Shoulder Fracture-Dislocations

Fracture-dislocations of the shoulder are a severe subset of proximal humeral injuries. The combination of instability and fracture significantly complicates management, and the priority is a stable reduction that preserves the blood supply to the humeral head.

Who. The pattern is bimodal: high-energy injury in the young, low-energy osteoporotic injury in the elderly. Anterior fracture-dislocations are common in trauma. Posterior dislocations are rare, 2-4% of shoulder dislocations, yet 50% are missed at first presentation.

Mechanism. The direction of the force sets the pattern.

• Anterior: an abduction and external-rotation force. The greater tuberosity shears off, allowing the head to escape anteriorly.
• Posterior: an adduction and internal-rotation force, as in a seizure or electric shock. The head impacts on the posterior glenoid, causing an anterior impression fracture, the reverse Hill-Sachs lesion.

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The greater tuberosity. In an anterior fracture-dislocation the greater tuberosity is often fractured or avulsed. Reducing the head often reduces the tuberosity with it, through the periosteal sleeve and the rotator cuff, but a fragment that remains posterior can block reduction.

• A widely displaced tuberosity compromises cuff function
• A tuberosity that heals in malposition causes impingement and loss of abduction

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The reverse Hill-Sachs lesion. In a posterior fracture-dislocation the head strikes the posterior glenoid rim, leaving an impression fracture of the anteromedial head. If the defect engages the glenoid rim in functional internal rotation, the shoulder will re-dislocate, and it needs structural filling, by transfer or graft, to restore stability.

Defect size. The size of the defect dictates treatment. Under 20% is generally stable and over 40% generally unstable, and a large defect over 40% will re-dislocate if it is not addressed by transfer or arthroplasty.

The blood supply. The arcuate artery, the ascending branch of the anterior humeral circumflex, enters at the bicipital groove and is disrupted in anatomical-neck fractures. Fracture-dislocations have higher rates of AVN, due to extensive soft-tissue stripping and potential tethering of vessels, so gentle reduction is the key to preserving the head.

Predicting ischaemia. Hertel (2004) identified the features that predict an ischaemic head:

• Calcar (metaphyseal extension): less than 8mm attached to the head
• Medial hinge: disrupted, with translation of the head over 2mm
• Fracture pattern: an anatomical-neck fracture

When all are favourable (calcar over 8mm, hinge intact), the risk of ischaemia is low even in complex fractures. When all are unfavourable, they predict ischaemia with a positive predictive value of up to 97%.

Ischaemia is not necrosis. An ischaemic head does not always go on to AVN and collapse; many revascularise by creeping substitution. Hertel judged perfusion at the time of surgery and did not follow patients to collapse, which is how his finding below sits beside the higher AVN rates of fracture-dislocations.

Anterior fracture-dislocation. Counted by the parts involved, and often described as valgus-impacted or displaced.

• 2-part: head dislocated with a greater-tuberosity fracture; head and shaft intact
• 3-part: head dislocated with greater-tuberosity and surgical-neck fractures
• 4-part: head dislocated with greater-tuberosity, lesser-tuberosity and surgical-neck fractures; the tuberosities are separated and AVN risk is high

Posterior locked dislocation.

• Type I: locked posterior dislocation with an impression fracture only
• Type II: posterior dislocation with a surgical-neck fracture, leaving the head free-floating
• Type III: posterior dislocation with a tuberosity fracture

Type II is the dangerous one. Manipulation moves the shaft while the head stays locked, so assess the continuity of the surgical neck carefully before any attempt at reduction.

History. Hold a high index of suspicion for posterior dislocation when the story includes one of these:

• Seizure: an unwitnessed fall, tongue biting, urinary incontinence
• Electric shock: an industrial accident
• Electroconvulsive therapy
• Alcohol intoxication: a fall while unconscious

The anterior shoulder. The arm is held in slight abduction and external rotation. The acromion is prominent, squaring off the shoulder, and the head is palpable anteriorly.

The posterior shoulder. The arm is locked in adduction and internal rotation, and the patient cannot externally rotate, which is pathognomonic. The head makes the back of the shoulder full, and the front is flattened with the coracoid prominent.

Neurovascular status. Checking the axillary nerve and radial pulse is mandatory, and the rate of axillary nerve injury is high. Document the axillary nerve (deltoid contraction and regimental-badge sensation) before and after reduction.

