The shoulder joint is the most mobile joint in the human body. This makes it particularly susceptible to instability or dislocations. The joint has only minimal bony guidance. Therefore, the surrounding soft tissues provide the necessary stability. These include
- ligaments
- the joint capsule
- the labrum (articular rim), and
- the muscles
These joint structures are crucial for stability, as the shoulder joint has a wide range of motion.
The anatomy of the shoulder, including its bony and soft tissue structures © bilderzwerg / Fotolia
Shoulder instability can be congenital or acquired:
- Congenital (also known as habitual) instability is less common; it involves anatomical abnormalities present from birth that limit stability.
- More common are acquired instabilities of the shoulder joint, which usually result from traumatic events (accidents) or exceptional stress caused by specific sports.
In cases of congenital (habitual) shoulder instability, even everyday movements can lead to a shoulder dislocation. In extreme cases, simply getting dressed or swimming can cause a dislocation. The reason for this is a lax capsular-ligamentous apparatus, which allows for excessive range of motion in the shoulder and cannot provide sufficient support. Even with minimal force, a partial dislocation (subluxation) or complete dislocation (luxation) is possible. The risk of recurrent shoulder dislocations is high in cases of habitual shoulder instability.
In the case of accident-related (traumatic) instability, the first dislocation is triggered by an accident (e.g., sports). This initial injury usually results in the labrum being sheared away from the rim of the glenoid cavity and in overstretching of the joint capsule. Bone and cartilage damage to the glenoid cavity and the humeral head also frequently occurs. These are the causes of subsequent instability of the shoulder joint.
When the shoulder is dislocated, the patient experiences severe pain and is unable to move the affected shoulder joint. Swelling, bruising, and joint effusion are also commonly observed. However, patients with instability generally experience little or no pain.
The main problem is the fear of another dislocation. As a result, the patient avoids certain movements in daily life, which can sometimes lead to significant difficulties in managing everyday activities. This can be a particularly major problem for people who work with their hands above their heads or participate in “overhead sports” (e.g., tennis).
Frequent shoulder dislocations also carry the risk of cartilage damage to the joint surface. This can lead to premature wear and tear of the shoulder joint (omarthrosis). However, this condition develops over a long period of time and manifests as increasing pain associated with movement.
For effective treatment, it is essential to accurately identify and diagnose any injuries to the joint, the capsule, the ligaments, and the bone. Understanding the mechanism of dislocation (i.e., the type and direction of the force that caused the dislocation) can be very helpful here. Therefore, obtaining a detailed history of the accident (accident history) is extremely important.
During the physical examination, the extent of shoulder instability is then assessed in comparison to the opposite side. This also allows for determining the direction in which the shoulder slipped out of the joint.
X-rays can reveal bony defects or deformities in the humeral head and the glenoid cavity. Finally, magnetic resonance imaging (MRI) can visualize the soft tissues of the capsuloligamentous complex, which are crucial for shoulder stability.
In some cases where a severe bony defect is suspected, a CT scan of the shoulder joint may be necessary.
An acute shoulder dislocation must be reduced as soon as possible. This is known in medical terms as reduction. However, since this procedure can be very painful and the patient reflexively tenses their muscles, light anesthesia and the administration of muscle relaxants are often required.
Before repositioning, however, an X-ray must be taken to rule out bone injuries in the shoulder joint. Otherwise, surgical treatment and stabilization of the bone would be necessary.
After successful reduction, short-term immobilization of the shoulder joint with special bandages is recommended to stabilize the joint. However, this immobilization should be as brief as possible (only a few days, up to a maximum of 3 weeks), as failure to do so can quickly lead to stiffness of the shoulder joint. This is followed by physical therapy to strengthen the rotator cuff muscles and the muscles that center the scapula.
An acutely dislocated shoulder (shoulder dislocation) should be reduced as soon as possible as an emergency. More than half of patients over the age of 30 to 35 do not experience another shoulder dislocation. Surgical treatment is therefore not necessary.
As mentioned above, bone fractures in the shoulder joint area—such as those involving the humeral head or the glenoid cavity—cannot generally be successfully treated by simple reduction alone. Surgical repair and stabilization of the bone using plates or screws is usually necessary. In some cases, complete joint replacement with an artificial joint prosthesis may also be necessary (for example, in the case of a comminuted fracture of the humeral head).
Other indications for surgical treatment include extensive injuries to the joint capsule and stabilizing ligamentous structures. This is frequently observed in traumatic “anterior” shoulder dislocation, which is also the most common type of shoulder dislocation (more than 90 percent of cases). In this type of dislocation, the humeral head is dislocated forward and downward, and the attachment of the joint capsule (also called the labrum) to the upper rim of the glenoid fossa is torn or damaged. It may also tear completely away from the rim of the glenoid fossa.
If the labrum of the glenoid fossa tears off completely or in parts, this injury is called a Bankart lesion. This typically indicates the need for surgical treatment, provided the patient is an active young person whose quality of life is severely impaired. For older, frail patients, immobilization for approximately two weeks may also be considered.
This often results in shrinkage of the joint capsule, leading to increased joint stability. Consequently, depending on the patient’s age and level of physical activity, there is an increased risk of one or more recurrent shoulder dislocations; for this reason, surgical treatment leads to significantly better and overall more satisfactory outcomes in young patients.
When is surgical stabilization of joint capsule damage performed?
