Subaxial Cervical Spine Fractures

Subaxial injuries, those from C3 to C7, account for approximately 50% of all cervical spine fractures. They carry significant morbidity because of the high rate of associated spinal cord injury, present in up to 55%.

Who. The age distribution is bimodal: young patients injured in trauma, and elderly patients who fall. Males outnumber females 3:1, and motor vehicle accidents and falls are the primary mechanisms.

Where. C5-C6 is the most commonly injured level. It is the segment of greatest mobility, and it sits at the transition zone between the more mobile middle cervical spine and the relatively stiffer lower cervical spine; that biomechanical transition creates a stress concentration point.

Mechanism. The loading pattern determines the injury it produces:

• Flexion-compression - burst fractures, teardrop fractures
• Extension-compression - lamina fractures, hangman's variants
• Flexion-distraction - facet dislocations, posterior ligament disruption
• Axial compression - burst fractures
• Lateral flexion - unilateral injuries

The motion segment. The subaxial spine has consistent anatomy from C3 to C7, and each structure has its own job:

• Vertebral body - the primary load-bearing structure
• Facet joints - a 45-degree orientation that guides motion
• Uncovertebral joints - resist lateral translation
• Intervertebral disc - shock absorption and motion
• Ligamentous structures - stability through the range of motion

The levels differ in motion and clinical significance:

The disco-ligamentous complex. The DLC is the primary determinant of stability. It comprises:

• Intervertebral disc
• Anterior longitudinal ligament (ALL)
• Posterior longitudinal ligament (PLL)
• Ligamentum flavum
• Interspinous and supraspinous ligaments
• Facet capsules

The cord. The cervical cord enlargement runs from C4 to T1, so injury at these levels carries a higher consequence. The space available for the cord is the canal diameter minus the cord diameter: a normal canal is approximately 17mm and the cord approximately 10mm. Stenosis increases the severity of injury for the same energy.

The roots. Cervical nerve roots exit above their numbered vertebra, so the C6 root exits the C5-C6 foramen. C8 is the exception and exits below C7, since there is no C8 vertebra. Root injury is more common than cord injury in unilateral facet injuries, and cord injury is more common with bilateral facet dislocations.

History. The questions to ask:

• Mechanism of injury (high vs low energy)
• Time since injury
• Any neurological symptoms (weakness, numbness, bladder/bowel)
• Previous cervical spine problems
• Medical comorbidities affecting the surgical decision

The primary survey. Consider early intubation if unstable, and expect diaphragmatic breathing with a high cord injury. Bradycardia with hypotension is neurogenic shock. Look for associated head, chest and polytrauma injuries.

The spine. Inspect for bruising, deformity and a step-off, and palpate for tenderness and interspinous widening. Do NOT test range of motion if instability is suspected, and log-roll to clear the entire spine.

Neurology. Grade the cord injury on the ASIA Impairment Scale.

The level of a deficit is read from the sensory landmarks and key muscles:

Differential diagnosis. The key reasoning step is separating a genuinely unstable subaxial fracture (operative threshold) from mimics that change urgency or treatment.

Algorithm

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The decision. Once the patient is safe, the SLIC score sets the threshold and the patterns fall into four bands:

Non-Operative ManagementOperative IndicationsApproach Selection

Indications for Non-Operative Treatment

Who. SLIC 0-3 with an intact disco-ligamentous complex, no neurological deficit, minimal displacement and a stable fracture pattern.

The protocol. A hard collar (Miami J or Philadelphia) for 6-12 weeks, with serial lateral X-rays at 2, 6 and 12 weeks to look for progressive kyphosis or translation. Range-of-motion exercises begin once the collar is removed, with physiotherapy for strengthening.

Watching for failure. New neurological symptoms call for an urgent MRI, and failure to heal at 12 weeks means considering surgery.

