Shoulder instability and labral tears
What is an unstable shoulder?
An unstable shoulder is a very loose joint, capable of losing joint congruence, that is, of moving away from the normal sliding joint area, which can sometimes dislocate, ie move or leave the site. If not properly treated, shoulder instability can progress to degenerative changes and osteoarthritis in the future.
The rotator cuff is responsible for a very important part of the glenohumeral stability, connecting the humerus to the scapula. It consists of tendinous tissue of four muscles: supraspinatus, infraspinatus, teres minor and subscapularis. The round head of the humerus articulates with the almost flat surface of the glenoid of the scapula. This surface is increased in area and made more concave by the presence of the labrum that surrounds the edge of the glenoid, giving it a cup shape more adapted to the convex spherical surface of the humeral head.
Surrounding the joint is the articular capsule, which acts as a sac with a small amount of synovial fluid that lubricates the joint, facilitating mobilities. The walls of this capsule are associated with ligaments - stringlike fibrous structures that also confer stability by connecting the glenoid directly to the humerus. The capsule allows a considerable amount of mobility, which is limited by the presence of the ligaments, such as a leash of a dog that reaches the end and prevents its progression.
Dislocations occur when a force exceeds the restraining force of the rotator cuff muscles and ligaments. Almost all dislocations are anterior, which means that the humerus moves forward out of the the glenoid. Only 3% of the dislocations are posterior.
Sometimes the shoulder does not dislocate completely and returns to its normal position; this condition is called subluxation.
Sometimes, even without total or parcial dislocation, a simple forced mobilization of umerus against glenoid and surrounding labrum may cause labral tears.
What causes an unstable shoulder?
Shoulder instability often occurs as a consequence of traumatic first shoulder dislocation. This initial lesion is usually very significant, requiring reduction of the shoulder, that is, joint manipulation to put the humeral head in congruence with the glenoid surface. In these situations, the shoulder may appear to be back to normal, but the joint may remain unstable, due to injury to the ligaments or labrum, which lose their function of limiting abnormal mobilities. An unstable shoulder can lead to repetitive dislocations, even during activities. Instability can also follow less severe shoulder injuries.
In some cases, instability may occur without dislocations. It may be present in people with frequent shoulder mobilizations that lead to repeated capsular distension, such as in some sports (volleyball, baseball, swimming). If the capsule becomes loose and muscles weak, instability occurs. Eventually this can cause shoulder pain and irritation.
Genetic problems can lead to laxity of the ligaments, that may not be effective in stabilizing the joints, particularly the shoulder, which can easily be dislocated.
In other situations, following forced and sudden shoulder mobilization, namely during throwing activities, similar labral lesions may occur, involving its superior part. These are the SLAP (superior labral from anterior to posterior) lesions, that may demand different surgical procedures, regarding superior labrum close relation to proximal byceps tendo injuries.
What are the symptoms of an unstable shoulder?
Chronic instability can cause various symptoms. Recurrent subluxation is one of them and occurs commonly when the hand is raised over the head in a throwing movement, for example. This subluxation causes a sudden sensation of pain, as if something is moving or pinching the shoulder. Over time, some people may fail to perform certain subluxation-causing movements.
The shoulder may become so loose that it begins to dislocate frequently and may be a real problem, particularly if the patient is unable to reposition the shoulder autonomously and has to go to an emergency department to do so.
The dislocation of the shoulder is usually very obvious, with important deformity of the shoulder associated with intense pain. In these cases, any attempt to mobilize the shoulder is very painful. Shoulder dislocation can be complicated by nerve damage in some cases, causing tingling or lack of sensitivity as well as muscle weakness of some muscles. These are usually transient situations, due to the distension of the nervous structures.
Whenever there was no complete or parcial dislocation, but there is a labral tear, pain may be less exuberant, without giving away sensation, presenting as catching or blocking, with lack of strength and loss of range of motion.
How is it diagnosed?
The doctor will make the diagnosis first through the medical history and physical examination. The medical history may include several questions about previous shoulder injuries, type of pain and how the symptoms are affecting the usual activities.
On physical examination and chronic instability without dislocation, the shoulder will be mobilized to test for strength and mobility and stress tests will be applied to the ligament structures in order to reproduce the sensation of instability or clamping that bothers the patient. Unless it is a very loose shoulder, these tests will not cause dislocation.
To confirm the diagnosis, radiographic examinations or even computed tomography and / or magnetic resonance imaging (usually with contrast), may be requested. Extreme conditions may require diagnostic arthroscopy. It is a surgical procedure that uses a small camera that enters the joint and allows the surgeon to explore and observe the anatomical structures of the shoulder and eventually identify the real causes of instability.
Is there non-surgical treatment?
The initial treatment to control pain is usually rest and anti-inflammatory medication. Although being a resource in specific situations, injections with steroids are not usually performed. Often these patients undergo a physiotherapy program. At the beginning patients are educated to avoid certain positions and activities that could put the shoulder at risk of injury or dislocation. Later, the focus will be on strengthening the rotator cuff muscles. There are other approaches, including applying ice or heat, massages and various types of exercises to improve mobility. This will increase shoulder stability and provide harmonious mobility. These treatments can take six to eight months.
And what are the surgical options?
If the rehabilitation program does not stabilize the shoulder, surgery may be necessary. There are many types of procedures to stabilize the shoulder, many of them performed by arthroscopy. The choice of the procedure will depend on the anatomical cause and severity of the instability as well as the characteristics of the patient. These procedures include:
- Bankar repair - It is the most common procedure performed in anterior shoulder instability and can be performed through arthroscopy with small incisions and the support of a camera that will allow the observation of the interior of the joint. The Bankart procedure consists of the suture of the part of the capsule and labrum, with the aid of suture anchors that allow its fixation to the bone.
- Capsule Plication - This is surgery is used to tension a lax or redundant capsule that may cause multidirectional instability.
- The Bristow-Latarjet procedure consists of the transfer of the end of the coracoid process (a bony prominence of the scapula) and a common tendon to the edge of the glenoid. This procedure is performed in situations where instability is severe and / or associated with anatomical changes of the glenoid. The arthroscopic approach has been described, which has not shown any advantages over the open procedure (requiring a small incision of 5cm), greatly increase the complexity of the procedure and the surgical time considerably.
- Reinserção do labrum superior (lesões SLAP) – whenever possible, SLAP tears are treated as a Bankart repair, consisting in labrum insertion. However, because of its close relation to long head of byceps (LHB), that may not be always possible and demand other procedures, particularly in LHB.
Rehabilitation after surgery — what to expect?
Rehabilitation after surgery is more complex. It will require the use of a forearm suspension to protect the shoulder for three to six weeks. The physiotherapists will guide the rehabilitation program depending on the surgical procedure.This program will take two to four months and complete recovery can occur only after six months.