Shoulder joint instability: Causes, Symptoms, and Treatment

Shoulder joint instability is a problem that occurs when the structures that surround the shoulder joint do not work to maintain the ball within its socket, which can be explained by the anatomy of the shoulder joint. The relatively large head of humerus contrasts with a much smaller glenoid cavity, whose joint surface is only about one-third of that of the head of the humerus. This anatomical structure of the glenohumeral joint allows a very extensive mobility of the shoulder and arm. This somewhat unfavorable size ratio of the two joint partners is compensated by various anatomically important structures that ensure that the glenoid joint remains stable and does not dislocate (luxate).

For example, the surface area of the glenoid cavity is elastically enlarged by the so-called joint lip (labrum glenoidale), and the entire shoulder joint is enclosed by a joint capsule that stabilizes and centers the head of the humerus. Optimum freedom of movement in all spatial directions of the shoulder is only possible at the expense of the stability of the joint. This explains why, of all the joints in the human body, the shoulder dislocates most frequently.

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Causes of shoulder joint instability

Shoulder joint instability can be congenital or occur after an accident. Shoulder joint instability often results in a sudden rupture of the joint lip or joint capsule as a result of traumatic dislocation of the shoulder joint

The most common injury associated with shoulder joint instability is the so-called “Bankart lesion.” This is usually caused by a dislocation of the shoulder forward in an accident, whereby the joint lip in the lower part of the anterior glenoid rim tears wholly or partially. Due to the Bankart lesion, the joint lip can no longer appropriately stabilize the shoulder joint in this area, and (further) dislocation of the shoulder can easily occur.

Symptoms of shoulder joint instability

The instability of the shoulder joint can manifest itself as severe pain. An instability and associated weakness in the shoulder region and the inability to move the shoulder are also described. There may be swelling in the shoulder joint as well as numbness and tingling (paraesthesia) around the shoulder or in the fingers.

Shoulder joint instability most often occurs after an accident, usually during a sporting activity such as football or skiing. It is not uncommon for the accident to initially lead to a luxation of the shoulder joint (dislocation of the humeral head), which must be repositioned. The risk of further dislocations that follow later is determined by

  • the anatomical conditions
  • the age of the person concerned and
  • the corresponding sporting activity
  • for sure.

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In some cases, shoulder joint instability is not preceded by accident. In this case, a detailed diagnosis should be made to determine whether surgical intervention is necessary or whether conservative (non-surgical) treatment of the instability can be attempted first.

Diagnosis of a shoulder joint instability

First of all, the patient’s medical history is thoroughly interviewed about the complaints caused by shoulder joint instability. To confirm the diagnosis, a clinical examination of the shoulder joint, as well as frailing imaging procedures, are also necessary. In this way, valuable information about pathological changes in the shoulder joint and the associated soft tissue structures can be gathered.

The standard procedure is an x-ray of the shoulder joint, sometimes a magnetic resonance tomography of the shoulder (MRI, magnetic resonance imaging of the shoulder joint) can also be informative. If an operation is to be performed to treat instability of the shoulder joint, it is usually necessary to carry out a few laboratory tests beforehand, rarely also an ECG (electrocardiogram) and an X-ray of the ribcage.

First of all, a dislocation can be distinguished from a subluxation, since no contact between the joint surfaces can be detected in the case of a complete dislocation (luxation). Depending on the cause, a distinction is also made between traumatic (with accident event) and atraumatic (without accident event) shoulder joint instability. Most acute dislocations are anterior (anterior) or anterior-inferior (anterior-inferior), only very rarely in the direction of dislocation posterior (dorsal).

Check our article about Shoulder dislocation: Causes, Symptoms, and Treatment

Therapy of shoulder joint instability

Conservative therapy

A dislocated shoulder should be repositioned as soon as possible. An X-ray check should be carried out beforehand to rule out bony injuries. If necessary, the reduction can be carried out under a short anesthetic. If the shoulder has been previously dislocated, the dislocation may be performed without anesthesia.

In some cases, conservative (non-surgical) treatment may also be possible, taking into account the individual anatomical causes of shoulder instability. In this case, pain is alleviated with suitable painkillers, and after the dislocation, the shoulder is immobilized for a short time (e.g., in a Gilchrist bandage). Subsequently, an intensive training of the muscles (especially the back muscles) under physiotherapeutic guidance is recommended.

Surgical therapy

The surgical therapy of shoulder instability aims to correct the existing injury to restore the normal anatomy as accurately as possible. In most cases, shoulder instability surgery is performed arthroscopically, i.e., as part of a joint endoscopy. This surgical technique is minimally invasive, as only two to three small skin incisions are usually required.

Only in very rare cases may an open surgical procedure be necessary, for example, if bony splinters are caused by a shoulder joint luxation and “float around” freely in the joint space. In an arthroscopic procedure, optics with a camera system and corresponding special instruments are inserted through the small openings in the shoulder joint. In this way, the existing damage to the shoulder joint can be repaired. Often, the torn capsule or torn joint lip is reattached to the bone with the help of a thread anchor. These sutures are bioresorbable implants, which means that they dissolve after a certain time and do not need to be removed. After this time, the anatomical structure has healed again.

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Postoperative treatment after the operation

Immediately after the operation, the patient is fitted with a shoulder splint (orthosis), which allows only minimal mobility of the shoulder joint. Due to the protection, stabilization and scarring process can begin, which usually leads to a stable shoulder again. Temporarily, there is a limitation of mobility in the shoulder, especially by avoiding abduction and external rotational movements (this could dislocate the shoulder again). The prospects of success with surgical treatment of shoulder joint instability are excellent, with over 95 percent of patients achieving stability of the shoulder joint again. The prerequisite for this is optimal follow-up treatment according to the recommendations of the attending physician or therapist.

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