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 motor vehicle accident fall from height low-energy trauma to head/neck occasionally seen after ground level falls in the elderly due to direct blow to the skull pathoanatomy fracture patterns are dependent on the directional forces applied to the craniocervical junction at the time of the injury axial compression horizontal sheer due to a direct blow on the skull rotation lateral bending Associated injuries orthopaedic manifestations spinal cord injuries in 31% of cases neurological deficits may be acute (63%) or delayed (37%) 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 each occiput articulates with a shallow dish-like joint on the superior aspect of the lateral mass of C1 joint morphology allows for large range of flexion and extension of craniocervical junction ligamentous stability provided by a combination of atlantooccipital joint capsule alar ligaments (dens to each occipital condyle) Ligaments intrinsic ligaments are located within the spinal canal and provide most of the ligamentous stability. They include: transverse ligament primary stabilizer of atlantoaxial junction connects the posterior odontoid to the anterior atlas arch, inserting laterally on bony tubercles paired alar ligaments connect the odontoid to the occipital condyles relatively strong and contribute to occipitocervical stability apical ligament relatively weak midline structure runs vertically between the odontoid and foramen magnum tectorial membrane connects the posterior body of the axis to the anterior foramen magnum and is the cephalad continuation of the PLL 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 an anatomic complex that provides stability and function of craniocervical junction (occiput to C2) includes 6 articulations 2 atlantooccipital joints 2 paired lateral C1-C2 facets/joints 1 dens-anterior arch of C1 articulation 1 posterior midline atlantoaxial joint 3 ligamentous structures connect C2 directly to base of skull (thereby skipping C1) apical ligament alar ligament tectorial membrane 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 limited cervical ROM may elicit pain neurologic extremity exam rectal exam lower cranial nerve exam deficits most commonly affect CN IX, X, and XI 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 used to diagnosis occipitocervical dislocation C-D: distance from basion to posterior arch A-B: distance from anterior arch to opisthion significance ratio of ~1 is normal ratio >1.0 raises concern for anterior dislocation ratio <1.0 raises concern for posterior dislocation odontoid fractures ring of atlas fractures O-C2 angle angle between McGregor line and C2 significance needs to be established prior to OC fusion to prevent postoperative dysphagia that can result from a significant change in the O-C2 angle C2-T1 lordotic alignment CT indications diagnostic method of choice usually obtained as routine imaging in high-energy trauma patients clinical criteria motor paresis lower cranial nerve paresis impaired craniocervical junction motion occipital pain and tenderness altered consciousness views must include cranial-cervical junction with thin-section technique findings occiput fracture may see migration of fragment into spinal canal 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 vast majority of low energy fractures type 1 and 2 type 3 without overt instability modalities semi-rigid or rigid cervical collar usually worn for 6 weeks Operative occipitocervical fusion indications very rarely indicated type 3 with overt instability neural compression from displaced fracture fragment associated atlantooccipital or atlantoaxial injuries Techniques Occipitocervical fusion approach posterior midline incision with patient in prone position Mayfield retractor used to obtain proper craniocervical alignment establish preoperative O-C2 angle with lateral fluoroscopy prior to draping 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 posterior segmental instrumented fusion is usually performed from the occiput to C3 occipital occipital plates usually allow for 3 or 4 total screws with adjustable rod holders occipital screws usually unicortical to avoid injury to venous sinus major dural venous sinuses are located just below the external occipital protuberance and are at risk of penetrative injury some institutions prefer bicortical screws, but they come at increased risk occipital screw safe zone the safe zone for occipital screws is located within an area measuring 2 cm lateral and 1 cm inferior to the external occipital protuberance along the superior nuchal line C1 lateral mass screws often skipped due to the angle at base of skull making it more difficult to place a rod may choose a unilateral screw to provide some rotational stability for the C1 ring C2 fixation pars, pedicle, transarticular, or translaminar screws C3 fixation standard lateral mass screws aimed cephalad and lateral to avoid vertebral artery 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