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Shoulder Instability

Overview

Shoulder instability refers to symptoms in which a patient experiences an unstable shoulder joint, often accompanied by increased laxity in specific directions. In the realm of shoulder injuries, two key concepts arise: micro-instability and major forms of instability such as subluxation and dislocation.

Micro-instability

Micro-instability describes the pathological motion of the humeral head, frequently occurring in multiple directions due to generalized capsular laxity. This condition does not align often with a specific traumatic event but rather emerges progressively.

Subluxation and Dislocation

Subluxation

Subluxation involves translating the humeral head beyond its normal physiological limits while maintaining contact with the glenoid. It indicates a partial dislocation, where functionality is momentarily compromised but remains intact.

Dislocation

Conversely, dislocation occurs when the translation of the humeral head is significant enough to disconnect entirely the articular surfaces of the humerus and the glenoid. This level of instability typically necessitates manual reduction to restore proper alignment.

Types of Instability

Anterior Instability

Anterior instability is the most common form, manifesting in over 90% of shoulder dislocations. This condition arises from a single traumatic episode, typically involving abduction and external rotation (ABD and ER) of the shoulder.

Posterior Instability

Less frequent than anterior instability, posterior instability accounts for only 2% to 10% of shoulder dislocations. It is commonly associated with posterior dislocations linked to axial loads applied to an adducted arm, often noted in trauma cases such as electrocution or seizures.

Multidirectional Instability (MDI)

Multidirectional instability does not necessarily follow a traumatic incident and is characterized by congenital or acquired capsular ligamentous laxity. This type can result from connective tissue disorders or repeated minor injuries to the capsuloligamentous complex, showing abnormal humeral head translation in multiple directions. Symptoms may include recurrent subluxations or dislocations with minimal stress and display signs of general ligamentous laxity, such as hyperextension of fingers and elbows.

Classification of Instabilities

  • TUBS: Traumatic unidirectional instability associated with a Bankart lesion, typically requiring surgery.

  • AIOS: Acquired Instability due to Overstress Syndrome.

  • AMBRI: Atraumatic multidirectional instability with bilateral laxity, emphasizing rehabilitation as the primary treatment, though inferior capsular shift surgery may be indicated if unsuccessful.

Assessment History

Clinical assessment of shoulder instability should begin with a thorough history encompassing:

  • Age and duration of symptoms.

  • Trauma events and associated pain levels.

  • Involvement in sports, particularly throwing or overhead activities.

  • Experiences with voluntary subluxation or indications of clunk or knock.

  • Patient limitations in movement due to fear or previous dislocations and subluxations.

Tests and Measures

  • Active Range of Motion (AROM): This may be painful.

  • Passive Range of Motion (PROM): Could show excessive motion and apprehension at extremes.

  • Accessory motions: May indicate greater excursion or potential subluxation.

Instability Tests

Important tests for assessing shoulder instability include:

  • Apprehension and relocation test

  • Load and shift test

  • Sulcus sign

  • B relocation component

Rehabilitation Considerations

Factors Influencing Rehabilitation

Factors impacting rehabilitation strategies include:

  • Onset of pathology

  • Degree and direction of instability

  • Frequency of dislocations

  • Any associated pathologies

  • Neuromuscular control

  • Activity levels of the patient

Traumatic Shoulder Instability (TUBS)

Traumatic shoulder instability is prominently observed in acute dislocations of the glenohumeral joint, frequently seen in sports injuries. Identifying the specific site of damage becomes crucial; using a clock-face analogy allows clinicians to describe glenoid damage accurately, with hours indicating respective anterior and posterior locations.

Bankart Lesion

Bankart lesions typically occur due to anterior shoulder dislocations, damaging the anterior inferior glenoid labrum, which can lead to the formation of a pocket that facilitates the dislocation of the humeral head, termed a fibrous Bankart lesion. A bony Bankart lesion includes an associated fracture of the anterior-inferior glenoid cavity.

SLAP Lesion

A SLAP lesion entails injury to the superior glenoid labrum characterized as a superior labral tear from anterior to posterior, often resulting from trauma or repetitive stress, such as throwing.

Examination and Management

The acute management of dislocations includes:

  • Obtaining x-rays to rule out fractures before reduction.

  • Reducing the dislocation as promptly as possible, with post-reduction imaging recommended.

Rehabilitation Phases

  • Phase I - Acute Phase:

    • Focus on pain reduction and prevention of muscle wasting.

    • Self-limiting positioning with controlled immobilization practices.

  • Phase II - Intermediate Phase:

    • Emphasizing full range of motion recovery, strengthening, and re-establishing muscular balance.

  • Phase III - Advanced Strengthening:

    • Gradual return to unrestricted activities with enhanced strength and stability.

Conclusion

Understanding the nature of shoulder instability along with appropriate rehabilitation strategies is crucial for effective recovery and restoration of shoulder function. Tailoring programs based on individual patient profiles, injury types, and specific rehabilitation phases pave the way for optimal recovery outcomes.