Summary Occipital condyle fractures are traumatic injuries that involve the articulation between the base of the skull and the cervical spine Diagnosis is best made with a CT scan. An MRI and/or flexion-extension radiographs are used to evaluate for associated occipitocervical instability Most fractures are treated with immobilization using a cervical orthosis. Occipitocervical fusion is indicated in rare cases where occipitocervical instability is present Epidemiology Incidence relatively uncommon ~1-3% of population with blunt craniocervical trauma often missed due to low sensitivity of plain radiographs reported incidence is increasing due to increased utilization of CT scans ETIOLOGY Pathophysiology occipital condyle fractures represent a subset of basilar skull fractures mechanism high-energy trauma to the head/neck login to view 2 more bullets low-energy trauma to head/neck login to view 1 more bullet pathoanatomy fracture patterns are dependent on the directional forces applied to the craniocervical junction at the time of the injury login to view 4 more bullets Associated injuries orthopaedic manifestations spinal cord injuries in 31% of cases login to view 1 more bullet cervical fracture vertebral artery injury polytrauma medical manifestations intracranial bleeding brainstem and vascular lesions elevated ICP Anatomy Osteology occipital condyle morphology occipital condyles are paired oval prominences of the occipital bone form the lateral aspects of the foramen magnum atlantooccipital joint (occiput-C1) articulation login to view 2 more bullets ligamentous stability login to view 3 more bullets Ligaments intrinsic ligaments are located within the spinal canal and provide most of the ligamentous stability. They include: transverse ligament login to view 2 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 Vascular system occipital condyles are in proximity to vertebral arteries Nervous system occipital condyles are in close proximity to: medulla oblongata spinal cord lower cranial nerves (CN IX-XII) C2 nerve root Biomechanics occipitoatlantoaxial complex (craniocervical junction) function login to view 1 more bullet includes 6 articulations login to view 4 more bullets 3 ligamentous structures connect C2 directly to base of skull (thereby skipping C1) login to view 3 more bullets Classification Anderson and Montesano Classification Type I 3% of occipital condyle fractures Impaction-type fracture with comminution of the occipital condyle Due to compression between the atlantooccipital joint Stable injury due to minimal fragment displacement into the foramen magnum Type II 22% of occipital condyle fractures Basilar skull fracture that extends into one or both occipital condyles Due to a direct blow to skull and a sheer force to the atlantooccipital joint Stable injury as the alar ligament and tectorial membrane are usually preserved Type III 75% of occipital condyle fractures Avulsion fracture of condyle in region of the alar ligament attachment (suspect underlying occipitocervical dissociation) Due to forced rotation with combined lateral bending Has the potential to be unstable due to craniocervical disruption Presentation History clinical presentation is highly variable often a history of high-energy trauma with associated head injury (possible vertebral artery injury, spinal cord injury) Symptoms high cervical pain neck stiffness double vision upper and lower extremity weakness Physical examination inspection look for trauma to skull (e.g. skull laceration) ROM remove collar and evaluate limited motion login to view 1 more bullet neurologic extremity exam rectal exam lower cranial nerve exam login to view 1 more bullet Imaging Radiographs recommended views AP, lateral, and open-mouth AP view alternative views flexion and extension views findings diagnosis rarely made on plain radiographs due to superimposition of structures (maxilla and/or occiput) blocking view of occipital condyles open-mouth AP view may depict occipital condyle injuries measurements Powers ratio = C-D/A-B login to view 10 more bullets O-C2 angle login to view 3 more bullets C2-T1 lordotic alignment CT indications diagnostic method of choice usually obtained as routine imaging in high-energy trauma patients clinical criteria login to view 5 more bullets views must include cranial-cervical junction with thin-section technique findings occiput fracture login to view 1 more bullet joint diastasis (2 mm or less is considered normal) CT angiogram indications concern for vertebral artery injury surgical planning to identify location of vertebral artery MRI indications evaluation of soft-tissue craniocervical trauma spinal cord or brain stem ischemia findings edema or fluid collection in the atlantooccipital joint (representing rupture of the atlantooccipital joint capsule) edema or fluid collection consistent with avulsion injury of alar ligament from dens or occiput Magnetic resonance angiogram (MRA) indications consider with suspected vascular injury Differential Key differential occipitocervical instability atlas fracture odontoid fracture Treatment Nonoperative immobilization with cervical orthosis indications login to view 3 more bullets modalities login to view 2 more bullets Operative occipitocervical fusion indications login to view 4 more bullets Techniques Occipitocervical fusion approach posterior midline incision with patient in prone position Mayfield retractor used to obtain proper craniocervical alignment login to view 1 more bullet deep dissection if performing C1 lateral mass screw fixation, work within safe zone and do not dissect above the posterior arch of C1 more than 1 cm lateral to midline to avoid injury to vertebral artery instrumentation length login to view 1 more bullet occipital login to view 7 more bullets C1 lateral mass screws login to view 2 more bullets C2 fixation login to view 1 more bullet C3 fixation login to view 1 more bullet arthrodesis perform decortication of occiput, posterior arch of C1, and lamina of C2 may require autogenous or allograft bone grafting postoperative immobilization patients frequently immobilized in halo or hard cervical orthosis for 6-12 weeks to obtain fusion Complications Nonoperative neck pain and stiffness Operative intracranial venous sinus injury (occipital screws) vertebral artery injury (C1 lateral mass screws) adjacent segment disease neck pain and stiffness Prognosis high mortality rate (11%) due to associated injuries rate has decreased due to improvement in first responder cervical spine precautions