Radiographs. Never accept an AP alone. The trauma series:

• AP: the lightbulb sign of a posterior dislocation, and the overlap sign
• Scapular Y: head position relative to the centre of the Y
• Axillary: the gold standard, defining the direction of dislocation and the state of the tuberosities
• Velpeau view: when the patient cannot abduct for an axillary view

Reading the AP. The central trap of this topic is the posterior dislocation missed on a single AP film. The head can look symmetrical and the overlap misleads, so these signs should make you demand an orthogonal view:

These signs only raise suspicion. An axillary or Velpeau view and CT confirm the diagnosis, and the sizing and engagement of the reverse Hill-Sachs defect are developed in the reverse-hill-sachs-lesions topic.

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CT. Essential for the surgical decision between fixing and replacing. It is indicated to:

• confirm the diagnosis when the radiographs are equivocal or pain limits the views
• quantify the bone defect, the reverse Hill-Sachs percentage
• plan surgery, counting the fragments

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MRI. Not first-line for bone trauma. It assesses the rotator cuff, in the acute anterior dislocation of the elderly, and brachial plexus injury, and is reserved for the soft tissues once the bony options are clear.

Reducing an anterior fracture-dislocation. Use conscious sedation or general anaesthesia and gentle traction-countertraction. Avoid the Kocher leverage manoeuvre, which risks a spiral fracture.

After anterior reduction. Check stability, then treat the greater tuberosity by where it lies:

• Reduces to under 5mm of displacement: conservative, in a sling
• Displaced over 5mm: ORIF with screws or sutures
• Unstable shoulder: surgical stabilisation

Always repeat the radiographs, and often a CT, after reduction to confirm that the reduction is concentric and the tuberosity is in position.

Reducing a posterior fracture-dislocation. Muscle relaxation under general anaesthesia is essential. Apply axial traction with gentle anterior pressure on the head, and do not externally rotate forcefully, because the head is locked.

After posterior reduction. A stable shoulder is immobilised in external rotation in a gunslinger brace for 4 weeks; if it is stable in external rotation, a simple brace may suffice provided the patient is compliant. A shoulder that is unstable because the defect engages needs surgery: a modified McLaughlin or a graft.

The locked posterior dislocation. Defect size and time from injury decide the treatment, as set out in the table below. A medium defect can be filled with a graft as an alternative to the lesser-tuberosity transfer.

Where the cut-offs come from. They vary: 20% and 40% for stability, 20-45% for the transfer and over 45% for arthroplasty, 25% for the defect that must not be ignored. They are conventions from small series, often quoted as 20-25% and 40-50% (see Controversies), and engagement in functional rotation, bone quality and chronicity matter as much as the percentage.

Modified McLaughlin. For a posterior dislocation with a medium defect (20-45%), through a deltopectoral approach. The lesser tuberosity, with subscapularis attached, is moved into the defect. This converts a bone-loss problem into a tendon-transfer solution and prevents the posterior rim from engaging the defect.

1. Identify the lesser tuberosity, which is often intact
2. Osteotomise it with the subscapularis tendon attached
3. Reduce the humeral head, disimpacting it from the glenoid
4. Internally rotate slightly to expose the defect
5. Transfer the lesser tuberosity into the anteromedial defect
6. Fix with two cannulated screws or suture anchors

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ORIF of the anterior fracture-dislocation. For the displaced three- or four-part anterior fracture-dislocation in the young. Reduce the head onto the glenoid first, then fix with a proximal humeral locking plate, pulling the tuberosities to the plate with heavy cuff sutures ("rotator cuff reduction"). Restore medial support with a calcar screw and avoid varus collapse.

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Arthroplasty. Indicated for a head split, a chronic locked posterior dislocation (over 3 weeks) and the elderly patient with poor bone. Hemiarthroplasty is for the young patient with a non-reconstructable head, which is rare. Reverse total shoulder arthroplasty (RTSA) is for the elderly (70+), depends on the deltoid, and is becoming the default for complex fracture-dislocations in the elderly.

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The missed diagnosis. The chronic locked posterior dislocation is common, with an average delay to diagnosis of 3-6 months; in Hawkins' series the mean was a year. It then needs major reconstruction, allograft or arthroplasty, where an early diagnosis needed only a simple reduction.

AVN. Four-part fracture-dislocations have a high AVN rate and can collapse late. Warn the patient before surgery that later conversion to arthroplasty may be needed.

