Summary Cervical facet dislocations and fractures represent a spectrum of traumatic injuries with varying degrees of cervical instability and risk of spinal cord injury Diagnosis can be confirmed with radiographs or CT scan. An MRI should be performed before surgery to identify an associated disc herniation Treatment usually involves closed or open reduction, followed by surgical stabilization Epidemiology Demographics high-energy trauma in the young motor vehicle and motorcycle accidents high-speed deceleration injury contact sports injuries low-energy trauma in the elderly Anatomic location 17% of all injuries are fractures of C7 or dislocation at the C7-T1 junction reinforces the need to obtain radiographic visualization of the cervicothoracic junction Etiology Pathoanatomy represent a spectrum of osteoligamentous pathology that includes facet fractures more frequently involves the superior facet may be unilateral or bilateral decreases the threshold for facet dislocation loss of tethering effect of the interlocked facets unilateral facet dislocation most frequently missed cervical spine injury on plain x-rays leads to ~25% subluxation on x-ray associated with monoradiculopathy that improves with traction inferior facet of the cephalad vertebrae encroaches on the neuroforamina bilateral facet dislocation leads to ~50% subluxation on x-ray often associated with significant spinal cord injury (~80% of cases) mechanism flexion and distraction forces +/- an element of rotation rotational moment associated with unilateral facet dislocation Associated injuries head injuries noncontiguous spinal injuries often occur in the thoracolumbar, cervicothoracic, and occipitocervical junction appendicular injuries Classification Descriptive (subaxial cervical spine injuries) includes compression fracture burst fracture flexion-distraction injury facet dislocation (unilateral or bilateral) facet fracture more commonly used in the clinical setting Allen and Ferguson Classification (subaxial cervical spine injuries) Typically used for research and not in a clinical setting Based solely on static radiographs and mechanisms of injury 1. Flexion-compression 2. Vertical compression 3. Flexion-distraction Stage 1: Facet sprain with slight subluxation, focal kyphosis <10° Stage 2: Unilateral facet dislocation Stage 3: Bilateral facet dislocation with 50% displacement (perched facets) Stage 4: Complete dislocation (100% displacement) 4. Extension-compression 5. Extension-distraction 6. Lateral flexion Presentation History history of trauma involving a flexion-distraction mechanism obtain relevant past history ankylosing spondylitis/DISH previous cervical spine fusion Symptoms pain neck pain in setting of a flexion-distraction mechanism unilateral dislocation numbness and tingling radiating down a single arm C5-6 presents with numbness in thumb C6-7 presents with numbness in index and middle fingers bilateral dislocation subjective weakness of the bilateral upper and lower extremities paresthesias and sensory changes in bilateral lower extremities Physical exam inspection gross spinal alignment angular deformity may suggest a unilateral facet dislocation scalp and head lacerations or contusions suggest a head injury monoradiculopathy seen in patients with unilateral dislocations C5-6 unilateral dislocation presents with a C6 radiculopathy weakness of wrist extension numbness and tingling in the thumb C6-7 unilateral dislocation presents with a C7 radiculopathy weakness of triceps and wrist flexion numbness in index and middle fingers spinal cord injury symptoms seen with bilateral dislocations symptoms worsen with increasing subluxation perform thorough neurologic examination assess motor and sensory status neurologic reflexes document findings via ASIA scoring Imaging Radiographs views AP, lateral, oblique, and open-mouth odontoid findings lateral x-ray shows subluxation of vertebral bodies unilateral facet dislocation leads to ~25% subluxation on x-ray bilateral facet dislocation leads to ~50% subluxation on x-ray loss of disc height might indicate retropulsed disc in canal widening of the interspinous distance hypolordosis, especially at the injury level soft tissue swelling additional views flexion-extension lateral radiographs indications required whenever facet fracture seen due to the possibility of spontaneous reduction and occult instability CT scan indications most cases findings bony anatomy of the injury malalignment or subtle subluxation of facet facet fracture associated fractures of the pedicle or lamina MRI indications acute facet dislocation in patient with altered mental status must be performed emergently followed by open reduction and stabilization failed closed reduction and before open reduction to look for disc herniation any neurologic deterioration seen during closed reduction any patient going to OR for surgical stabilization needs an MRI in advance timing (controversial) timing of MRI depends on severity and progression of neurologic injury MRI should always be performed prior to open reduction or surgical stabilization if a disc herniation is present with compression of the spinal cord, then an anterior cervical discectomy must be performed findings disc herniations need to know if large anterior disc is present prior to surgery extent of posterior ligamentous injury disruption of the supraspinous and interspinous ligaments posterior longitudinal ligament and posterior annulus disruption 40% of cases in unilateral dislocation 80% of cases in bilateral dislocation sprain or disruption of the posterior facet capsules spinal cord compression or myelomalacia spinal cord hematoma poor prognostic sign for motor recovery Differential Cervical lateral mass fracture separation important to identify as cervical lateral mass fracture separations require fusing two levels, while a facet dislocation only requires fusing a single level Treatment Nonoperative external immobilization x6-12 weeks indications stable facet fracture reduced unilateral facet fractures without radiographic instability and involving <40% of the lateral mass or an absolute height <1 cm must first rule out instability with flexion-extension radiographs technique halo vs. hard orthosis depending on degree of instability and age of patient outcomes >30% rate of subluxation or redislocation increased pain associated with late redislocations high incidence of persistent pain and instability Operative single level instrumented stabilization indications unstable facet fracture bilateral facet fracture unilateral fracture involving >40% of the lateral mass or an absolute height >1 cm technique if no anterior disc herniation, can be performed from anterior or posterior approach emergent closed reduction, emergent MRI, then urgent surgical stabilization indications bilateral facet dislocation with deficits in awake and cooperative patient unilateral facet dislocation with deficits in awake and cooperative patient for a unilateral dislocation with no spinal cord injury, urgency is much less than with a bilateral dislocation timing emergent to obtain reduction, especially