Shoulder dislocation

In shoulder dislocation, the head of the humerus dislocates completely or partially (subluxation) in one of three directions: anterior (most common), posterior, or inferior. Shoulder dislocation is usually the result of trauma, and, because the head of the humerus is substantially larger than the glenoid fossa, it is the most common type of joint dislocation. Typical symptoms include pain and restricted range of motion. Examination reveals a palpable dent in the shoulder caused by the empty glenoid fossa, while the head of the humerus may be palpable anterior or inferior to the glenoid fossa. X-rays of the shoulder in at least two views are necessary to rule out fractures and confirm the diagnosis. With adequate analgesia and muscle relaxation, the head of the humerus can be carefully repositioned into the glenoid fossa through various maneuvers. Reduction is followed by immobilization and subsequent rehabilitation. Patients with concomitant soft tissue lesions or recurrent shoulder dislocation may require surgery to stabilize the shoulder joint. Possible complications of shoulder dislocation include neurovascular damage (most commonly axillary nerve injury), continued instability, restricted range of motion, and rotator cuff injury.

For details on closed reduction techniques for anterior shoulder dislocations, see “Shoulder reduction.”

• Most common joint dislocation
• Sex: ♂ > ♀ [1]
• Peak incidence: 20–29 years of age [1]

Epidemiological data refers to the US, unless otherwise specified.

• Anatomy: The head of the humerus is larger than the shallow glenoid fossa, which accounts for the high incidence of shoulder dislocation.
• Trauma (e.g., falling on an outstretched arm): commonly associated with contact sports [1]
• Predisposing factors for recurrent shoulder dislocation
  • Rotator cuff tear
  • Damage to the glenohumeral ligament
  • Bankart lesion and Hill-Sachs lesion
  • Loose joint capsule
• For posterior dislocation: uncoordinated muscle contraction (e.g., seizure, electrical shock)

• Anterior shoulder dislocation: displacement of the humeral head anterior (and often also inferior) to the glenohumeral fossa (> 95% of cases) [2][3]
• Posterior shoulder dislocation: displacement of the humeral head posterior to the glenohumeral fossa (< 4% of cases) [4]
• Inferior shoulder dislocation: displacement of the humeral head inferior to the glenohumeral fossa (< 1% of cases) [5]

• General symptoms
  • Severe shoulder pain
  • Resistance to shoulder and arm movement
  • Empty glenoid fossa: A palpable or visible dent may be present where the humeral head is expected.
• Anterior shoulder dislocation [2][3]
  • Arm typically held in abduction and slight external rotation (limited adduction)
  • Humeral head palpable below the coracoid process
  • Loss of shoulder contour: prominent acromion and flattening of the deltoid muscle
• Posterior shoulder dislocation [4]
  • Arm held in adduction and internal rotation (limited external rotation)
  • Prominent coracoid process with anterior soft tissue flattening
  • Humeral head not palpable [6]
• Inferior shoulder dislocation [5]
  • Arm held in fixed abduction at ∼ 125° (limited adduction)
  • Humeral head may be palpable in axilla
  • Elbow typically held in flexion with a pronated forearm
  • Axillary nerve injury may be present.

Posterior shoulder dislocation is frequently overlooked during clinical examination. [7]

Clinical evaluation [3][6]

Signs of neurovascular injury or fracture-dislocation on clinical examination should prompt urgent orthopedic consultation.

• Assess for signs of a fracture (e.g., concomitant humerus fracture).
• Conduct a neurovascular examination to identify: [6]
  • Axillary nerve palsy
  • Brachial plexus injury
  • Radial nerve palsy
  • Median nerve palsy
  • Ulnar nerve palsy
• Recurrent uncomplicated anterior shoulder dislocation can be diagnosed clinically. [8]

The risk of concomitant fracture is increased in patients with age > 40 years, first-time dislocation, or a severe injury mechanism (e.g., MVC, fall > 1 flight of stairs, or interpersonal violence). [9]

Axillary nerve injury is common with inferior shoulder dislocation. Document signs of axillary nerve palsy prior to manipulation and reduce without delay (see “Treatment”). [5]

Shoulder x‑ray

• Goal: confirm dislocation and exclude fracture
• Views [10][11]
  • Anteroposterior view (AP view) with the shoulder in internal and external rotation
  • Lateral scapular view (Y view): a radiographic angle where the body of the scapula forms the letter "Y" with the coracoid process and the acromion [11]
  • Axillary view: a radiographic angle visualizing the glenohumeral joint axially from the inferior aspect with the arm in abduction [11]
• Findings
  • Displacement of the humeral head from the glenoid fossa [11]
    • Anterior shoulder dislocation: humeral head may be overlapping with and/or inferior to the glenoid on the AP view; anterior displacement visible on the Y view and axillary view
    • Posterior shoulder dislocation: displacement may not be visible on AP view; posterior displacement visible on the Y view and axillary view
    • Inferior shoulder dislocation: humeral head inferior to the glenoid on the AP view and humerus abducted; inferior displacement visible on Y view [6]
  • Radiographic fracture signs may be present if there is a concomitant fracture.
  • Light bulb sign: diagnostic of posterior shoulder dislocation on the AP view [8]
  • Hill-Sachs lesion and/or Bankart lesion may be visible.

