Shoulder instability

The shoulder is made up of three main bones: the humerus, the clavicle and the scapula. The glenohumeral joint is one of the most highly stressed joints in the human body, and relies on a balance between static and dynamic structures.

• Bone structures: the head of the humerus articulates with the glenoid, a shallow surface of the scapula. This joint offers great mobility but little intrinsic stability.
• Passive stabilisers: the joint capsule, the glenohumeral ligaments and the labrum (a fibro-cartilaginous ring) play a key role in limiting excessive movement.
• Active stabilisers: the rotator cuff (made up of several muscles such as the supraspinatus and subscapularis) maintains the dynamic balance of the shoulder and prevents the humeral head from moving out of the glenoid.

When these structures are damaged, the joint loses its natural balance. Ligament rupture, damage to the labrum or muscle weakness can cause the humerus to move abnormally, increasing the risk of dislocation.

People with shoulder instability may experience a variety of symptoms. A patient suffering from shoulder instability often describes a feeling of joint looseness, as if the shoulder were ‘popping out of its socket’. This phenomenon may occur suddenly, during a specific movement, or may develop gradually. Pain often accompanies these episodes, particularly during movements requiring rotation or elevation of the arm.
For some, the instability manifests itself in repeated dislocations, sometimes requiring emergency reduction. For others, the discomfort is more insidious. A simple tightening of the arm may trigger marked apprehension, forcing the patient to avoid certain movements for fear of dislocating the shoulder. Decreased muscle strength and limited mobility are also frequent signs of damage to the stabilising structures.

In chronic cases, repeated episodes of dislocation can lead to secondary complications, such as bone or cartilage lesions. A Bankart lesion, corresponding to a tear in the anteroinferior labrum, or a Hill-Sachs lesion, impacting the humeral head, are often associated with this condition.

Shoulder instability can be caused by a number of different mechanisms. Acute trauma, particularly violent shocks sustained in an accident or fall, is a frequent cause. Initial dislocation often results in damage to the stabilising structures, increasing the risk of recurrence. Similarly, contact sports such as rugby increase the risk of violent shocks that can lead to dislocation. Other cases occur progressively as a result of repeated microtrauma, often observed in sportspeople practising disciplines involving overhead movements such as swimming, handball or volleyball. Some individuals also have congenital ligament laxity, which favours subluxation even in the absence of apparent trauma.

Finally, multidirectional instability is a rarer form of the condition. Unlike unidirectional traumatic dislocation, which mainly affects the front of the shoulder, this instability affects several axes of movement. It often occurs in patients with generalised ligament laxity, affecting all the joints in the body.

Shoulder instability does not affect everyone in the same way. Several factors increase the risk of developing this condition. The first determining factor is a history of dislocation or severe trauma, especially if not properly treated, which significantly increases the risk of recurrence. Ligament laxity, often of constitutional origin, can affect several joints in the body, making the shoulder particularly mobile but less stable. Shoulder instability is more common in sportspeople exposed to repetitive, intense movements, particularly rugby, tennis and gymnastics.

Assessment of shoulder instability is based on a thorough clinical examination. The doctor carries out several tests to assess the mobility and stability of the joint. X-rays are used to identify any bone lesions, while MRI or arthroscanner scans are preferred to assess the state of the ligamentous and capsular structures.

The choice of treatment depends on the severity of the instability and its impact on daily life. Initially, a conservative approach is preferred. This is based on a re-education programme designed to strengthen the shoulder's stabilising muscles, particularly the rotator cuff and periscapular muscles. This protocol often improves stability and limits recurrence.

If instability persists despite rehabilitation, surgery may be considered. There are two possible approaches to stabilising the shoulder, and the choice between them depends on a number of factors, including the extent of the damage and the patient's level of activity. The stabilisation technique may be anatomical, as in the Bankart procedure, or in the form of a bone block, as in the Latarjet procedure.

Arthroscopic stabilisation or the Bankart-Neer procedure

This procedure involves reinserting the labrum and tightening a ligament arthroscopically. To achieve this, two or three resorbable anchors are implanted in the glenoid. This procedure can also be combined with dynamic anterior stabilisation by transferring the long head of the biceps; or with filling, which consists of placing a tendon in a bone gap on the head of the humerus. 

Latarjet or bone block stabilisation

In Latarjet stabilisation, a fragment of bone from the scapula, known as the coracoid process, is removed and fixed with two screws to enlarge the joint surface without blocking the shoulder.

Post-operative rehabilitation plays an essential role in the success of the treatment. After a period of immobilisation, physiotherapy sessions and progressive exercises are introduced to restore mobility and muscle strength. A return to sporting activities is generally possible after several months, depending on the patient's progress and the type of surgery performed.

Read the brochure Stabilisation de l'épaule  

Untreated instability can lead to progressive degradation of the stabilising structures, increasing the risk of early osteoarthritis. Chronic pain and reduced mobility are also possible complications, which can have a significant impact on quality of life and sporting activities.

Finally, there are rare risks inherent in any surgical procedure, as well as potential complications specific to shoulder stabilisation.

Adopting certain measures can limit the risk of shoulder instability. Targeted muscle strengthening helps to maintain good joint stability, thereby reducing the risk of dislocation. It is also essential to adapt technical movements in high-risk sports and to avoid extreme movements that could put excessive strain on the joint.

It is recommended to consult a specialist as soon as the first signs of instability appear. A sensation of slipping or loosening of the joint, even without complete dislocation, should raise the alarm. Persistent pain or marked apprehension during certain movements may indicate damage to the stabilising structures. If a dislocation has occurred, prompt treatment is necessary to prevent secondary damage and possible long-term complications.

Hôpital de La Tour offers a specialized, multidisciplinary approach to treating shoulder instability, from diagnosis of the disorder to rehabilitation. The team, made up of orthopaedic surgeons, radiologists and physiotherapists, provides personalized care.

What are the main causes of shoulder instability?
It can result from acute trauma, repeated microtrauma or ligament hyperlaxity predisposing to dislocation.

What are the warning signs?
A sensation of dislocation, persistent pain, apprehension when moving the arm or repeated episodes of dislocation are suggestive signs. A reduction in muscle strength and a loss of mobility may also appear over time.

How is shoulder instability diagnosed?
It is based on a clinical examination and imaging tests (X-ray, MRI, arthroscanner) to identify associated lesions.

Is it possible to treat instability without surgery?
Yes, rehabilitation may be enough to stabilise the shoulder. Surgery is considered in cases of persistent instability.

What surgical techniques are available?
Arthroscopic surgery is preferred for repairing labrum lesions and re-tensioning the ligaments. In cases of significant bone loss, a bone block using the Latarjet technique can be performed to improve joint stability over the long term.

How long does recovery last after shoulder stabilisation surgery?
The duration of rehabilitation varies according to the surgical technique used and the patient's progress. Temporary immobilisation is often necessary, followed by progressive exercises to restore strength and mobility. A return to sporting activities can generally be envisaged after 3 months.