Summary Cervical Facet Dislocations and Fractures represent a spectrum of traumatic injury with a varying degree 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 disk herniation. Treatment usually involves closed or open reduction followed by surgical stabilization. Epidemiology Demographics high energy trauma in young motor vehicle accidents and motor cycle accidents high speed deceleration injury contact sports injuries low energy trauma in elderly Anatomic location 17% of all injuries are fractures of C7 or dislocation at the C7-T1 junction this reinforces the need to obtain radiographic visualization of the cervicothoracic junction Etiology Pathoanatomy represent spectrum of osteoligamentous pathology that includes facet fractures more frequently involves superior facet may be unilateral or bilateral decreases the threshold for facet dislocation loss of tethering effect of interlocked facets unilateral facet dislocation most frequently missed cervical spine injury on plain xrays leads to ~25% subluxation on xray associated with monoradiculopathy that improves with traction inferior facet of the cephalad vertebrae encrouches the neuroforamina bilateral facet dislocation leads to ~50% subluxation on xray 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 occurs in the thoracolumbar, cervicothoracic, and occipitocervical junction appendicular injuries Classification Descriptive classification (subaxial cervical spine injuries) includes compression fracture burst fraction flexion-distraction injury facet dislocation (unilateral or bilateral) facet fracture more commonly used in clinical setting Allen and Ferguson Classification (of 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 flexion-distration mechanism obtain relevant past history ankylosing spondylitis / DISH previous cervical spine fusion Symptoms pain neck pain in setting of 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 finger bilateral dislocation subjective weakness in b/l upper and lower extremeties paresthesias and sensory changes in b/l lower extremities Physical exam inspection gross spinal alignment angular deformity may suggest a unilateral facet dislocation scalp and head lacerations or contusions suggest a overlying head injury monoradiculopathy seen in patients with unilateral dislocations C5/6 unilateral dislocation presents with a C6 radiculopathy weakness to wrist extension numbness and tingling in the thumb C6/7 unilateral dislocation presents with a C7 radiculopathy weakness to triceps and wrist flexion numbness in index and middle finger spinal cord injury symptoms seen with bilateral dislocations symptoms worsen with increasing subluxation perform thorough neruologic examination assess motor and sensory status neurologic reflexes document findings via ASIA scoring Imaging Radiographs views ap, lateral, oblique, open-mouth odontoid findings lateral shows subluxation of vertebral bodies unilateral dislocations lead to ~ 25% subluxation bilateral facet dislocation leads to ~ 50% subluxation on xray loss of disc height might indicated 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 possibility of spontaneous reduction and occult instability CT scan indications most cases require a CT scan 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 is 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 an MRI should always be performed prior to open reduction or surgical stabilization if a disc herniation is present with compression on the spinal cord, then you must go anterior to perform a anterior cervical diskectomy 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 x 6-12 weeks indications stable facet fracture unilateral reduced 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 stabililzation 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 there is no spinal cord injury so urgency is much less than with a bilateral dislocation timing emergent to obtain reduction especially when you have bilateral dislocation once reduction is obtain, and patient 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 dislocation are easier to reduce (PLL torn) but less stable following reduction outcomes 26% of patients will fail closed reduction and require open reduction unilateral facet dislocations 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 is failed, may attempt open reduction from anterior approach by distracting across casper pins with simulatenous rotation 1-level interbody arthrodesis with anterior plating posterior reduction & instrumented stabilization indications when no anteior 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 can not be reduced through closed or open anterior technique emergent MRI then emergent open reduction surgical stabilization indications facet dislocations (unilateral or bilateral) in patient 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 then you must use an anterior approach and do a discectomy Techniques Halo external immobilization technique halo is suboptimal in lower cervical spine and therefore hard orthosis may be satifactory 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 to 10 lbs increments can add up to 140 lbs of weight or 70% body weight average weigh required for reduction ~9.4 to 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 be 10-15 lbs and apply an extension moment to the cervical spine adjusting pulley system placing pad underneath thorax perform serial neurologic exams and plain radiographs after addition of each weight addition abort if there is over distraction of the spinal segment >1.5 times that if the adjacent uninjured disc space can switch to carbonfiber 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 diskectomy and fusion +/- open reduction indications facet dislocations reduced through closed methods with a MRI showing cervical disc herniation with significant compression on the spinal cord unilateral facet dislocations that fail closed reduction with a disc herniation with 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 are 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 currette alternatively, lamina spreaders applied to the endplates not effective for reducing bilateral facet dislocations pros and cons overdistraction of the disc space often the PLL and posterior ligaments are disrupted excessively large graft may be used to obtain a press-fit interbody graft will demonstrate the facet joints being gapped posteriorly places hardware at risk for failure over distraction also has risk of added 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 difficult reductions distraction of the affected level between the affected spinous processes or lamina with use of lamina spreaders usually have to fuse two levels due to inadequate lateral mass purchase at level of dislocation Combined anterior decompression and posterior reduction / stabilization technique go anterior first, perform discectomy, position plate but only fix plate to superior vertebral body this way 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 diskectomy, reduction, and interbody fusion Respiratory complications ARDS higher risk in the multitraumatized patient pneumonia due to prolonged recumbency and need to 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 throacic surgeon upon identification Pin tract infections associated with Halo vest immobilization can result in decreased pin purchase rarely result in meningitis if ther 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