When Non-Op Fails

Conversion to surgery indicated for:

• Progressive kyphosis more than 10-15 degrees
• Late neurological deterioration
• Persistent instability on flexion-extension films
• Non-union at 3-6 months

Surgical Indications

Absolute indications. Surgery is indicated for:

• SLIC score 5 or more
• Incomplete neurological deficit with ongoing compression
• Unstable fracture-dislocation
• Bilateral facet dislocation
• Progressive neurological deficit

Relative indications. Surgery may be chosen for:

• SLIC 4 (surgeon discretion)
• Polytrauma requiring early mobilisation
• Inability to tolerate a collar (burns, skin breakdown)
• Patient preference with appropriate counselling

Timing. The neurology sets the clock. A complete injury has stable neurology and timing is less critical; for an incomplete injury with compression, urgent decompression within 24 hours improves outcomes on the STASCIS data.

• Urgent (less than 24h): incomplete SCI with ongoing compression
• Early (24-72h): most unstable injuries without SCI
• Delayed: stable patients, complete SCI

Read the delayed tier against the 2024 AO Spine guideline in the Evidence Base, which recommends early surgery (24 hours or less) as the preferred option for adult acute SCI regardless of level.

STASCIS Evidence

The Surgical Timing in Acute Spinal Cord Injury Study (STASCIS) found that decompression within 24 hours for cervical SCI was associated with at least a 2-grade AIS improvement at 6 months in 19.8% versus 8.8% after later surgery - odds ratio 2.57 (95% CI 1.11-5.97), and 2.83 (1.10-7.28) after adjustment for preoperative neurological status and steroid administration. Two qualifications make it quotable rather than merely quoted. It is a prospective COHORT study, not a randomised trial, so surgeons chose the timing and confounding by indication runs in both directions. And it answers the usual objection to operating early: complications were 24.2% in the early group against 30.5% late (p=0.21), with one death in each - early decompression was not the more dangerous option.

Anterior vs Posterior Approach

Anterior. Indicated for a vertebral body fracture requiring corpectomy, a disc herniation causing ventral compression, kyphotic deformity correction and anterior column deficiency. It decompresses ventral pathology directly, corrects kyphosis better, needs a single (supine) position and uses anatomy familiar to most surgeons.

Posterior. Indicated for a facet fracture or dislocation, a lamina fracture or other posterior element injury, posterior tension band disruption and the need for multilevel fixation. Lateral mass screws give stronger fixation, facet reduction is easier, posterior ligament injury can be addressed, and more levels can be instrumented.

Combined. Indicated for severe (three-column) instability, anterior corpectomy with posterior tension band failure, when circumferential decompression is needed, and for revision of a failed single approach.

Compression fracture with retropulsion

Preferred Approach

Anterior corpectomy

Rationale

Direct decompression of canal

Burst fracture with kyphosis

Preferred Approach

Anterior corpectomy + cage

Rationale

Restores height and lordosis

Unilateral facet dislocation

Preferred Approach

Posterior reduction + fusion

Rationale

Facet reduction easier posteriorly

Bilateral facet dislocation

Preferred Approach

Posterior first, consider anterior

Rationale

Reduce facets, then stabilise

Fracture-dislocation with SCI

Preferred Approach

Combined anterior-posterior

Rationale

Maximum stability and decompression

Approach Selection Guide

Injury Pattern	Preferred Approach	Rationale
Compression fracture with retropulsion	Anterior corpectomy	Direct decompression of canal
Burst fracture with kyphosis	Anterior corpectomy + cage	Restores height and lordosis
Unilateral facet dislocation	Posterior reduction + fusion	Facet reduction easier posteriorly
Bilateral facet dislocation	Posterior first, consider anterior	Reduce facets, then stabilise
Fracture-dislocation with SCI	Combined anterior-posterior	Maximum stability and decompression

When MRI shows a disc herniation at the dislocated level, the posterior-first row does not apply: the anterior discectomy comes before any reduction (see the Combined Approach under Surgical Technique).

