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Clinical guides

Shoulder Dislocation

Comprehensive guide to shoulder dislocation for medical students. Covers presentation, diagnosis, management, and complications. Essential for clerkship.

By Samuel Bonne · · 7 min read

High-Yield Summary

Most common large joint dislocation: Anterior dislocation accounts for >95%.

Mechanism: Typically forced abduction, external rotation, and extension (e.g., catching oneself after a fall).

Classic Presentation: Severe pain, arm held in slight abduction and external rotation, loss of normal shoulder contour (squared-off appearance).

Do Not Miss: Neurovascular injury (especially axillary nerve) and associated fractures (Hill-Sachs, Bankart).

Diagnosis: Clinical suspicion confirmed with X-rays (AP, Y-scapular, axillary views). Management: Prompt reduction, often requiring analgesia/sedation, followed by immobilization and early rehabilitation.

Recurrence: High in young, active individuals.

Definition / Overview

Shoulder dislocation occurs when the head of the humerus completely separates from the glenoid fossa of the scapula. It is the most common major joint dislocation in the body. While anterior dislocations are overwhelmingly frequent, posterior and inferior (luxatio erecta) dislocations can also occur.

Epidemiology

Most common major joint dislocation: accounts for approximately 50% of all major joint dislocations.

Age: Bimodal distribution, with peaks in young, active males (trauma-related) and older adults (falls).

Sex: More common in males.

Recurrence: High risk, especially in individuals under 30 years old (up to 90% in some series) after an initial traumatic anterior dislocation.

Pathophysiology

Glenohumeral Joint: This is a highly mobile, ball-and-socket joint, making it inherently less stable than other major joints.

Static Stabilizers: Glenoid labrum, joint capsule, glenohumeral ligaments.

Dynamic Stabilizers: Rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) and long head of biceps.

Anterior Dislocation (Most Common):

Mechanism: Typically a traumatic event involving forced abduction and external rotation of the arm (e.g., direct blow, fall on outstretched arm).

Pathology: Often involves disruption of the anterior capsule and labrum (Bankart lesion). Associated Injuries: Humeral head impaction fracture (Hill-Sachs lesion) on the posterior-superior aspect of the humeral head, occurring when it impacts the anterior rim of the glenoid during dislocation.

Posterior Dislocation (Rare):

Mechanism: Usually due to forceful internal rotation and adduction, direct blow to the anterior shoulder, or convulsive seizures/electric shock.

Pathology: Posterior capsular/labral injury, reverse Hill-Sachs (anterior humeral head defect), or lesser tuberosity avulsion.

Inferior Dislocation (Luxatio Erecta):

Mechanism: Hyperabduction forcing the humeral head inferiorly.

Clinical Presentation

History

  • Mechanism of injury: Critical to determine direction of dislocation.
    • Anterior dislocation: Often follows a FOOSH or trauma with the arm abducted and externally rotated.
    • Posterior dislocation: Classically associated with seizures or electrocution.
  • Pain: Severe, acute shoulder pain.
  • Inability to move arm: The patient often supports the injured arm.

Physical Exam

Inspection

  • Anterior dislocation:
    • Flattening or “squared-off” appearance of the deltoid
    • Prominent acromion
    • Humeral head may be palpable anteriorly in thin patients
    • Arm typically held in slight abduction and external rotation
  • Posterior dislocation:
    • Findings may be subtle
    • Arm held in adduction and internal rotation
    • Flattening of the anterior shoulder
    • Posterior prominence may be visible
  • Luxatio erecta:
    • Arm held in sustained abduction with the elbow flexed
    • Humeral head may be palpable inferiorly in the axilla

Palpation

  • Assess for tenderness, swelling, and bony deformity.

Neurovascular Exam

Critical in all suspected shoulder dislocations.

  • Motor:
    • Deltoid contraction: axillary nerve (C5-C6)
    • Wrist extension: radial nerve
    • Finger flexion/extension: median and ulnar nerves
  • Sensory:
    • Lateral deltoid: axillary nerve patch
    • First dorsal web space: radial nerve
    • Tip of index finger: median nerve
    • Tip of little finger: ulnar nerve
  • Vascular:
    • Check radial, ulnar, and brachial pulses
    • Assess capillary refill

Range of Motion

  • Severely limited and painful, especially with active movement.

If You See X, Think Y

  • If you see a patient after a seizure or electrocution with a painful, internally rotated shoulder, suspect a posterior shoulder dislocation.

