The 6-year-old brother (patient 2) of the 9-year-old female patient was also a restrained backseat passenger in the same vehicle involved in the MVA. The patient was placed in a cervical immobilization device and transported to the ED. His initial assessment revealed a Glasgow Coma Scale score of 15.
Cervical CT examination revealed the following normal values: an atlanto-occipital junction width of 3.83 mm, an interspinous ratio of 2.14, SAC of 20.05 mm, a BDI of 8.76 mm, the normal Wackenheim line, a Powers ratio of 0.79, a CCI of 3.21 mm, and an atlanto-dens interval (ADI) of 2.47 mm (Table 1).
MRI of the cervical spine revealed the tectorial membrane as intact, although elevated by retroclival hematoma (Figure 4, A). There was no evidence of severe posterior ligamentous injury. The injury was thought to be treatable with a neck brace.
MRI of the brain 5 days after the MVA revealed that the hematoma in the retroclival region was improved, with reduction in the elevation of the tectorial membrane compared with the previous study (Figure 4, B). The patient was discharged with a neck brace in stable condition. At the 2-week follow-up, the patient had developed a right, lateral gaze palsy, which resolved in 4 months. At the 3-month follow-up, he lacked 20% of lateral rotation to the left. At the 5-month follow-up, physical examination revealed normal rotation and flexion of the neck. He was instructed to remove his cervical collar and given permission to resume physical activities. Cervical flexion and extension radiographs at the 1- and 2-year follow-up periods revealed no OC instability and normal alignment.
The youngest sibling (patient 3), a 5-year-old brother of the aforementioned children, was a restrained backseat passenger in the same vehicle involved in the MVA. This child was killed during the accident. The autopsy report obtained from the trauma service revealed that he died with OC dissociation.
A delay in the diagnosis and stabilization of OC dissociation can result in secondary neurologic injury, as well as increased morbidity and mortality.11,12 With advances in imaging modalities, physicians now use several CT measurement techniques of the cervical spine, each with its own drawbacks, to identify OC dissociation. Such methods include the BDI, atlanto-occipital junction width, Wackenheim line, Powers ratio, interspinous ratio, ADI, and SAC. A more recent method, the CCI, was described by Pang et al10 as having 100% sensitivity and specificity for OC dissociation.
Several classification systems have been proposed to help physicians decide between nonsurgical management and surgical fixation. In 2003, Steinmetz et al13 described a system using MRI to grade OC dissociation. The injury is deemed either grade I (incomplete) or grade II (complete) depending on the integrity of the tectorial membrane. Steinmetz grade I injuries can be managed nonsurgically, whereas Steinmetz grade II injuries require surgical fixation. Astur et al14 proposed using surgeon-supervised flexion/extension/distraction imaging with live lateral fluoroscopy when physicians are unable to assess the extent of ligamentous injury via both CT and MRI evaluation.
In 2007, Horn et al15 proposed a grading system using both CT and MRI. Grade I injuries have normal CT measurements, such as the Powers ratio and other previously mentioned methods, but they do have moderately abnormal findings on MRI (high posterior ligaments or edema in OC joints). Grade II injuries have at least one abnormal finding on the established CT diagnostic criteria or exhibit grossly abnormal MRI findings in the atlanto-occipital joints, tectorial membrane, alar or cruciate ligaments. Grade I injuries qualify for nonsurgical management, whereas grade II injuries warrant surgical fixation.
In our study, patient 1 sustained a Steinmetz grade II injury; MRI showed significant tectorial membrane disruption. Furthermore, according to the Horn classification system, patient 1 sustained a grade II injury (abnormal CT measurements of a 7.2-mm mean atlanto-occipital joint width, an interspinous ratio of 2.75 mm, and SAC of 15.81 mm, as well as significant MRI findings of an evolving retroclival and anterior upper cervical epidural hematoma, with a torn tectorial membrane and apical ligament). In light of these radiographic findings, patient 1 underwent occiput-to-C2 posterior spinal fusion with instrumentation and harvest of right iliac crest bone graft. At the 2-year follow-up, she showed no evidence of OC instability, maintained 50% of her neck rotation and lateral bending, and had an entirely normal neurologic examination.
Patient 2 sustained a Steinmetz grade I injury; MRI revealed a mildly elevated but intact tectorial membrane. His injury was deemed a Horn grade I injury (no abnormal CT measurements and moderate MRI abnormalities revealing a retroclival hematoma without additional evidence of ligamentous injury). The literature reports only a limited number of patients with OC dissociation were successfully treated nonsurgically.16 Patient 2 was successfully treated with a neck brace for 5 months, resuming normal activities thereafter. At the 2-year follow-up, he showed no evidence of OC instability, had no deficits in his cervical spine range of motion, and had an entirely normal neurologic examination.