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Central Cord Syndrome

Central cord syndrome is the commonest incomplete cord syndrome and a quintessentially subaxial problem. It is distinct from the unstable-fracture algorithm above, and it is examined as the "old person who fell and can't use their hands".

Who. Typically an older patient with a spondylotic, stenotic cervical spine who sustains a hyperextension injury, often a fall onto the face or forehead, frequently with no fracture or only minor injury. The cord is pinched between anterior osteophytes or disc and the inbuckling ligamentum flavum posteriorly.

The deficit. The upper limbs are affected more than the lower limbs, the hands worst of all, with variable sensory loss and sometimes bladder dysfunction, because the centrally located cervical (hand) motor fibres are preferentially injured.

Diagnosis. MRI shows central cord oedema or haemorrhage on a background of stenosis, usually without instability on CT, in contrast with the SLIC fracture pathway.

Management. Many patients recover substantially with supportive care (MAP support, and no fracture to fix), so treatment was historically non-operative. The modern trend favours decompression, often subacute or early, for significant ongoing cord compression, especially if recovery plateaus; timing is debated and individualised. Recovery follows a typical pattern: the legs recover before the hands, with hand intrinsic function the last and least to return.

Pre-operative Planning

Consent. Cover neurological worsening, infection (superficial 2-3%, deep less than 1%), dysphagia and recurrent laryngeal nerve injury after anterior surgery, hardware failure, and adjacent segment disease as a long-term risk; the rates are in the Complications table.

Equipment. Check before starting:

• Imaging - fluoroscopy or navigation
• Implants - plates and screws (anterior), lateral mass screws (posterior)
• Cage or graft - structural allograft or cage for corpectomy
• Neuromonitoring - SSEPs and MEPs
• Cell saver - for multilevel procedures

Anterior ApproachPosterior ApproachCombined Approach

Anterior Cervical Approach (Smith-Robinson)

Step-by-Step Technique

Step 1Positioning

Supine on radiolucent table. Head in neutral with gentle traction (Gardner-Wells if needed). Shoulder roll to extend neck. Arms tucked at sides.

Step 2Approach

Transverse incision at appropriate level (C5-6 at thyroid cartilage). Develop plane between carotid sheath laterally and trachea/oesophagus medially. Retract longus colli muscles.

Step 3Exposure

Identify level with fluoroscopy. Mark with needle if uncertain. Expose vertebral bodies and discs. Preserve anterior longitudinal ligament if possible.

Step 4Decompression

Discectomy or corpectomy as indicated. Remove PLL to decompress canal. Visualise dura. Remove retropulsed fragments.

Step 5Reconstruction

Cage or graft to restore height. Size appropriately (1-2mm larger). Position centrally. Confirm alignment on fluoroscopy.

Step 6Fixation

Anterior plate spanning construct. Bicortical screws (4-5mm engaging posterior cortex). Confirm position with lateral fluoroscopy.

Avoid Oesophageal Injury

Oesophageal perforation is rare but devastating. The risk rises with previous anterior surgery, prominent osteophytes, excessive retraction and a long operative time. Protect the oesophagus with gentle retractor placement and intermittent release.

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Posterior Cervical Approach

Step-by-Step Technique

Step 1Positioning

Prone on Jackson table or with Mayfield head holder. Ensure neck neutral to slight flexion. Eyes and pressure points padded. Arms tucked.

Step 2Approach

Midline incision over spinous processes. Dissect subperiosteally to lateral mass. Maintain haemostasis. Identify levels with fluoroscopy.

Step 3Lateral Mass Screws

Entry point: 1mm medial and 1mm caudal to centre of lateral mass. Trajectory: 30 degrees lateral, 15-20 degrees cephalad. Depth 14-18mm.

Step 4Reduction (if facet dislocation)

Open facet joint capsules. Gentle distraction. Use Moe or Penfield to reduce locked facets. Confirm reduction with fluoroscopy.

