Anterior Dislocation of the Shoulder — Diagnosis, Reduction & Recurrence

The anterior dislocation is the commonest large-joint dislocation. The arm is held abducted and externally rotated with loss of the deltoid contour (squaring); the axillary nerve must be tested before and after reduction. Reduction (Kocher, Hippocratic, Stimson or Milch) is followed by a sling. Recurrence is driven by the Bankart lesion (labral avulsion) and the Hill–Sachs lesion (humeral head impaction).

Introduction

The shoulder is the most commonly dislocated large joint in the body because its stability is sacrificed for mobility — a large humeral head articulates with a small, shallow glenoid. Over 95% of dislocations are anterior, and of these the sub-coracoid position is the commonest. The mechanism is a fall on the outstretched hand with the arm in abduction and external rotation, or a direct blow to the back of the shoulder.

Clinical Features

The patient supports the injured arm and holds it slightly abducted and externally rotated, resisting any movement. The normal rounded contour of the shoulder is lost — the deltoid appears flattened and the acromion becomes prominent, giving the characteristic 'squaring' of the shoulder. There is an anterior fullness where the humeral head can be palpated below the coracoid. Dugas' test is positive — the patient cannot place the hand of the affected side on the opposite shoulder. Before and after reduction, the axillary nerve must be tested by checking sensation over the 'regimental badge' area on the lateral aspect of the upper arm (and, once pain allows, deltoid contraction), as it is the nerve most commonly injured.

Radiology

An AP view plus a second view at right angles (an axillary or a scapular 'Y' view) is essential — a single AP can miss a posterior dislocation, which is the classic exam trap (seen after epileptic seizures or electric shock, giving the 'light-bulb' sign of the internally rotated head). Radiographs also confirm reduction and exclude an associated fracture.

Management — Reduction

The dislocation is reduced as an emergency, under sedation or general anaesthesia and with muscle relaxation. Several techniques exist: KOCHER'S method (traction in the line of the arm, then external rotation, adduction across the chest, and finally internal rotation — effective but with a risk of humeral fracture if done forcibly), the hippocratic method (traction and counter-traction), the stimson technique (the patient lies prone with a weight hanging from the wrist, allowing gentle spontaneous reduction), and the MILCH manoeuvre. After reduction the neurovascular status is rechecked, a confirmatory X-ray is taken, and the arm is rested in a sling for about three weeks, followed by graded rotator-cuff and deltoid rehabilitation.

Recurrent Dislocation

Recurrence is common, especially in young, active patients (the younger the patient at first dislocation, the higher the risk). It is driven by two lesions produced at the first dislocation: the bankart lesion — an avulsion of the antero-inferior glenoid labrum with its capsule (the 'essential lesion' of recurrent anterior instability) — and the hill–SACHS lesion — a compression (impaction) fracture of the postero-lateral humeral head where it strikes the glenoid rim. The apprehension test (the patient becomes apprehensive when the shoulder is abducted and externally rotated) is diagnostic of instability. Established recurrent instability is treated surgically — a Bankart repair (arthroscopic or open reattachment of the labrum), or a bone procedure (Latarjet) where there is significant glenoid bone loss.

• The shoulder is the commonest large joint to dislocate; >95% are anterior (sub-coracoid commonest), from a FOOSH in abduction–external rotation.
• Signs: arm held abducted/externally rotated, loss of deltoid contour (squaring), anterior fullness, Dugas' test positive. Always test the axillary nerve (regimental badge) before and after reduction.
• Get an AP plus a second view (axillary or scapular-Y) — a single AP misses posterior dislocation (seizure/shock; light-bulb sign).
• Reduce under sedation/anaesthesia: Kocher's, Hippocratic, Stimson or Milch; then sling ~3 weeks + confirmatory X-ray. Look for greater-tuberosity fracture in the elderly.
• Recurrence (high in the young) is driven by the bankart lesion (antero-inferior labral avulsion — the essential lesion) and the hill–SACHS lesion (humeral-head impaction); apprehension test positive → Bankart/Latarjet repair.