A significant minority of shoulder dislocations involve an associated injury, such as fracture, tendon or ligament tear, or neurovascular injury.
Fractures occur in about 30% of cases. The most commonly seen fractures are:
Hill-Sach’s Lesion (hatchet deformity)
Seen in 54-76% of cases, this is a compression fracture that results in the formation of a groove in the posterolateral aspect of the humeral head. It is best viewed on x-ray with internal rotation of the arm and should be looked for in all post-reduction x-rays.
Classically this is described as separation of the joint capsule and/or labrum from the anteroinferior glenoid rim, however the term is commonly used to refer to bony disruption of the glenoid (aka bony Bankart’s lesion).
It is the result of impaction of the humeral head against the anteroinferior glenoid labrum during dislocation, and is associated with rupture of joint capsule and inferior glenohumeral ligament damage.
It is more common in younger patients and has a strong association with recurrent dislocations (85-87%)
MRI is the imaging of choice for this lesion.
Other less common bony-type injuries include
- SLAP lesions (Superior Labral tear, Anterior to Posterior)
- Avulsion fracture of the greater tuberosity (10-16% of cases)
- Coracoid fracture which can be damaged by the humeral head during dislocation and may result in painful non-union.
- Humeral shaft fracture – this rare complication is associated with significant forces around the shoulder joint and humeral shaft and should be looked for in any high impact trauma where dislocation is suspected.
The glenohumeral ligaments are important static stabilisers, and are damaged in about 55% of cases, especially in young patients. Injury to the anterior band of the inferior glenohumeral ligament (as part of the classical Bankart’s lesion) is associated with instability and recurrence.
Rotator cuff injury
The rotator cuff is more commonly damaged in older patients. Consider ultrasound follow-up for older patients, especially if weakness and poor joint function persists for more than four weeks.
Some form of neurological damage occurs in 21-50% of cases. The axillary nerve is the most commonly damaged, however brachial plexus and other isolated nerve injuries can occur.
Brachial plexus injuries have an association with axillary artery damage. Initial neurological assessment post reduction can be limited by pain and sedation, so if a nerve injury is noted pre- or post- reduction then a follow up examination is essential.
Axillary artery rupture presents with pain, axillary haematoma and a cool limb with absent pulses. However, the presence of distal pulses may still occur, resulting from collateral flow. Although this complication is very rare, consider this if a brachial plexus injury is identified, especially in patients aged >50.