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Coordination of joint alignment is a complex process involving the nervous and muscular systems. Abnormalities of any of the components (the shape of the bone, the articular rim, the joint capsule with ligaments and the muscles surrounding the joint) can lead to instability of the shoulder joint.
Symptoms of shoulder instability
- pain and weakness are the most commonly experienced symptoms,
- fear of performing certain movements,
- sensation of instability, subluxation of the joint,
- pain during shoulder movement imitating throwing,
- recurrent dislocations,
- painful symptoms when performing movements in certain planes,
- jumping of the joint with a characteristic "click".
Shoulder instability - causes
The most common cause of shoulder instability is trauma. It is a consequence of the head of the humerus falling out of the acetabulum of the joint, accompanied by damage to the collarbone, ligaments, and often bone damage in the form of a fracture of the acetabulum of the scapula and the head of the humerus. These tissues can also be overloaded when we practice sports that require dynamic work with the shoulder positioned in abduction and external rotation, such as frequently throwing a ball, dynamically serving a ball in volleyball or tennis, as well as with numerous injuries in contact sports. The first dislocation can lead to further dislocations, followed by a sense of instability.
A completely different type of shoulder instability is instability resulting from congenital flaccidity of the connective tissue. Such instability is not the result of mechanical damage to the stabilizing structures of the shoulder as a result of trauma, but their genetically determined excessive elasticity.
Directions of shoulder instability
- Anterior instability - the most common,
- Posterior instability - is a rarer form of instability and usually occurs due to sports injury,
- Multidirectional instability - results from multiple dislocations, and more often from congenital flaccidity.
Diagnosis of shoulder instability
Diagnosis of shoulder instability begins with a medical history and physical examination. The orthopedist checks range of motion, muscle strength, tissue flaccidity, and performs specific tests.
To get more detailed information, confirm the diagnosis and identify any additional problems, the doctor may order additional imaging tests: an X-ray (shows injuries to the bones that make up the shoulder joint) and an MRI (helps identify injuries to the ligaments and tendons surrounding the shoulder joint). To better visualize the problem of shoulder instability, the MRI is performed with the administration of contrast.
Shoulder instability - non-operative treatment.
An indication for non-operative treatment may be instability on non-traumatic grounds, i.e. joint limpness. Flaccidity is increased mobility in a joint that does not necessarily give pain. The group of non-traumatic instability includes cases of developmental abnormalities of the shape of the articular surfaces and cases of connective tissue disease. Pain in the shoulder is mainly caused by inflammation of the tendons responsible for stabilizing the head of the humerus during physical activity.
Instability, the cause of which is not trauma, can also be treated nonoperatively. This treatment consists of patient education, modification of physical activity and rehabilitation. Intensive exercises that reproduce normal movement patterns, strengthening the muscles of the shoulder girdle and centering the head of the humerus are the basis of treatment and produce satisfactory results.
Shoulder instability - surgical treatment
The most common cause of shoulder instability is trauma, specifically dislocation of the shoulder joint. In 90-95% of cases, this is an anterior dislocation, which occurs during impact when the limb is in a position of abduction and external rotation. Traumatic dislocation can result in additional bony injuries to the shoulder joint: a Bankart fracture - a fracture of the anteroinferior portion of the acetabulum, and a Hill-Sachs fracture - a compression fracture of the posterolateral surface of the humeral head.
A much rarer injury is a posterior dislocation, which can result from stretching or detachment of the posterior portion of the joint capsule and casing from the acetabulum of the scapula. Dislocations of this type are more difficult to diagnose.
Currently, mainly two types of surgical procedures are performed on patients with shoulder instability. Soft tissue procedures are aimed at reconstructing the rim and capsular complex. Bone tissue procedures are aimed at reconstructing the acetabulum of the shoulder joint. After surgery, the operated limb is immobilized in an orthosis. After about 12 weeks of rehabilitation, patients regain significant dexterity and can already perform gentle strength exercises.
Prognosis in shoulder joint instability
In cases of traumatic instability treated nonoperatively, the risk of recurrent dislocation is high. If symptoms of instability persist, surgery should be considered. After surgical treatment and completed rehabilitation, patients' prognosis is good. The increased risk of recurrence is mainly seen in contact sports players.
Instability of the shoulder joint - prevention.
Our lifestyle significantly affects the risk of experiencing instability of the shoulder joint. To reduce the possibility of the condition, it is important to remember regular exercises to strengthen the muscles around the joint, proper work ergonomics, and to distribute the weight over both shoulders.
Related articles:
Learn about other possible shoulder injuries and contusions.
Bibliography:
- OrthoInfo - Chronic Shoulder Instability - George S. Athwal, MD, Peer-Reviewed by Thomas Ward Throckmorton, MD, FAAOS - August 2021
- The Open Orhopeadics Journal - Anatomy and Biomechanics of the Unstable Shoulder - Ricardo Cuéllar, Miguel Angel Ruiz-Ibán, Adrián Cuéllar - 2017
- National Library of Medicine - Anterior Shoulder Instability - Matthew Varacallo; Matthew A. Musto; Scott D. Mair. - 2022
- Ortho Bullets - Traumatic Anterior Shoulder Instability (TUBS) - John Scanaliato MD, El Paso, Rachel Frank MD, CU Sports Medicine, Albert Lin MD, University of Pittsburgh Physicians, Department of Orthopaedic Surgery - American Shoulder and Elbow Surgeons - 2023