Obtain a Y view and/or axillary view in addition to the AP view to reduce the risk of missing or misclassifying shoulder dislocations (especially posterior shoulder dislocation). [10][11]

MRI [10]

• Goal: deeper evaluation of soft tissue injuries related to dislocation event
• Indications
  • Hill-Sachs lesion or Bankart lesion identified on x-ray
  • Normal x-ray despite history consistent with dislocation event
• Modalities: MRI shoulder without IV contrast or MR arthrography

The primary aim of treatment is to reposition the humeral head into the glenoid cavity and restore full range of motion.

Initial management [6]

• Patients with polytrauma: Follow the ABCDE approach.
• Patients with posterior shoulder dislocation: Treat acute seizures or manage electrical injuries, if present.
• All patients: Manage acute pain and consider a broad arm sling to immobilize in a position of comfort while waiting for imaging.
• If indicated, initiate steps for immediate closed reduction, e.g., preparation for procedural sedation.
• Consult orthopedics if reduction by a specialist or surgery is required.

Closed reduction [6]

Indications

• Consider urgent closed reduction for all uncomplicated shoulder dislocations. [12]
• See “Indications for shoulder reduction” for reasons to consult orthopedics before attempting reduction.

Techniques

• Anterior shoulder dislocation
  • Multiple recommended techniques exist with similar success and complication rates. [12][13][14][15]
  • See “Shoulder reduction” for details on, e.g., scapular manipulation, Milch technique, and traction-countertraction.
  • Procedural sedation is often required.
• Posterior shoulder dislocation: typically reduced under general anesthesia [4]
• Inferior shoulder dislocation [5]
  • Consider traction-countertraction OR gentle rotation of the humeral head to convert it to an anterior dislocation, followed by an anterior dislocation reduction technique.
  • Consult orthopedics if the humeral head is entrapped, e.g., by the glenohumeral ligament or joint capsule.

Post-reduction care [3]

• Repeat neurovascular examination and imaging to evaluate reduction success and identify complications (e.g., Hill-Sachs lesion).
• Apply an arm sling or shoulder immobilizer. [3][16][6][17][18]
• Provide analgesia, e.g., acetaminophen, NSAIDs, and/or ice packs.
• Ensure short-term follow-up (e.g., in 5–8 days) for orthopedics assessment and subsequent rehabilitation.
• Counsel patients on the risk of early recurrence and advise avoidance of contact sports until fully healed. [16]

Conduct a thorough neurovascular examination before and after shoulder reduction to identify axillary nerve injury and other neurovascular injuries as early as possible. [6]

Surgical management

Surgical management may be indicated for complicated shoulder dislocation or for prevention and treatment of recurrent shoulder dislocations.

Complicated shoulder dislocation [3]

• Examples
  • Fracture-dislocation (e.g., concomitant proximal humerus fracture, clavicle fracture, or scapula fracture)
  • Open dislocation
  • Unsuccessful closed reduction
  • Neurovascular injury
  • Associated rotator cuff tear (more common in patients > 40 years of age)
• Management
  • Urgent operative intervention (e.g., ORIF) may be required, e.g., for displaced fracture-dislocations and other associated injuries.
  • Most otherwise uncomplicated irreducible shoulder dislocations are treated with closed reduction under general anesthesia. [3]

Recurrent shoulder dislocation [3][16]

• Risk factors
  • Demographic factors: age < 30 years, active lifestyle, male sex [16]
  • Glenohumeral instability, e.g., caused by Bankart lesions, Hill-Sachs lesions, glenoid labrum injury, glenoid rim fracture (bony Bankart lesion)
• Management: Elective operative intervention is often recommended (e.g., arthroscopic surgery, open surgery).

Young, active patients with first-time uncomplicated shoulder dislocations are likely to benefit from surgery and should be referred to orthopedics after successful closed reduction. [3]

• Neurovascular injury: can be a complication of both dislocation and reduction
  • Axillary nerve injury
  • Brachial plexus injury
  • Injury of the axillary artery and/or axillary vein
• Hill-Sachs lesion ; [19]
  • A depression fracture on the posterolateral surface of the humeral head caused by impact with the glenoid rim
  • Highly prevalent in patients with an anterior shoulder dislocation
  • Increases the risk of glenohumeral instability and recurrent shoulder dislocation
• Bankart lesion
• Avulsion fracture of the major and/or minor tubercles
• Shoulder joint instability
• Rotator cuff injury
• Shoulder stiffness due to prolonged immobilization
• Osteoarthritis of the shoulder joint

A sensory deficit over the lateral surface of the shoulder and limited abduction due to deltoid muscle weakness suggest axillary nerve injury. [8]

We list the most important complications. The selection is not exhaustive.

• High rate of recurrence
• After rotator cuff repair, the rate of recurrence is significantly lower.