Anterior shoulder instability

• Anterior shoulder instability occurs secondary to acute or chronic stretching of the anterior shoulder capsule, resulting in instability and decreased support over the anterior aspect of the glenohumeral joint. 
• It is seen following anterior shoulder dislocation and subluxation. 
• Causes:
  • repetitive and progressive stress on the anterior shoulder capsule from loading and stretching beyond functional range, as performed by swimmers and baseball/softball pitchers
  • incorrect technique and/or attempting to lift too heavy weights especially in the supine or semi-recumbent position in resistance trainers
• Shoulder dislocation can cause the humeral head to strike against the labrum, causing a labral injury (Bankart lesion) and a compression humeral head fracture (Hill-Sachs lesion).
  • Following an anterior dislocation, there is a 50% chance that it will reoccur again.
  • With repeated dislocations, there can be worsening Bankart and Hill-Sachs lesions, making relocation more difficult, and also predisposing to OA in the long term.
• Shoulder instability can cause rotator cuff tears.

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Presentation

• 95% of acute traumatic dislocations
  • Bankart lesions are the most common consequence of traumatic anterior shoulder instabilit
• Can be difficult to diagnose due to nonspecific signs and symptoms
• Pain may wake the patient at night when lying on the affected shoulder due to anterior slippage of the humoral head.

Signs and Symptoms

• Acute dislocations characterised by severe pain, loss of joint function, and loss of deltoid bulk.
• There may be paralysis or parasthesiae down the ipsilateral arm due to traction on the brachial plexus and axillary nerve.
• static : lack of alignment at rest position
• dynamic: lack of alignment during movement or weight-bearing
• Apprehension test may be positive.

Clinical assessment

• The Anterior release test
  • sensitivity of 91.9%
  • specificity of 88.9%
  • The patient is supine, the arm is abducted and externally rotated, the examiner’s hand closest to the patient applies a downward force over or close to the humeral head in an attempt to relocate and secure it within the glenoid. 
  • Once a firm pressure is applied the patient’s arm is externally rotated further at which stage the humeral head is suddenly released. The patient may experience pain, apprehension or a combination during the release phase of the test. 
  • Extreme caution is required because if the shoulder is very unstable, dislocation may occur during the release phase

Imaging

• For patients with first time dislocation, XR is recommended to confirm diagnosis (and also to confirm relocation), and exclude #/Bankart/Hill-Sachs.
• USS and MRI for rotator cuff disease if suspected

Management

Reduction of acute dislocation

• XR to exclude #
• Document neurovascular status
• Adequate analgesia and muscle relaxant
• Multiple reduction technique: none of them are superior than others:
  • Stimson technique: patient prone, with affected arm holding a 3-5kg weight for 15min.
  • Milch technique: patient supine or beach chair position, elbow flexed 90deg, arm is slowly maximally abducted whilst traction is applied.

Post initial reduction:

• Sling for 2 weeks
• Physiotherapy recommended for 6 weeks to restore strength and ROM
• Return to normal duties in 6-8 weeks

Reduction following recurrent dislocations:

• Less soft tissue damage: patient can often return to normal duties after 1-2 weeks.
• Patient should avoid positions where the elbow is above and posterior to the shoulder (eg cocking for throw, diving on outstretched hand)

When to refer:

• Any complex dislocations (eg with concurrent axillary nerve palsy)
• Early referral for elite athletes / military etc following first dislocation.
• Recurrent dislocations that is impacting on QOL.

Following surgery:

• 6 weeks of sling immobilisation
• Physiotherapy
• Return to contact sports ~6 months with brace

Physiotherapy

• depending upon the severity of injury, ROM and strength deficits, and the required activity demands of the patient.
• Refrain from activities and motion in extremes of ROM
• ROM exercises: Pendulum, rope and pulley
• Strengthening exercises: Isometric, flexion, abduction, extension
• Proprioception
• Active joint reposition drills for ER/IR