Summary Atlas fractures and transverse ligament injuries are traumatic injuries usually caused by high-energy trauma with axial loading in young patients (Jefferson fracture) or low-energy falls in the elderly. Due to the capacious nature of the spinal canal at this level, these injuries usually present with neck pain without neurological deficits Diagnosis is often missed with plain radiographs, so a CT scan may be required to make the diagnosis. An open-mouth odontoid radiograph is useful to evaluate for disruption of the transverse ligament, which leads to lateral displacement of the lateral masses relative to one another Stable injuries can be treated with immobilization in a cervical collar. Unstable injuries require either halo-vest immobilization or surgical stabilization with fusion Epidemiology Incidence ~7% of cervical spine fractures atlas fractures comprise 25% of the injuries of the craniovertebral junction 1-3% of all spinal injuries commonly missed due to inadequate imaging of occipitocervical junction Demographics bimodal age distribution early adulthood (20-30 y/o) login to view 1 more bullet elderly login to view 5 more bullets ETIOLOGY Pathophysiology mechanism most commonly associated with high-energy injuries login to view 1 more bullet ground level falls in elderly patients login to view 1 more bullet injury biomechanics login to view 15 more bullets Associated conditions spine fracture 50% have an associated spine injury 40% associated with axis fracture closed head injuries neurologic injury risk of neurologic injury is low due to large space for the spinal cord at this level injuries tend to increase the area available for spinal cord at C1 Anatomy Bony anatomy atlas osteology atlas (C1) is a ring containing 2 articular lateral masses login to view 9 more bullets Ligamentous anatomy occipitocervical junction and atlantoaxial junction are coupled intrinsic ligaments are located within the spinal canal and provide most of the ligamentous stability. They include: transverse ligament login to view 3 more bullets paired alar ligaments login to view 2 more bullets apical ligament login to view 2 more bullets tectorial membrane login to view 1 more bullet Articulations atlanto-occipital joint (occiput-C1) occipital condyles articulate with C1 superior articular processes login to view 1 more bullet true synovial joint login to view 1 more bullet atlantoaxial joints (C1-2) facet joints login to view 2 more bullets atlanto-odontoid joint login to view 3 more bullets Classification Landells Classification for Atlas Fractures Type 1 Isolated anterior or posterior arch fractureMost common injury pattern"Plough" fracture is an isolated anterior arch fracture caused by a force driving the odontoid through the anterior archStable injuryTreat with hard collar Type 2 Jefferson burst fracture with bilateral fractures of anterior and posterior arch resulting from an axial loadStability determined by the integrity of transverse ligamentIf intact, treat with a hard collarIf disrupted, halo vest (for bony avulsion) or C1-2 fusion (for intrasubstance tear). See Dickman classification below Type 3 Unilateral lateral mass fractureStability determined by the integrity of the transverse ligamentIf stable, treat with a hard collarIf unstable, halo vest Dickman Classification for Transverse Ligament Injuries Type 1 Intrasubstance tear Treat with C1-2 fusion Type 2 Bony avulsion at tubercle on C1 lateral massTreat with halo vest (successful in 75%) Presentation History high-energy injury MVC fall from ladder ground level fall elderly patients Symptoms neck pain cervical spinal muscle spasms limited neck motion C2 neuralgia/palsy occipital neuralgia occipital numbness occipital alopecia (rare) vertebral artery dissection loss of consciousness double vision vertigo Physical exam neurologic deficits uncommon in isolated C1 fractures associated C2 fractures have a higher risk of neurologic deficit vertebral artery injury vertigo diplopia blindness ataxia bilateral weakness dysphagia nausea C2 nerve palsy decreased sensation in the occipital region neck flexion and extension weakness Imaging Radiographs recommended views lateral oblique login to view 1 more bullet open-mouth odontoid login to view 1 more bullet optional views flexion-extension login to view 1 more bullet findings increased widening of C1 lateral masses compared to C2 (lateral mass displacement (LMD)) increased distance of the atlantodental interval (ADI) fracture involving the posterior or anterior arch concomitant spine injuries login to view 3 more bullets measurements atlantodental interval (ADI) login to view 4 more bullets sum of lateral mass displacement (LMD) login to view 2 more bullets retropharyngeal soft tissue login to view 2 more bullets sensitivity radiographs have a lower sensitivity of detecting unstable atlas fractures than CT and MRI CT indications every case of suspected cervical spine injury login to view 1 more bullet good study to assess for pseudospread of the atlas in pediatric patients login to view 3 more bullets views sagittal reconstructions login to view 1 more bullet axial reconstructions login to view 1 more bullet coronal reconstructions login to view 1 more bullet angiogram login to view 1 more bullet findings fractures involving the anterior and posterior ring lateral mass fractures increased radial displacement of the C1 fracture fragments (unstable) bone avulsion injuries of the tubercle (TAL insertion) sagittal split fractures of the lateral mass sensitivity highly sensitive at detecting fractures lower sensitivity than MRI at detecting TAL injuries MRI indications any case there is a confirmed fracture of the atlas to rule out associated unstable ligamentous injuries views sagittal and coronal views login to view 1 more bullet findings TAL injuries login to view 1 more bullet spinal cord injury login to view 4 more bullets prevertebral soft tissue swelling login to view 1 more bullet more sensitive at detecting injury to transverse ligament increased T2 signal intensity in the TAL is suggestive of injury Treatment Nonoperative hard collar vs. halo immobilization for 6-12 weeks indications login to view 4 more bullets technique login to view 8 more bullets Operative posterior C1-C2 fusion vs. occipitocervical fusion indications login to view 8 more bullets technique login to view 1 more bullet C1 internal fixation indications login to view 2 more bullets preserves C1-2 motion technique login to view 2 more bullets further randomized trials are needed to ascertain the role of this treatment Techniques Posterior C1-C2 fusion preserves motion compared to occipitocervical fusion fixation C1 lateral mass to C2 pedicle screw construct (Harms' technique) login to view 2 more bullets C1-2 transarticular screw placement sublaminar wiring login to view 2 more bullets Occipitocervical fusion (occiput-C2) used when unable to obtain adequate purchase of C1 (comminuted C1 fracture) leads to significant loss of motion fixation occipital plate C1 lateral mass screws C2 pedicle screws C1 internal fixation anterior and posterior approaches described standard posterior approach fixation plate and screw construct screw and rod construct screws alone Complications Vertebral artery injury rare complication with displaced posterior ring fractures fractures involving the sulcal groove Neurologic injury rare in isolated atlas fractures radial displacement of fracture can compromise surface area of the spinal canal Cock Robin deformity displaced unilateral sagittal split lateral mass fracture occipital condyle settles onto the C2 superior articular facet treat with occipitocervical fusion +/- osteotomy to correct the deformity Nonunion ~20% of cases treated nonoperatively Neck pain present in 20-80% of patients after immobilization Delayed C-spine clearance higher rate of complications in patients with delayed C-spine clearance; important to clear expeditiously Pseudoarthrosis Stiffness loss of ~50% of cervical rotation with C1-2 arthrodesis loss of ~50% cervical flexion with occiput-C2 arthrodesis Infection a complication of surgical treatment higher infection rates in patients treated with posterior approach Prognosis Natural history with conservative treatment 8-20% report neck stiffness 14-80% report neck pain ~34% report activity limitations contact athletes may not return to play Prognostic variables stability dependent on degree of injury and healing potential of transverse ligament worse long-term patient reported outcomes in fractures with >7 mm of displacement