Posterior OC fusion is usually performed in patients with OC instability.14,17,18 Bone graft, usually harvested from the iliac crest, as was performed on patient 1, is commonly used. Because children are more commonly presenting with OC dissociation in the inpatient setting, physicians must be prepared to successfully manage this previously unsalvageable injury.
The measurements collected from our two patients, the mean AO joint width, the interspinous ratio, and SAC measurement indicated OC dissociation in the older sister. The Powers ratio, BDI, and Wackenheim line were all within normal limits. Of note, the CCI was also within normal limits for both of our patients. However, on MRI evaluation, OC dissociation was observed in both living siblings, and severe ligamentous injury was noted in the older sister. In comparison, despite an elevated tectorial membrane, the younger brother's MRI did not reveal the torn ligaments seen in his sister's case. This occurrence demonstrates the inaccuracies of the various CT measuring techniques used for the diagnosis of OC dissociation. The CT measurement methods may prove useful when determining the injury grade based on the classifications proposed by Steinmetz et al13 and Horn et al.15 However, in the setting of clinically suspected OC dissociation with normal CT measurements, we recommend obtaining a cervical spine MRI to properly assess the extent of ligamentous injury. The successful treatment of our two patients supports the treatment recommendations proposed by these grading systems. The injuries sustained by these three siblings during the same MVA—ranging from moderate, requiring conservative management; severe, requiring surgical intervention, and fatal—further highlight the spectrum of disease observed in OC dissociation.
1. Blackwood NJ: III. Atlo-occipital dislocation: A case of fracture of the atlas and axis, and forward dislocation of the occiput on the spinal column, life being maintained for thirty-four hours and forty minutes by artificial respiration, during which a laminectomy was. Ann Surg 1908;47:654–658.
2. Houle P, McDonnell DE, Vender J: Traumatic atlanto-occipital dislocation in children. Pediatr Neurosurg 2001;34:193–197.
3. Astur N, Klimo P, Sawyer JR, Kelly DM, Muhlbauer MS, Warner WC: Traumatic atlanto-occipital dislocation in children: Evaluation, treatment, and outcomes. J Bone Joint Surg Am 2013;95:e194(1-8).
4. Shamoun JM, Riddick L, Powell RW: Atlanto-occipital subluxation/dislocation: A “survivable” injury in children. Am Surg 1999;65:317–320.
5. Kaufman RA, Carroll CD, Buncher CR: Atlantooccipital junction: Standards for measurement in normal children. Am J Neuroradiol 1987;8:995–999.
6. Sun PP, Poffenbarger GJ, Durham S, Zimmerman RA: Spectrum of occipitoatlantoaxial injury in young children. J Neurosurg 2000;93(1 suppl):28–39.
7. Deliganis AV, Mann FA, Grady MS: Rapid diagnosis and treatment of a traumatic atlantooccipital dissociation. AJR Am J Roentgenol 1998;171:986.
8. Mazzara JT, Fielding JW: Effect of C1-C2 rotation on canal size. Clin Orthop Relat Res 1988:115–119.
9. Kuzma B, Goodman J: Diagnosis of atlanto-occipital dislocation. Surg Neurol 1997;48:418–419.
10. Pang D, Nemzek WR, Zovickian J: Atlanto-occipital dislocation: Part 1: Normal occipital condyle-C1 interval in 89 children. Neurosurgery 2007;61:514–521, discussion 521.
11. Kalani MA, Ratliff JK: Considering the diagnosis of occipitocervical dissociation. Spine J 2013;13:520–522.
12. Rasool MN, Govender S: Traumatic dislocation of the atlanto-occipital joint. S Afr Med J 1987;72:295.
13. Steinmetz M, Lechner R, Anderson J: Atlantooccipital dislocation in children: Presentation, diagnosis, and management. Neurosurg Focus 2003;14:1–7.
14. Astur N, Sawyer JR, Klimo PJ, Kelly DM, Muhlbauer M, Warner WCJ: Traumatic atlanto-occipital dislocation in children. J Am Acad Orthop Surg 2014;22:274–282.
15. Horn EM, Feiz-Erfan I, Lekovic GP, Dickman CA, Sonntag VKH, Theodore N: Survivors of occipitoatlantal dislocation injuries: Imaging and clinical correlates. J Neurosurg Spine 2007;6:113–120.
16. Kaplan NB, Molinari C, Molinari RW: Nonoperative management of craniocervical ligamentous distraction Injury: Literature review. Globe Spine J 2015;5:505–512.
17. Vender JR, Rekito AJ, Harrison SJ, McDonnell DE: The evolution of posterior cervical and occipitocervical fusion and instrumentation. Neurosurg Focus 2004;16:E9.
Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons
18. Bellabarba C, Mirza SK, West GA, et al: Diagnosis and treatment of craniocervical dislocation in a series of 17 consecutive survivors during an 8-year period. J Neurosurg Spine 2006;4:429–440.