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Recurrent instability. The result of failing to address the defect: a reverse Hill-Sachs lesion over 25% that is ignored will dislocate again.

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Axillary nerve injury. Traction neuropraxia is common, and 90% recover spontaneously in 3-6 months. If deltoid firing has not recovered, request EMG and nerve conduction studies at 6 weeks.

Stiffness and infection. Surgery and immobilisation both cause fibrosis and stiffness, so early range of motion is the key once the shoulder is stable. Secondary adhesive capsulitis is common, and hydrodilatation may be needed later. Infection is a surgical risk.

Heterotopic ossification. Associated with head injury or prolonged coma. Prophylaxis with indomethacin or radiation may be considered in high-risk groups.

What it is. After an anterior glenohumeral dislocation, a rotator cuff tear combined with a neurological injury. The cuff tear is often massive: a first dislocation over 40 carries roughly a 30% cuff-tear risk, and over 60 more than 80%. The nerve is most often the axillary, sometimes a wider infraclavicular brachial-plexus lesion.

Why it is missed. After reduction the cuff tear and the nerve injury mask each other, and the dislocation masks both. Persistent inability to abduct or elevate is wrongly blamed on pain and stiffness, or on an axillary nerve palsy, when a large, repairable cuff tear is being missed, or the reverse.

Sorting it out. The pre- and post-reduction axillary nerve examination is the baseline.

• If the deltoid is firing but the patient still cannot actively elevate at 2 to 3 weeks, suspect a rotator cuff tear and image with ultrasound or MRI
• If a neurological deficit persists, EMG/NCS at about 3 to 6 weeks characterises the lesion

Management. The components run on their own tracks. An acute, repairable cuff tear in an active patient is repaired, often once the nerve picture has clarified, while the nerve injury is usually observed; an older patient with an irreparable massive cuff tear and an axillary injury may ultimately need reverse arthroplasty. Detailed cuff and axillary nerve management belong to their own topics; the examiner's point is to recognise the triad and not stop at the first diagnosis.

By injury. A simple dislocation with a greater-tuberosity fracture has an excellent outcome if the tuberosity heals anatomically. The missed posterior dislocation does poorly without surgery; arthroplasty is usually successful for pain, but range of motion is limited.

By operation. The McLaughlin procedure gives good outcomes for medium defects with a low recurrence rate. RTSA gives predictable elevation to 130 degrees and good pain relief, though functional rotation is often limited.

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Global epidemiology

• Posterior fracture-dislocation incidence is approximately 0.6 per 100,000 per year, with a peak in middle-aged men (Robinson 2007).
• Posterior dislocations make up only 2-4% of shoulder dislocations but are missed initially in up to half of cases.
• Bimodal injury pattern: high-energy trauma in the young versus low-energy osteoporotic injury in the elderly.

Society guidance, side by side

Registry signals

• Arthroplasty registries (AOANJRR, NJR, AJRR, Swedish/Norwegian) show a sustained shift from hemiarthroplasty toward reverse total shoulder arthroplasty for acute fracture in older patients, mirroring RCT evidence (Sebastia-Forcada 2014).
• RCT-level evidence (PROFHER) shows no benefit of surgery over nonoperative care for isolated displaced surgical-neck fractures, so registry surgery trends should be read as selective, not blanket.

High- versus limited-resource practice

• High-resource: routine CT for defect quantification, axillary/Velpeau views, arthroplasty backup, sub-specialist upper-limb referral for chronic locked dislocations.
• Limited-resource: reliance on plain orthogonal radiographs, greater use of closed reduction and transfer procedures, and earlier acceptance of deformity when implants are unavailable.

Related pages: Proximal Humerus Fractures is the parent injury and carries the Neer classification, the fixation techniques and the PROFHER debate in full - remember PROFHER studied surgical-neck fractures and excluded the fracture-dislocation this page covers; Posterior Shoulder Instability and Reverse Hill-Sachs Lesions for the posterior injury spectrum and the impression-defect ladder that decides between transfer, graft and arthroplasty; Anterior Shoulder Instability and Hill-Sachs Lesions for the anterior mirror; Greater Tuberosity Fractures for the fragment whose displacement after reduction most often changes the plan; Avascular Necrosis of the Shoulder for what happens when the Hertel criteria are unfavourable and the head is fixed anyway; Reverse Total Shoulder Arthroplasty for the salvage carded above; and Axillary Nerve Anatomy for the nerve to document before and after any reduction attempt.

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