Red Flags

  • Neurological deficit:
    • Especially axillary nerve palsy
    • Findings:
      • Weakness of the deltoid muscle
      • Sensory loss over the lateral shoulder (“regimental badge” area)
  • Vascular compromise:
    • Absent or diminished pulses
    • Pallor and coolness of the affected extremity
    • Suggests possible arterial injury → emergency
  • Open dislocation:
    • Skin breach over the dislocation site
    • High risk of infection → requires urgent management
  • Associated fractures:
    • Humeral head fracture (Hill-Sachs lesion)
    • Glenoid rim fracture (Bankart lesion)
    • These can complicate reduction and increase recurrence risk
  • Inability to reduce:
    • May indicate:
      • Soft tissue interposition (e.g., labrum, capsule)
      • Significant associated fracture
    • Requires urgent orthopedic evaluation

Diagnosis

Clinical

  • Strongly suspected based on history and physical exam.

Imaging

Essential to:

  • Confirm the diagnosis
  • Determine direction of dislocation
  • Identify associated fractures
  • Assess for underlying pathology

X-rays (REQUIRED)

AP View

  • Evaluates position of the humeral head relative to the glenoid
  • Anterior dislocation: Humeral head appears inferior and medial to the glenoid
  • Posterior dislocation: May show the classic “light bulb” sign
    • Internally rotated humeral head
    • Loss of normal anterior convexity

Y-Scapular View

  • Best view to determine direction of dislocation
  • Anterior dislocation: Humeral head lies anterior to the “Y”
  • Posterior dislocation: Humeral head lies posterior to the “Y”

Axillary View (or Velpeau view if unable to abduct)

  • Critical view
  • Clearly shows relationship between humeral head and glenoid
  • Helps detect:
    • Glenoid rim fractures
    • Direction of dislocation

CT Scan

  • Indicated when:
    • X-rays are equivocal
    • Suspected complex fractures (e.g., glenoid rim, Hill-Sachs lesion)
    • Concern for loose bodies

MRI

  • Not typically required acutely
  • Useful for evaluating soft tissue injuries, including:
    • Labral tears
    • Capsular injuries
    • Rotator cuff pathology
  • Consider in recurrent dislocations or persistent post-reduction pain

Management

Immediate Goals

  • Provide pain relief
  • Perform prompt reduction
  • Conduct thorough neurovascular assessment

Pain Control

  • Oral analgesics: NSAIDs, acetaminophen
  • Stronger pain: Systemic opioids if needed

Sedation / Muscle Relaxation

  • Often required for successful reduction
  • Typically done via procedural sedation in the ED

Reduction Techniques (Anterior Dislocations)

  • Traction-Countertraction (most common):
    • Gentle traction on the arm
    • Assistant provides counter-traction to the torso
  • Stimson Technique:
    • Patient prone with arm hanging off table
    • Weight applied to wrist for gradual reduction
  • Kocher’s Method:
    • Stepwise: external rotation → adduction → internal rotation
    • ⚠️ Use caution: Risk of iatrogenic fracture if forceful
  • Scapular Manipulation:
    • Arm stabilized while pressure applied to inferior scapula
    • Often effective and less painful

Post-Reduction Care

Neurovascular Reassessment

  • Immediately after reduction
  • Compare with pre-reduction findings

Post-Reduction X-rays

  • Confirm successful reduction
  • Rule out iatrogenic fractures

Immobilization

  • Sling for comfort and protection
  • Typical duration: 1-3 weeks
    • Depends on age, activity level, associated injuries
  • External rotation bracing:
    • Historically used
    • Current evidence is uncertain vs. standard sling

Rehabilitation

  • Begin early mobilization when safe
  • Progress to strengthening:
    • Rotator cuff
    • Scapular stabilizers
  • Goal: restore ROM and prevent recurrence
  • Physical therapy referral is essential

Orthopedic Consultation (Indications)

  • Associated fractures:
    • Displaced greater tuberosity
    • Significant glenoid fracture
  • Irreducible dislocation
  • Neurovascular injury
  • Recurrent dislocations (consider surgical stabilization)
  • First-time dislocation in young/athletic patients with high recurrence risk

Complications

Neurovascular Injury

  • Most common: Axillary nerve injury (up to 40% of anterior dislocations)
    • Typically transient
  • Less common: Brachial plexus injury
  • Rare but serious: Axillary artery injury → limb-threatening

Rotator Cuff Tears

  • More common in patients >40 years old
  • Often associated with greater tuberosity fractures

