Shoulder Dislocation

Glenohumeral dislocation is displacement of the humeral head from the glenoid.

The shoulder has the greatest range of motion of any major joint and consequently depends heavily on:

• Labrum
• Capsule
• Glenohumeral ligaments
• Rotator cuff
• Dynamic muscular control

for stability.

Direction classification

Anterior

More than 90% of shoulder dislocations.

Usually caused by abduction, extension and external rotation.

Subtypes according to final humeral head position include:

• Subcoracoid, commonest
• Subglenoid
• Subclavicular
• Rare intrathoracic dislocation

Posterior

Usually caused by:

• Seizure
• Electric shock
• Direct trauma

The arm is typically held adducted and internally rotated.

Inferior

Luxatio erecta.

The humeral head lies inferior to the glenoid and the arm is fixed overhead in abduction.

It is associated with a high rate of neurovascular and rotator cuff injury.

Associated lesions in anterior instability

Bankart lesion

Detachment of the anteroinferior labrum from the glenoid.

Bony Bankart

Anteroinferior glenoid rim fracture associated with the labral injury.

ALPSA lesion

Anterior labroligamentous periosteal sleeve avulsion, where the labrum and periosteum displace medially and heal abnormally on the glenoid neck.

HAGL lesion

Humeral avulsion of the inferior glenohumeral ligament.

Hill Sachs lesion

Posterolateral humeral head impaction caused by collision with the anterior glenoid rim.

Posterior instability lesions

Reverse Bankart

Posterior labral avulsion.

Reverse Hill Sachs

Anteromedial humeral head impaction caused by the posterior glenoid during posterior dislocation.

Glenoid track classification

Bipolar bone loss should be assessed as a combined humeral and glenoid problem.

Approximate glenoid track width:

0.83 × intact glenoid diameter minus anterior glenoid bone loss

The Hill Sachs interval includes:

• Width of Hill Sachs defect
• Bone bridge between the lesion and rotator cuff insertion

On track lesion

Hill Sachs interval remains within the glenoid track.

Lower engagement risk.

Off track lesion

Hill Sachs interval extends beyond the glenoid track.

Higher risk of engagement and recurrent instability after soft tissue repair alone.

Anterior dislocation

Arm held:

• Slightly abducted
• Externally rotated

Loss of normal rounded shoulder contour is present.

The humeral head may be palpable anteriorly.

Posterior dislocation

Arm is:

• Adducted
• Internally rotated

The patient cannot externally rotate the arm.

Bilateral posterior dislocations should raise suspicion for seizure or electric injury.

Inferior dislocation

Arm is fixed overhead.

Neurological injury is common.

Neurovascular assessment

Document axillary nerve function before and after reduction:

• Sensation over lateral deltoid
• Deltoid motor function when feasible

Also document:

• Musculocutaneous nerve
• Radial nerve
• Median nerve
• Ulnar nerve
• Radial pulse

Axillary nerve neuropraxia is the most common nerve injury.

Older patients should be examined carefully for rotator cuff tear after reduction.

Obtain:

• AP shoulder
• Scapular Y
• Axillary lateral

A posterior dislocation is easily missed on AP radiographs. The axillary view is particularly important.

If the patient cannot abduct sufficiently for a conventional axillary image, use a modified axillary or Velpeau view.

CT is useful for:

• Glenoid bone loss
• Greater tuberosity fracture
• Proximal humeral fracture
• Locked posterior dislocation
• Large Hill Sachs lesion
• Surgical planning

MRI or MR arthrography is useful for:

• Labral injury
• HAGL
• Rotator cuff tear
• Recurrent instability

Acute reduction

Provide adequate analgesia and muscle relaxation.

Options include:

• Procedural sedation
• Regional anaesthesia
• Intra articular local anaesthesia

A practical intra articular option is approximately:

Lidocaine 1%, 10 to 20 mL, provided the total safe local anaesthetic dose is respected.

Reduction techniques for anterior dislocation include:

• Scapular manipulation
• External rotation method
• Milch technique
• Traction countertraction
• Cunningham technique

Avoid forceful leverage against the humerus because this can produce fracture, particularly in older patients.

If fracture is suspected, obtain radiographs before forceful manipulation.

After reduction:

• Confirm clinically and radiographically
• Repeat axillary nerve examination
• Repeat vascular examination

First anterior dislocation

Immobilise briefly for comfort, then begin progressive range of motion.

Prolonged immobilisation does not reliably prevent recurrence.

The recurrence risk is greatest in:

• Young patients
• Male patients
• Contact athletes
• Patients with substantial bone loss
• Patients with hyperlaxity
• Off track Hill Sachs lesions

In a young high risk contact athlete, surgical stabilisation can reasonably be offered even after a first traumatic dislocation because recurrence after nonoperative treatment is high.

Arthroscopic Bankart repair

Appropriate for recurrent traumatic anterior instability with:

• Bankart lesion
• Minimal glenoid bone loss
• On track Hill Sachs lesion

Repair the labrum and restore capsulolabral tension.

Bankart plus remplissage

Useful for an off track or engaging Hill Sachs lesion when glenoid bone loss is limited.

The posterior capsule and infraspinatus are fixed into the Hill Sachs defect, converting the defect into an extra articular lesion and preventing engagement.

Potential tradeoff is a small loss of external rotation.

Glenoid bone loss

Significant anterior glenoid loss increases failure of isolated Bankart repair.

Historically approximately 20% to 25% loss has been considered critical, although contemporary data show that even smaller, subcritical defects can increase recurrence in high demand patients.

Substantial glenoid deficiency is treated with bony augmentation, commonly:

Latarjet procedure

The coracoid with conjoint tendon is transferred to the anterior glenoid.

It provides:

• Bony restoration
• Sling effect from conjoint tendon
• Capsular reinforcement

Other options include distal tibial allograft or iliac crest graft in selected revision or major bone loss cases.

Posterior dislocation

Reduce acute uncomplicated posterior dislocation carefully.

A locked posterior dislocation associated with a large reverse Hill Sachs defect may require surgery.

Treatment depends on defect size and duration.

Options include:

• Lesser tuberosity transfer into the defect, modified McLaughlin procedure
• Bone graft reconstruction
• Arthroplasty for massive head destruction or chronic unreconstructible injury

Inferior dislocation

Reduce urgently with adequate sedation.

Perform particularly careful neurovascular reassessment because axillary nerve and brachial plexus injury are frequent.

Rehabilitation

After uncomplicated reduction:

• Short sling period
• Early assisted movement
• Progressive rotator cuff strengthening
• Scapular stabilisation

Return to contact sport only after:

• Full painless range
• Near symmetric strength
• No apprehension or instability

Major complications include:

• Recurrent instability
• Axillary nerve injury
• Rotator cuff tear
• Bankart lesion
• Hill Sachs lesion
• Glenoid bone loss
• Post instability arthropathy
• Stiffness after prolonged immobilisation