Hangman Fracture

A hangman fracture (traumatic spondylolisthesis of the axis) is a bilateral fracture through the pars interarticularis of the second cervical vertebra (C2), with or without displacement of the C2 body relative to C3. Its name comes from judicial hanging, where hyperextension with distraction produced the injury, but most cases today follow road traffic collisions, falls and diving.

It accounts for 4 to 7% of cervical spine fractures and about 20% of axis fractures, and mostly affects men aged 30 to 50 years.

The Effendi classification, modified by Levine and Edwards, describes:

• type I (translation under 3 mm and no angulation, stable)
• type II (translation over 3 mm with angulation, disc disruption at C2 to C3)
• type IIa (little translation but marked angulation, flexion distraction)
• type III (bilateral facet dislocation at C2 to C3 with fractures of the pars, unstable)

Neurological deficit is uncommon (under 10 to 15%) because the canal is wide at C2 and the fragments decompress it, but vertebral artery injury occurs in up to 15 to 20% and associated head and cervical injuries are common. Most fractures heal with immobilisation (union over 90% for type I and II). Complications are nonunion, malunion, C2 to C3 instability, disc herniation, dysphagia, vertebral artery dissection with stroke, and neck pain.

Pathophysiology.

Hyperextension and axial loading fracture the C2 pars (hangman mechanism), and a secondary flexion force rupture the C2 to C3 disc and posterior ligaments (types II and III). In type IIa, a flexion distraction mechanism produces angulation without translation. The proximity of the vertebral artery in the foramen transversarium within the fractured pars explains the risk of vascular injury.

Upper neck pain and tenderness with muscle spasm, often with the patient holding the head, facial or scalp injury (hyperextension impact), occipital neuralgia, and rarely dysphagia or neurological symptoms. Associated injuries (head injury, other cervical fractures including C1 or the odontoid) are frequent.

Examine under spinal precautions: airway and breathing, cranial nerves, motor and sensory function, reflexes, signs of posterior circulation stroke (vertigo, diplopia, ataxia, dysarthria, Horner syndrome), and pharyngeal swelling.

• CT of the cervical spine with sagittal and coronal reformats: fracture lines through the pars (often asymmetrical, or involving the posterior body or foramen transversarium).
• CT findings also include translation at C2 to C3, angulation (measured as the angle between the inferior endplates of C2 and C3; over 11 degrees is significant), and facet dislocation.
• Lateral radiograph shows the "hangman" lucency at the pars and a retrolisthesis or anterolisthesis of C2 on C3; flexion and extension films should not be done acutely in type II or III.
• CT angiography of the neck for vertebral artery injury in all cases with transverse foramen involvement or neurological signs.
• MRI of the cervical spine for disc disruption at C2 to C3, ligament injury, cord injury and epidural haematoma, particularly before reduction or surgery.

Differential diagnosis.

• Odontoid fracture and Jefferson fracture (C1 burst).
• Congenital spondylolysis of C2 and C2 to C3 congenital fusion.
• Pseudosubluxation in children (physiological anterior displacement of C2 on C3).
• Facet fracture or dislocation at C2 to C3 without pars fracture.

Treatment is determined by the type. Distraction forces must be avoided in types II and IIa.

Type I (stable; translation under 3 mm, angulation under 11 degrees). Rigid collar (cervicothoracic orthosis) for 6 to 12 weeks, with radiographs at 2, 6 and 12 weeks to check alignment; union in over 95%.

Type II.

• Reduction in extension with mild axial compression, then halo vest immobilisation for 8 to 12 weeks (union about 90%); avoid traction (it increases displacement). Early halo immobilisation is poorly tolerated in older patients.
• Surgery for failure to maintain alignment, translation over 5 mm, or marked disc disruption: anterior C2 to C3 discectomy and fusion with plate (preserves rotation) or posterior C2 to C3 fusion, or direct C2 pars screw fixation.

Type IIa. Halo vest with extension and slight compression (not traction); surgery if alignment is lost.

Type III. Surgical stabilisation: reduction of the facet dislocation (open posterior or anterior approach), then C2 to C3 fusion (posterior C2 pedicle or pars screws with C3 lateral mass screws, or anterior plate); union over 95%.

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; with severe penicillin allergy, vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose.

Perioperative adjuncts. Awake fibre optic intubation with minimal neck movement; dexamethasone 8 mg intravenously once at induction for airway swelling in anterior surgery (monitor glucose in diabetes).

Analgesia.

• Paracetamol 1 g orally every 6 hours (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).
• Oral morphine 5 to 10 mg every 4 hours as needed for severe pain for up to 3 to 5 days (start 2.5 to 5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2); monitor sedation and respiration; laxative.
• Neuropathic or occipital pain: gabapentin 300 mg orally at night, increased to 300 to 600 mg three times daily (maximum 3600 mg daily; reduce at creatinine clearance under 60 mL/min).
• Avoid NSAIDs while fusion is awaited.

Vertebral artery injury. If CT angiography shows dissection or occlusion: aspirin 75 to 300 mg orally once daily or enoxaparin 1 mg/kg subcutaneously every 12 hours for 3 to 6 months, balanced against bleeding from associated injuries and surgery; avoid anticoagulation with intracranial haemorrhage or major bleeding. Neurology advice on duration.

Thromboprophylaxis. Enoxaparin 40 mg subcutaneously once daily while immobile (20 mg at creatinine clearance under 30 mL/min), started once bleeding is controlled; mechanical prophylaxis until then.

Halo vest care. Pin site cleaning daily with saline and dry dressing; check pin tightness (torque 0.9 Nm) at 48 hours and weekly; skin under the vest; respiratory physiotherapy.

Flucloxacillin 500 mg to 1 g orally every 6 hours for 5 to 7 days for pin site infection (clarithromycin 500 mg every 12 hours in penicillin allergy, with QT check).

Monitoring. Neurological and airway checks in the first 24 to 48 hours; radiographs or CT at 2 weeks, 6 weeks, 3 months and 6 months to confirm alignment and union; flexion and extension films after immobilisation ends; assessment for stroke symptoms; dysphagia and nutrition.

Referral and escalation. Every suspected hangman fracture needs spinal precautions and transfer to a specialist spinal service. Emergency referral for neurological deficit, stroke symptoms, type III injuries, or loss of alignment.

Special groups.

• Older adults: collar for stable fractures; avoid halo; assess for osteoporosis and falls.
• Pregnancy: collar for stable fractures; limit radiation; MRI without gadolinium.
• Children: pseudosubluxation can mimic the injury; treat true fractures with collar or halo for 6 to 12 weeks.
• Rheumatoid arthritis or ankylosing spondylitis: regard as unstable; surgical stabilisation.