Step 5Decompression (if needed)

Laminectomy or laminoplasty for posterior compression. Foraminotomy for root decompression. Preserve as much bone as possible.

Step 6Fusion

Decorticate lateral masses and facets. Apply local autograft (from laminectomy) and/or allograft. Compress across construct.

Lateral Mass Screw Safety

The vertebral artery is at risk if screws are placed too laterally or the trajectory is too medial. The step 3 angles are the Magerl technique, and they keep screws safe.

Combined Anterior-Posterior Approach

The indications are set out under Approach Selection. The practical questions are when to operate and in which order.

Staging options

1. Same day anterior-posterior: flip the patient (longer, single anaesthetic)
2. Staged: posterior first, anterior 5-7 days later (allows swelling to settle)
3. Anterior-posterior-anterior: rare, for extreme instability

Sequence. Go posterior first if facet reduction is needed, since it allows reduction before anterior fixation, and anterior first if the primary pathology is ventral and the posterior stage is supplemental. A disc herniation at a dislocated level reverses the facet rule: any reduction manoeuvre, closed or open, can retropulse disc material into an already injured cord, so the anterior discectomy comes first and the posterior reduction and fixation follow.

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Combined Approach Risks

Combined approaches carry a longer operative time, greater blood loss, a higher infection rate and increased swelling with airway compromise. Consider staging if there is significant anterior oedema.

Intraoperative Troubleshooting

Neurological deterioration is the most feared complication, and the risk is higher with incomplete SCI. Beyond the measures in the table, avoid over-distraction.

Dysphagia after anterior surgery usually resolves within weeks but persists in 5-10%. Consider thin liquids initially and a speech pathology review.

Delayed instability. A small fracture does not make a tension-band injury stable, and a disco-ligamentous injury that is underestimated can declare itself later, even in a brace.

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The collar. Most surgeons use a hard collar for 6-12 weeks after surgery. It comes off earlier with rigid internal fixation and good bone quality, and stays on longer for osteoporosis, a multilevel construct or concern about stability.

Neurological recovery. A complete injury (ASIA A) carries minimal expected recovery, and care focuses on rehabilitation. An incomplete injury has significant potential for recovery, especially with early decompression, and a root injury usually recovers well over 6-12 months.

What drives outcome. Outcome depends on the severity of the initial injury, the timing of decompression for incomplete SCI, the quality of reduction and stabilisation, patient factors (age, comorbidities, smoking) and compliance with rehabilitation.

Early surgery. Early surgery (less than 24 hours) for incomplete SCI results in a shorter ICU stay and faster rehabilitation.

The long term. Hardware removal is rarely needed unless symptomatic, surveillance for late instability is ongoing, and return to contact sports is controversial.

Global epidemiology. Subaxial injuries account for approximately half of cervical spine fractures, with C5-C6 the most frequently injured level (the mobile-to-stiff transition zone). Across resource settings the demographic is consistent: predominantly young males injured by road traffic accidents, with falls dominating in the elderly. In a meta-analysis of 11,639 patients across 16 African countries, road traffic accidents caused 49.5% of traumatic spine injuries, the cervical spine was the most common level (51.6%), patients were 81% male with a mean age of 34.5 years, and surgery was performed in only 31.9% versus a majority managed conservatively, with 12.1% mortality (Darko et al, J Neurosurg Spine 2025, DOI). This contrasts with high-income systems where most unstable injuries are operated early.

Registry & systematic-review evidence. Cervical trauma is not captured by arthroplasty joint registries; the comparative evidence base is national trauma databases and pooled reviews rather than a single implant registry. Pooled data in rigid (ankylosing) cervical spines - a high-risk subaxial subgroup - confirm the C6-C7 / C5-C6 predominance and show combined anterior-posterior constructs carry the lowest reoperation rate (1.7%) versus anterior-only fixation (11.1%) (Musa et al, Neurosurg Rev 2025, DOI).