Traumatic Anterior Shoulder Instability

Being the most mobile joint in the body is a huge responsibility indeed. This means that the stability of the shoulder is often the first thing that gets sacrificed when a traumatic injury occurs. Another daunting fact is that once a shoulder dislocation or instability episode happens the rate of recurrence in later years is at least 70%.

Traumatic instability (TUBS) is instability that happens from a force that is large enough to injure some of the major supporting structures of the joint like the glenohumeral capsule, ligaments, rotator cuff, or the bone of the humerus or glenoid. Anterior glenohumeral instability is the shoulder condition in which soft-tissue or bony injury allows the humeral head to subluxate or dislocate from the glenoid fossa and the joint surfaces no longer touch each other.

Traumatic anterior shoulder instability (TASI) accounts for 95% of glenohumeral dislocations so this just shows how common this type of instability is. When this takes place due to a traumatic event, the function of the shoulder most likely compromised. The patient will usually go through apprehension, recurrent subluxations, and frank dislocations. Following these mechanisms certain activities including overhead arm motions, external rotation, and, thus, physical or athletic activities will be hugely limited.

As per the Stanmore triangle of instability there are three classifications which are Traumatic structural, Atraumatic structural and the Habitual non-structural (muscle patterning or neurological changes). A traumatic instability can occur as a result of a fall on the outstretched hand during a sports activity like football, or wrestling.

A careful history and clinical examination and diagnostic X-rays are often helpful in evaluating the patient with traumatic instability. There are specifically designed physical tests for this as well like the apprehension, relocation and surprise (release) test. These tests are highly specific and strongly predictive of traumatic anterior glenohumeral instability. A fourth test, the bony apprehension test diagnose can especially help diagnose instability with a significant osseous lesion component. A detailed MRI following the tests can help reveal labrum or bony injuries of the glenoid and proximal humerus which is a condition called Hill Sachs.

Some common symptoms related to recurrent anterior instability could be glenohumeral joint pain, shoulder stiffness with difficulty warming up for the activity, rotator cuff weakness, sensation of popping, grinding or catching deep in the shoulder joint, pain when reaching backward or above shoulder height, apprehension when sleeping with the arm overhead in abduction and external rotation. The resultant neurological symptoms can be tingling or burning in the lower arm and hand or a localized numbness of the skin overlying the deltoid muscle and also tenderness of the anterior glenohumeral joint line and the posterior rotator cuff.

Depending on chronicity of symptoms, recurrence of instability, and the severity of labrum or glenoid defects, the treatment options can be operative or non-operative. Non-operative treatments include slings, bracing and physiotherapy. Operative treatment can include bony and soft-tissue reconstructions performed through open or arthroscopic approaches. Arthroscopic Bankart is the most common surgical procedure for the treatment of anterior shoulder instability. The modified Latarjet procedure have also been fairly successful in those with combined bone loss.

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