Anterior Shoulder Dislocation

Anterior shoulder dislocation is displacement of the humeral head in front of the glenoid. It accounts for about 95 to 97% of shoulder dislocations and is the most common major joint dislocation, with an incidence of about 20 to 25 for every 100 000 people each year. The peaks are young men aged 15 to 30 years after sport or falls, and older adults after low energy falls.

The head usually lies in the subcoracoid position, less often subglenoid, subclavicular or intrathoracic. It follows an abduction and external rotation force or a fall on the outstretched arm.

Associated injuries:

• Bankart lesion (anteroinferior labral avulsion, in over 90% of first time dislocations in young people).
• Hill-Sachs lesion (posterolateral humeral head impaction, in up to 80%).
• Bony Bankart (glenoid rim fracture).
• Greater tuberosity fracture (about 15%).
• Rotator cuff tear (30% over age 40 and up to 80% over age 60).
• Axillary nerve injury (up to 30%, often transient).
• Axillary artery injury (rare, more frequent in older adults).

Complications are recurrent instability (up to 70 to 90% under age 20 with non-operative care, under 20% over age 40), stiffness, arthritis, nerve injury and rotator cuff failure.

Pathophysiology.

Forced abduction, extension and external rotation levers the head over the anteroinferior glenoid rim and tears the anterior capsule and labrum from the glenoid. The head rests on the glenoid edge and creates a posterolateral impaction fracture.

Each recurrence adds bone loss from the glenoid and humeral head, which raises the risk of further dislocation. Glenoid bone loss of over 20 to 25% (an inverted pear glenoid) or an engaging Hill-Sachs lesion predicts failure of soft tissue repair.

Severe pain, with the arm held slightly abducted and externally rotated, supported by the other hand. The shoulder loses its round contour (squared off) with a prominent acromion and a palpable head in front. Movement is blocked, particularly internal rotation.

Examine the neurovascular state before and after reduction: axillary nerve (sensation over the lateral deltoid, "regimental badge" area, and deltoid contraction), musculocutaneous, radial, median and ulnar nerves, the radial pulse and capillary refill. Look for associated injuries (neck, chest, elbow).

• Radiographs: anteroposterior, scapular Y and axillary views before reduction (to exclude fracture and to confirm direction) and after reduction (to confirm the position and show the Hill-Sachs lesion). The West Point or Bernageau view shows the glenoid rim.
• CT for glenoid bone loss, large Hill-Sachs lesions, fractures and recurrent dislocation.
• MRI or MR arthrogram for the labrum, rotator cuff and capsule, particularly over age 40.
• Ultrasound for rotator cuff tears in older adults.
• Nerve conduction studies and electromyography at 3 to 4 weeks for a persisting deficit.

Differential diagnosis.

• Posterior shoulder dislocation and proximal humerus fracture.
• Acromioclavicular joint separation and sternoclavicular dislocation.
• Rotator cuff tear and brachial plexus injury.
• Luxatio erecta (inferior dislocation).

Closed reduction as soon as possible, after radiographs, with analgesia and relaxation.

• External rotation method (low force): with the elbow flexed to 90 degrees and held against the side, gently rotate the arm outwards over 2 to 3 minutes until a clunk.
• Scapular manipulation: with the patient prone or sitting, apply gentle traction to the arm and rotate the tip of the scapula medially while pushing the inferior tip toward the spine.
• Other methods also work:
  • Traction countertraction (a sheet around the axilla).
  • Cunningham massage technique.
  • Milch technique (abduct and externally rotate to overhead, then apply thumb pressure to the head).
  • Stimson method (prone with hanging weights of 2.5 to 5 kg for 15 to 20 minutes).
• The Kocher manoeuvre is not used because it risks fracture and nerve injury.
• Multiple failed attempts: reduce under general anaesthesia. Irreducible dislocation (interposed biceps tendon, capsule, a displaced fracture): open reduction.

Intra-articular anaesthesia. Lidocaine 1% (10 mg/mL) 10 to 20 mL injected into the joint from the lateral approach with aseptic technique as a single administration (maximum 4.5 mg/kg of plain lidocaine and not exceeding 300 mg). Wait 10 to 15 minutes. Monitor for toxicity (perioral numbness, tinnitus, drowsiness). Avoid with infection at the site or lidocaine allergy.

Reduction under sedation. Ketamine 1 to 2 mg/kg intravenously over 1 to 2 minutes as a single dose (a further 0.5 to 1 mg/kg after 10 minutes if needed; 4 to 5 mg/kg intramuscularly without access). It is given by a clinician skilled in airway care with continuous oximetry and capnography, after fasting where time allows. Avoid with raised intracranial pressure, psychosis or acute upper airway infection.

After reduction.

• Check the neurovascular state again and take post-reduction radiographs.
• Sling for comfort for 1 to 3 weeks (a short period, with early pendulum and range-of-motion exercises). Prolonged immobilisation does not reduce recurrence.
• Physiotherapy: rotator cuff and scapular stabiliser strengthening over 6 to 12 weeks. Avoid contact sport for 3 to 6 months.
• Surgical stabilisation:
  • After a first dislocation for young athletes or contact sports players (arthroscopic Bankart repair with suture anchors, recurrence 5 to 15%).
  • For glenoid bone loss over 15 to 25% (Latarjet coracoid transfer or bone graft).
  • For engaging Hill-Sachs lesions (remplissage).
  • Over age 40, repair the rotator cuff tear early if present.
• Axillary nerve palsy: observe, with electromyography at 3 to 4 weeks; explore if there is no recovery by 3 to 6 months.

Operative antibiotic prophylaxis. Cefazolin 2 g intravenously (3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose (repeat after 4 hours or blood loss over 1500 mL). With severe penicillin allergy, vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose, with levels and creatinine checked in prolonged cases.

For shoulder surgery add benzoyl peroxide 5% topically to the skin the day before and morning of surgery when local practice supports it.

Analgesia.

• Paracetamol 1 g orally every 6 hours as needed for up to 5 to 7 days (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).
• Ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily); avoid with eGFR under 30 mL/min/1.73 m2, peptic ulcer, heart failure or anticoagulant use.
• Oral morphine 5 to 10 mg every 4 hours as needed for severe pain for up to 3 days (start 2.5 to 5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2; avoid exceeding 60 mg in 24 hours without senior review). Monitor sedation and respiration and prescribe a laxative.

Monitoring. Neurovascular state before and after reduction and at 2 weeks. Range of motion and rotator cuff strength at 2 weeks, 6 weeks and 3 months. Repeat radiographs at 1 to 2 weeks if there is a fracture. Recurrent instability at each visit, with MRI or CT if it recurs. Electromyography at 3 to 4 weeks for a persisting nerve deficit.

Referral and escalation. Refer first time dislocation in an athlete or young patient to orthopaedics or sports surgery within 2 weeks for a surgical opinion. Refer over age 40 with weakness, an irreducible dislocation, associated fracture dislocation, or recurrent instability. Emergency referral for vascular compromise, open dislocation, or a progressive nerve deficit.

Special groups.

• Children and adolescents: physeal injuries are more common than dislocation; recurrence is very high in adolescents, so early surgical stabilisation is considered.
• Older adults: reduce gently with relaxation, because of the risk of fracture, rotator cuff tear and axillary artery injury; avoid prolonged immobilisation.
• Seizure disorders and alcohol: posterior and bilateral dislocations occur; examine carefully.
• Kidney impairment: avoid ibuprofen and reduce morphine doses.