Surgical stabilization is therefore recommended for:
- young patients (< 50)
- Almost all patients under 20 will experience further shoulder dislocations later on; therefore, surgical stabilization is generally recommended
- In patients over 50 years of age, it is essential to rule out a concurrent tendon rupture (rotator cuff tear). If such a tendon tear is detected, it must also be treated
- athletically active patients
- those participating in high-risk sports
High-risk sports include tennis, volleyball, basketball, and handball, as well as gymnastics, high jump, and weightlifting. However, this also applies to overhead work or sports involving contact with opponents
- In cases involving the dominant arm
- following repeated (recurrent) shoulder dislocations, and
- in cases of shoulder instability
The procedure can be performed as open surgery or via arthroscopy. The goal of the surgery is to achieve a stable yet fully mobile shoulder. In the video, you can see how shoulder arthroscopy is performed for diagnosis and treatment:
Surgery for shoulder instability aims to restore a stable capsular-labrum complex. The stretched joint capsule should be tightened, and in the event of a labral tear, it should be reattached to the bony glenoid cavity.
In most cases, small suture anchors are used for this purpose; these can be secured in the scapula like dowels or small screws. They are equipped with sutures used to attach the torn structures. In recent years, arthroscopic surgical techniques for this condition have advanced significantly.
The video demonstrates surgery for a Bankart lesion, in which the labrum is damaged:
Postoperative care involves early functional rehabilitation. This means that, in addition to temporary rest and immobilization (for 3 to 4 weeks in a removable shoulder sling), physical therapy should begin as soon as possible. This is initially done passively; the movements and exercises are generally performed through regular physical therapy. This helps prevent the shoulder from becoming stiff. The reconstructed soft tissue structures should be able to heal and remain permanently stable, but without stiffening or scarring.
After 4 to 6 weeks, active physical therapy and exercise therapy begin. During this phase, the patient can and should actively move the shoulder and perform more muscle-strengthening exercises.
The duration of the sick leave depends on the specific demands of the patient’s job. For jobs involving overhead work, a period of 2 to 3 months should be expected. High-risk and contact sports should not be resumed until approximately 5 to 6 months have passed.
The prognosis following surgical shoulder stabilization is good; in over 90 percent of cases, a stable joint can be achieved.
What are the typical symptoms of a shoulder dislocation?
The main symptom is a sudden, shooting, excruciating pain in the shoulder, immediately followed by an inability to move the arm. The patient usually holds the arm close to the body in a protective position. Visually, the contour of the shoulder is altered because the head of the humerus is no longer seated in the glenoid cavity, which is often recognizable as a dent beneath the shoulder muscle. In addition, numbness may occur in the arm if nerves, such as the axillary nerve, are stretched due to the dislocation.
How is a shoulder dislocation treated?
The first step is always reduction, that is, realigning the joint. This should be done as quickly as possible, often under pain medication or brief anesthesia, to relieve muscle resistance. After reduction, the shoulder is usually immobilized in a sling for several weeks. Further treatment of a shoulder dislocation depends on the patient’s age and activity level. For young patients and athletes, surgical treatment is often recommended to reattach the torn ligaments and labrum to the rim of the glenoid cavity.
When is surgery necessary after a shoulder dislocation?
Surgical treatment is usually recommended for young, active patients, as they have a very high risk of recurrent dislocation. Surgery is also advisable if there are bone injuries to the glenoid or the humeral head, or if soft tissues such as the rotator cuff or the labrum (Bankart lesion) are severely damaged. The surgery is usually performed arthroscopically using a minimally invasive approach to reattach the torn structures and stabilize the joint.
What is the difference between an anterior and a posterior shoulder dislocation?
Anterior shoulder dislocation is by far the most common type, accounting for over 90 percent of cases. In this type, the head of the humerus dislocates forward and downward out of the glenoid cavity. This typically occurs when the arm is rotated outward and abducted. A posterior shoulder dislocation is much rarer and often more difficult to detect. It is usually caused by seizures or electric shocks, during which the muscles push the head backward out of the joint.
How does a habitual dislocation develop?
Habitual shoulder dislocation usually occurs without significant trauma, i.e., without a serious accident. The cause is often a congenital weakness of the connective tissue or a malformation of the glenoid cavity, which makes the joint unstable. In these patients, the shoulder can dislocate even during everyday movements. In such cases, conservative treatment with intensive muscle training is usually the primary approach, since surgery is often less likely to be successful when the problem is solely due to tissue weakness.
What associated injuries can occur?
In the case of a traumatic first-time dislocation, structures inside the shoulder are often damaged. Frequently, the labrum tears away from the anterior rim of the glenoid cavity, a condition known as a Bankart lesion. An indentation on the head of the humerus, known as a Hill-Sachs defect, is also typical. In older patients, a rotator cuff tear often occurs as well. In addition, bone spurs or overstretching of the joint capsule can exacerbate shoulder instability.
What does follow-up care look like after a shoulder dislocation?
Regardless of whether the injury is treated conservatively or surgically, consistent follow-up care is essential. First, the arm is immobilized to allow the joint capsule and ligaments to heal. At the same time, physical therapy begins, initially maintaining range of motion passively and later specifically strengthening the muscles, particularly the rotator cuff. A strong muscle corset helps center the humeral head in the glenoid cavity and actively stabilize the joint.
When can you resume sports after a dislocation?
Returning to sports depends on the type of treatment and the specific sport. After conservative therapy, light training can often be started after 6 to 8 weeks. Contact sports such as handball or football, where the risk of re-dislocating the shoulder joint is high, should often not be resumed until 3 to 6 months have passed and only after consulting a doctor. After surgery, the rehabilitation phase until full return to sports often takes up to 6 months.