when you have bilateral dislocation once reduction is obtained and patient is in a collar, then obtain MRI emergently. If MRI shows reduction and no significant compression on spinal cord, then can perform stabilization on urgent (within 24 hours) basis technique closed reduction usually precedes surgical intervention rarely closed reduction followed by immobilization performed medically frail patients facet dislocations associated with high degree of instability and ligamentous injuries technique never perform closed reduction in patient with mental status changes unilateral dislocations are more difficult to reduce but more stable after reduction bilateral dislocations are easier to reduce (PLL torn) but less stable following reduction outcomes 26% of patients fail closed reduction and require open reduction unilateral facet dislocations can be effectively closed reduced in 25% of cases anterior cervical discectomy and fusion (single level) indications large disc herniation present following reduction with compression on the spinal cord or nerve roots if closed reduction fails, may attempt open reduction from anterior approach by distracting across Caspar pins with simultaneous rotation 1-level interbody arthrodesis with anterior plating posterior reduction & instrumented stabilization indications when no anterior disc present bilateral or unilateral facet dislocations that are not reducible from the front or through closed reduction combined anterior decompression and posterior reduction / stabilization indications when disc herniation present that requires decompression in patient that cannot be reduced through closed or open anterior technique emergent MRI then emergent open reduction surgical stabilization indications facet dislocations (unilateral or bilateral) in patients with mental status changes patients who fail closed reduction technique always obtain MRI prior to open reduction and stabilization if disc herniation with presence of spinal cord compression, use an anterior approach to perform discectomy Techniques Halo external immobilization technique halo is suboptimal in lower cervical spine; therefore, hard orthosis may be satisfactory without complications associated with a halo requires close radiographic follow-up risk of redislocation or subluxation morbidly obese patients may not fit or be adequately stabilized in a halo brace Closed reduction requirements adequate anesthesia sedation supervision of respiratory function serial cross-table laterals ability to perform serial neurologic examinations technique application of Gardner-Wells tongs 1 cm above the pinna and in line with the external auditory meatus below the equator of the skull avoids pin migration and slippage gradually increase axial traction with the addition of weights usually in 5-10 lbs. increments can add up to 140 lbs. of weight or 70% body weight average weight required for reduction ~9.4-9.8 lbs. per segment above the injury level a component of cervical flexion can facilitate reduction flexion moment can be created with pulley system or posterior placement of the Gardner-Wells tongs pins once reduced, decrease traction weight to between 10-15 lbs. and apply an extension moment to the cervical spine adjust pulley system place pad underneath thorax perform serial neurologic exams and plain radiographs after each weight addition abort if there is overdistraction of the spinal segment >1.5 times that of the adjacent uninjured disc space can switch to carbon fiber Gardner-Wells tongs if need to obtain MRI in traction traction limit ~80 lbs. abort if neurologic exam worsens and obtain immediate MRI Anterior cervical discectomy and fusion +/- open reduction indications facet dislocations reduced through closed methods with an MRI showing cervical disc herniation and significant compression on the spinal cord unilateral facet dislocations that fail closed reduction with a disc herniation and significant compression on the spinal cord anterior open reduction techniques can be used to reduce a unilateral facet dislocation standard Smith-Robinson approach generous removal of the anterior-inferior aspect of the cephalad vertebra allows disc space visualization unilateral dislocations can be reduced by distracting vertebral bodies with Caspar pins and then rotating the proximal pin towards the side of the dislocation bilateral dislocations can be reduced by placing converging Caspar pins (10-20° angle) and then compressing the ends together to unlock the facets posterior directed force applied to rostral vertebral body with curette alternatively, lamina spreaders applied to the endplates not effective for reducing bilateral facet dislocations pros and cons overdistraction of the disc space PLL and posterior ligaments are often disrupted excessively large graft may be used to obtain a press-fit interbody graft facet joints will be gapped posteriorly places hardware at risk for failure overdistraction also has risk of spinal cord injury Posterior instrumented stabilization +/- open reduction indications when unable to reduce by closed or anterior approach no anterior compression of spinal cord (no disc herniation) technique instrumentation performed with lateral mass screws reduction Penfield 4 inserted between facets and used to lever back into position can remove the superior aspect of the superior facet of the caudad vertebrae to facilitate a difficult reduction lamina spreaders for distraction of the affected level between the affected spinous processes or lamina usually have to fuse two levels due to inadequate lateral mass purchase at the level of dislocation Combined anterior decompression and posterior reduction / stabilization technique anterior approach first, perform discectomy, position plate, only fix plate to superior vertebral body the plate will prevent graft kick-out, but still allows rotation during the posterior reduction this technique eliminates the need for a second anterior procedure Complications Surgical site infections increased risk with posterior surgery tissue trauma from injury increases risk of infection Recurrent dislocation unilateral dislocations treated with immobilization treated with anterior discectomy, reduction, and interbody fusion Respiratory complications ARDS higher risk in the multitraumatized patient pneumonia due to prolonged recumbency possible need for tracheostomy Vertebral artery injury occurs in up to 11% of patients with cervical spine injuries increased risk when injury involves lateral mass and transverse process often go unrecognized and untreated Esophageal injury related to anterior reduction and fixation primary repair with thoracic surgeon upon identification Pin tract infections associated with halo vest immobilization can result in decreased pin purchase can rarely result in meningitis if the inner table of the skull is violated treat with local care and antibiotics Prognosis Neurologic recovery lower probability of motor improvement with increasingly severe neurologic injury increased age associated with decreased neurologic recovery poor motor recovery potential with spinal cord hematoma