberosity. This refers to a larger bony prominence on the humerus. It is located approximately laterally in the lower section of the bone head. Between the insertion and origin, the humeral muscle passes through a shoulder constriction. This is created by the humeral head and the acromion. The supraspinatus tendon acts as the insertion tendon of the supraspinatus muscle, which has an anatomically close relationship with the bursae, which are located below the acromion. The course of the tendon extends to the caput humeri (humeral head). At this point, it attaches laterally to the greater humeral tuberosity. There is also an adhesion between the tendon and the shoulder joint capsule. Between the acromion and the end tendon lies the subacromial bursa. This bursa provides protection against increased bone wear. The supraspinatus muscle is supplied by the suprascapular nerve, which forms a branch of the brachial plexus.
Function and tasks
Together with the deltoid muscle, the supraspinatus muscle provides spreading as well as external rotation of the upper arm. When the arm is applied and has an abduction angle of less than 15 degrees, it is considered the most important player in the spreading motion of the arm. Following this, the main function is performed by the deltoid muscle. Also among the tasks of the upper spine muscle is the tensioning of the shoulder joint capsule. Thus, the rotator cuff muscle is fused with the joint capsule and, by tightening it, causes no entrapment of capsular folds when the arm is raised. Together with the other rotator cuff muscles, the supraspinatus muscle displaces the humeral head toward the center at the beginning of shoulder motion, centering it on the cavitas glenoidalis scapulae.
Diseases
Naturally, the tendon of the supraspinatus muscle is subject to severe stresses throughout life. Thus, from the age of 50, there is a risk of spontaneous rupture of the supraspinatus tendon. This injury becomes noticeable through loss of function of the supraspinatus muscle as well as considerable shoulder pain. External rotation as well as turning the arm away from the trunk can only be performed with difficulty or even not at all. Supraspinatus rupture is the most common variant of rotator cuff tears. The reason for the injury is the strong mechanical stress to which the supraspinatus tendon is exposed. Thus, partial tears or complete tendon ruptures can occur due to constant overloading, accidents or the natural aging process. The complaints mostly appear after minor overloads or due to physical activities that are unfamiliar.Typical symptoms include shooting pain or discomfort at night during jerky applications of force or overhead movements. A rupture of the supraspinatus tendon is usually already diagnosed by physical examination by a doctor or by sonography (ultrasound examination). Changes can also be seen on an x-ray. However, X-ray examinations only provide information about the impairments at a later stage. Thus, if a rotator cuff tear is suspected, a magnetic resonance imaging (MRI) scan is performed in most cases. Because a torn supraspinatus tendon cannot be healed by conservative measures, surgery must be performed. In this procedure, the surgeon fixes the torn portions of the tendon to the humeral head. Another common disorder of the supraspinatus muscle is impingement syndrome. In this case, the supraspinatus tendon becomes entrapped under the bony prominence of the acromion. The affected person therefore suffers from pronounced pain. The most common causes of the constriction syndrome are considered to be injuries or degeneration of the rotator cuff. Patients are then no longer able to raise their arm above their shoulder. Doctors differentiate between outlet impingement and non-outlet impingement. Outlet impingement is when there is a narrowing of the subacromion by the adjacent anatomical structures. This may be bone deposits (osteophytes) or an acromion spur. Non-outlet impingement, on the other hand, is caused by damage to the rotator cuff muscles or inflammation of the shoulder joint capsule. Inflammation due to an injury is a possible cause. Invariably, the impairments are associated with severe pain in the supraspinatus muscle or the supraspinatus tendon.
