Position and function
The supraspinatus tendon is the attachment tendon of the supraspinatus muscle (upper bone muscle). This muscle has its origin at the back of the shoulder blade and attaches to the head of humerus via its tendon. The muscle is mainly responsible for spreading the arm away from the body (abduction), especially at an angle of more than 60°. Together with three other muscles (musculus infraspinatus, musculus subscapularis and musculus teres minor) it forms the so-called rotator cuff. This group of muscles also serves to rotate the upper arm (inward and outward), but its most important task is to stabilize the shoulder joint, which is otherwise relatively free to move and has little security.
Diseases and injuries
Since the supraspinatus tendon is anatomically closely related to bursae and the acromion, it is particularly susceptible to injury and is therefore a common cause of shoulder pain. Three typical clinical pictures are in the foreground here: Impingement syndrome, calcifications (which can very often be caused by degenerative changes) and rotator cuff rupture, in which the supraspinatus tendon tears particularly often. In impingement syndrome, there is not enough space in the shoulder joint for all structures, which is why certain parts of the joint collide unnaturally, causing pain to the person affected.
As a result, the mobility of the shoulder joint is sometimes severely restricted. This can have very different causes, but the most common cause is a thickening of the supraspinatus tendon. This can have various reasons: Either it has been exposed to long-term overloading or it has swollen as a result of inflammation or degenerative changes.
When the arm is spread sideways, the supraspinatus tendon always moves towards the middle of the body and slides between the head of humerus and the acromion. However, if it is now thickened, the area under the acromion (the subacromial space) is thereby reduced too much and the structures located within it are narrowed. This means that tendons rub directly against each other or against the bone or bursae and different tissues are irritated as a result.
This leads to pain, especially during abduction of the arm between 60 and 120°, which is why some people refer to this disorder as “painful bow”. In some cases, the pain can radiate far into the upper arm and may also exist at night when the patient turns to the diseased side. Surgically, an impingement syndrome can usually be well treated.
Although rotator cuff rupture is more common in association with impingement syndrome, it does not necessarily have anything to do with it. In the course of life, the supraspinatus tendon becomes thinner and thinner and less tear-resistant due to constant stress. This is due to the natural wear and tear of the tendon and partly to degenerative changes caused by it.
Once the tendon is “thinned out” in this way, it is easy for it to become so overstretched as a result of even minimal violence, injury or accident that it tears or even breaks. In larger accidents, such as a fall that is caught by the outstretched arm, even a previously undamaged tendon can tear. The complaints a patient complains of are, depending on the extent of the tear, pain, restricted movement (especially in abduction and external rotation) and a reduction in strength.
If the tendon is not completely severed, the rupture is usually followed by conservative therapy (with medication and physiotherapy). Although this does not restore the tendon, normal everyday use can usually be restored within a short time. If no success is achieved or if the tendon is completely torn off, there is usually no way around surgery.
Another common disease of the supraspinatus tendon is tendinosis or tendinitis calcarea, i.e. calcification of the tendon or tendon attachment. Here, calcification occurs either under or on the tendon itself, which in turn leads to inflammation of the tendon. This inflammation then brings the typical signs of inflammation with it, especially pain, swelling, redness and a restriction of movement of the shoulder joint.The exact cause of these changes could not be finally clarified until today, only partly they are degeneratively caused (thus a form of the Arthrose), partly they occur however evenly also without any recognizable reason.
With the help of an X-ray image, the calcifications can be easily recognized and the diagnosis is therefore relatively simple. Since the pain can be very severe and calcification can often lead to a rupture of the supraspinatus tendon at some point, therapy is generally recommended. Depending on the patient, this therapy can be carried out conservatively (i.e. with cooling, medication, physiotherapy or, more recently, so-called extracorporeal shock wave therapy [ESWT], in which the calcification deposits in the shoulder are shattered from the outside by low-frequency shock waves, although this is still controversial despite good results) or, in more severe cases, by surgery in which the calcifications are removed. Unfortunately, even after an operation, the relapse rate is not to be sneezed at and, in addition, calcifications also heal spontaneously, which is why the pros and cons of carrying out an operation must always be weighed up thoroughly by doctor and patient.
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