Fractures

  • Hill-Sachs lesion:
    • Posterolateral humeral head impaction fracture
  • Bankart lesion:
    • Avulsion of the anterior-inferior labrum
  • Bony Bankart lesion:
    • Avulsion of the glenoid bone
  • Greater tuberosity fracture

Recurrent Dislocation

  • Common in young, active individuals
  • May require surgical stabilization (e.g., Bankart repair)

Instability

  • Chronic sensation of the shoulder “giving way”
  • Often follows repeated dislocations

Rotator Cuff Arthropathy

  • Long-term complication
  • Results from chronic instability + rotator cuff deficiency

Adhesive Capsulitis (Frozen Shoulder)

  • More common in older patients
  • Associated with prolonged immobilization

Differential Diagnosis

  • Rotator cuff tear:
    • Especially acute traumatic tears
    • Patient can often initiate some movement
    • Pain tends to localize differently than dislocation
  • Proximal humeral fracture:
    • Severe pain and deformity after trauma
    • Humeral head remains in the glenoid (no true dislocation)
  • Acromioclavicular (AC) joint separation:
    • Pain localized to the AC joint
    • Visible step-off deformity
    • Normal glenohumeral alignment
  • Glenohumeral subluxation:
    • Partial dislocation
    • May reduce spontaneously
    • Can present as chronic instability
  • Clavicle fracture:
    • Pain and tenderness over the clavicle
    • Often visible deformity or displacement
  • Shoulder contusion / sprain:
    • Less severe pain
    • Typically preserved range of motion

Exam Pearls

If You See X, Think Y

  • Anterior dislocation:
    • Arm held in slight abduction and external rotation
  • Posterior dislocation:
    • Arm held in adduction and internal rotation

→ This positioning is a key diagnostic clue

Do Not Miss

  • Always perform and document a neurovascular exam BEFORE and AFTER reduction
  • Axillary nerve is the most commonly injured
    • Check deltoid function and lateral shoulder sensation

Classic Presentation

  • Young male athlete
  • Mechanism: fall on an outstretched, abducted, externally rotated arm
  • Findings:
    • “Squared-off” shoulder
    • Refuses to move the arm

→ Assume anterior shoulder dislocation until proven otherwise

Palpation Clues

  • Anterior dislocation:
    • Humeral head may be felt anteriorly (beneath the coracoid process)
  • Posterior dislocation:
    • Anterior shoulder feels “empty”

Common Traps / Pitfalls

  • Missing a neurovascular injury:
    • Rushing to reduction without a proper pre-reduction neurovascular exam
    • Risk:
      • Missing baseline deficits
      • Misattributing post-reduction deficits
  • Inadequate imaging:
    • Failure to obtain appropriate views (e.g., axillary view, Y-scapular view)
    • Can lead to:
      • Missed posterior dislocations
      • Missed associated fractures
  • Forceful reduction:
    • Excessive force increases risk of:
      • Iatrogenic fractures (e.g., greater tuberosity)
      • Additional soft tissue injury
  • Missing a posterior dislocation:
    • Often subtle on AP X-ray
      • “Light bulb” sign may be overlooked
    • Frequently only identified on:
      • Axillary or lateral views
    • High-risk scenarios: seizures, electrocution
  • Inadequate post-reduction care:
    • Poor immobilization or lack of rehabilitation
    • Leads to:
      • Recurrent dislocations
      • Chronic instability

FAQ

Q: What is the most common type of shoulder dislocation?

  • A: Anterior shoulder dislocation
  • Accounts for >95% of cases

Q: Why is it important to perform a neurovascular exam before reduction?

  • A: To:
    • Document any pre-existing nerve or vascular injury
    • Ensure no new injury occurs during reduction
  • Especially important for the axillary nerve

Q: How long should the shoulder be immobilized after a first-time dislocation?

  • A: Variable and debated
  • Typical approach:
    • 1-3 weeks in a sling for comfort
    • Followed by early mobilization + physiotherapy
  • Longer immobilization:
    • May increase stiffness
    • Does not reduce recurrence (no benefit shown beyond 1 week in a sling)

Q: What is a Hill-Sachs lesion?

  • A:
    • Impaction fracture of the posterior-superior humeral head
    • Occurs when the humeral head impacts the anterior-inferior glenoid rim during an anterior dislocation
  • Indicates significant bony trauma

Q: What is the risk of recurrence?

  • A:
    • High in young, active individuals (up to ~90% in some groups)
    • Decreases with age
    • Influenced by:
      • Activity level
      • Type of sport
      • Degree of initial injury

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