Shoulder Instability and Dislocations

Shoulder Instability and Shoulder Dislocations

The stability of the glenohumeral (shoulder) joint is provided by both soft tissue (the labrum) and muscles (rotator cuff) to result in both static and dynamic stability. Instability is most common in adolescent and young adult athletes, with the most common instability events occurring traumatically. Anterior (forward) dislocations of the shoulder may occur during overhead sports with or without contact. 

Instability comprises 23% of all shoulder injuries among NCAA athletes. While the vast majority are anterior, about 10% of dislocations occur posteriorly (out of the back). Approximately 85% of traumatic anterior injuries do not require reduction (putting back into place) and are simply a subluxation or incomplete instability event. 

Acute, Traumatic Shoulder Instability

The humeral head (ball) is maintained in the glenoid (socket) throughout shoulder range of motion. The aforementioned soft tissue (static) restraints include the anterior band of the inferior glenohumeral ligament (IGHL), the middle glenohumeral ligament (MGHL) and the superior glenohumeral ligament (SGHL); each of which contribute as a restraint to anterior translation at different positions of shoulder abduction. 

Bankart Lesions

A Bankart lesion is an avulsion of the anterior labrum and anterior band of the IGHL from the anterior inferior glenoid and is present in 80-90% of patients with traumatic anterior shoulder instability (TUBS). In the case of a “bony” Bankart Lesion, the glenoid rim is also involved.

Hill-Sachs Lesions

When the humeral head dislocated anteriorly, the backside of the humeral head makes contact with the glenoid rim, resulting in an impression fracture of the posterosuperior humeral head known as a Hill-Sachs Lesion.

Natural History

The orthopaedic literature has demonstrated a high rate of recurrent dislocations in young, active athletes – greater than 90%. The rate of recurrence reduces with each decade after age 20 years. Individuals > 40 years old who sustain a dislocation are more likely to tear their rotator cuff or fracture their greater tuberosity during a shoulder dislocation.

Physical Examination and Work-Up

Our physicians will assess range of motion, strength and tolerance for “apprehension” positions during your exam. Positions of apprehension, such as the “high five” position, may be provocative in individuals with anterior shoulder instability. 

Shoulder Clinical Instability Tests

Anterior Load and Shift: this clinical test assesses for laxity of the glenohumeral joint. The patient lies supine and the examiner holds the patient’s scapular with one hand, while grasping the patient’s upper arm with the other. The examiner translates the humeral head anteriorly. 

Posterior Load and Shift: this clinical test assesses for laxity of the glenohumeral joint. The patient lies supine and the examiner holds the patient’s scapular with one hand, while grasping the patient’s upper arm with the other. The examiner translates the humeral head posteriorly. 

Grading of Translation of the Humeral Head

1+: translation to glenoid rim

2+: translation over glenoid rim, but reduces

3+: translates and locks out of glenoid

Apprehension and Relocation: this clinical test assesses the patient’s sensation of instability. The patient begins supine. The arm is abducted to 90 degrees and placed into full external rotation. Patients may express apprehension or a feeling of instability. The Relocation test is performed by the examiner placing their hand on the humeral head and applying a posterior directed force, which will result in the patient experiencing an elimination of the sensation of instability by the patient.

Sulcus Sign: this clinical test assesses for the presence of multidirectional instability (MDI). The patient stands or sits with their arms at their side. The affected arm is pull inferiorly and the examiner looks to see if a sulcus forms at the superior aspect of the humeral head. 

Sulcus Grading:

1+: acromiohumeral interval < 1 cm

2+: acromiohumeral interval 1-2 cm

3+: acromiohumeral interval > 2 cm

Radiology

X-rays assess for bony injury, as with Bankart and Hill-Sachs lesions. An MRI or MRA (magnetic resonance arthrograpthy) is performed to delineate tearing of the labrum, as well as any other concurrent injuries to the rotator cuff or biceps tendon. Occasionally, if there is damage to the glenoid suspected, a CT scan will be ordered.

Treatment

First time dislocations are often treated with physical therapy, activity modification and short-term immobilization. Physical therapy focuses on regaining motion, strengthening of the shoulder girdle musculature, and neuromuscular/proprioceptive training. 

An Arthroscopic Bankart Repair with or without a capsular shift is indicated in first-time traumatic shoulder dislocations in athletes younger than 25 years of age, high demand athletes, those who suffer recurrent dislocation/subluxations following failed non-operative management, and/or <20% glenoid bone loss. The purpose of surgical management is to restore the stability of the glenohumeral joint by repairing the labrum and possibly the glenohumeral ligaments. Arthroscopic Bankart repair is common as it permits excellent visualization of the entire joint, however, open procedures are sometimes necessary if an extensive glenoid/bony injury has occurred. 

Post Op Rehabilitation

Following Bankart Repair, the operative shoulder is protected in a sling for sling for 4-6 weeks depending on the extent of injury. Light exercises of the elbow, wrist and hand are started immediately following surgery. After initial immobilization, a therapist helps restore full range of motion of the shoulder, then progresses strengthening. Throughout the rehabilitation progression, assessments will be performed in the COSMO Fit Lab to provide an individualized, criterion-based progression of the rehabilitation protocol and will be shared with your therapist.