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Object: The stability provided by 3 occipitoatlantal fixation techniques (occiput [Oc]-C1 transarticular screws, occipital keel screws rigidly interconnected with C-1 lateral mass screws, and suboccipital/sublaminar wired contoured rod) were compared., Methods: Seven human cadaveric specimens received transarticular screws and 7 received occipital keel-C1 lateral mass screws. All specimens later underwent contoured rod fixation. All conditions were studied with and without placement of a structural graft wired between the skull base and C-1 lamina. Specimens were loaded quasistatically using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording segmental motion optoelectronically. Flexibility was measured immediately postoperatively and after 10,000 cycles of fatigue., Results: Application of Oc-C1 transarticular screws, with a wired graft, reduced the mean range of motion (ROM) to 3% of normal. Occipital keel-C1 lateral mass screws (also with graft) offered less stability than transarticular screws during extension and lateral bending (p < 0.02), reducing ROM to 17% of normal. The wired contoured rod reduced motion to 31% of normal, providing significantly less stability than either screw fixation technique. Fatigue increased motion in constructs fitted with transarticular screws, keel screws/lateral mass screw constructs, and contoured wired rods, by means of 19, 5, and 26%, respectively. In all constructs, adding a structural graft significantly improved stability, but the extent depended on the loading direction., Conclusions: Assuming the presence of mild C1-2 instability, Oc-C1 transarticular screws and occipital keel-C1 lateral mass screws are approximately equivalent in performance for occipitoatlantal stabilization in promoting fusion. A posteriorly wired contoured rod is less likely to provide a good fusion environment because of less stabilizing potential and a greater likelihood of loosening with fatigue.

Object: Although rare, traumatic occipitoatlantal dislocation (OAD) injuries are associated with a high mortality rate. The authors evaluated the imaging and clinical factors that determined treatment and were predictive of outcomes, respectively, in survivors of this injury., Methods: The medical records and imaging studies obtained in 33 patients with OAD were reviewed retrospectively. Clinical factors that predicted outcomes, especially neurological injury at presentation and imaging findings, were evaluated. The most sensitive method for the diagnosis of OAD was the measurement of basion axial-basion dens interval on computed tomography (CT) scanning. Five patients with severe traumatic brain injuries (TBIs) were not treated and subsequently died. Of the 28 patients in whom treatment was performed, 23 underwent fusion and five were fitted with an external orthosis. Abnormal findings of the occipitoatlantal ligaments on magnetic resonance (MR) imaging, associated with no or questionable abnormalities on CT scanning, provided the rationale for nonoperative treatment. Of the 28 patients treated for their injuries, perioperative death occurred in five, three of whom had presented with severe neurological injuries. The mortality rate was highest in patients with a TBI at presentation. The mortality rate was lower in patients presenting with a spinal cord injury, but in this group there was a higher rate of persistent neurological deficits., Conclusions: The spines in patients with CT-documented OAD are most likely unstable and need surgical fixation. In patients for whom CT findings are normal and MR imaging findings suggest marginal abnormalities, nonoperative treatment should be considered. The best predictors of outcome were severe brain or upper cervical injuries at initial presentation.

The authors describe a new technique of internal atlantooccipital screw fixation involving posterior wiring and fusion for the treatment of traumatic atlantooccipital dislocation, which was performed in a 17-year-old male patient involved in a motor vehicle accident and who suffered from atlantooccipital dislocation without neurological injury. At the 6-month follow-up examination, the patient was neurologically intact with a solid occipitocervical fusion and full range of motion of the neck.

Object: The authors sought to establish radiological criteria for the diagnosis of C1-2 vertical distraction injuries., Methods: Conventional radiography, computerized tomography (CT), and magnetic resonance (MR) imaging findings in five patients with a C1-2 vertical distraction injury were correlated with their clinical history, operative findings, and autopsy findings. The basion-dens interval (BDI) and the C-1 and C-2 lateral mass interval (LMI) were measured in 93 control patients who underwent CT angiography; these measurements were used to define the normal BDI and LMI. The MR imaging results obtained in 30 healthy individuals were used to characterize the normal signal intensity of the C1-2 joint. The MR imaging results were compared with MR images obtained in five patients with distraction injuries. In the 93 patients, the BDI averaged 4.7 mm (standard deviation [SD] 1.7 mm, range 0.6-9 mm) and the LMI averaged 1.7 mm (SD 0.48 mm, range 0.7-3.3 mm). Based on CT scanning in the five patients with distraction injuries, the BDIs (mean 11.9 mm, SD 3.2 mm; p < 0.001) and LMIs (mean 5.5 mm, SD 2 mm; p < 0.0001) were significantly greater than in the control group. Fast-spin echo inversion-recovery MR images obtained in these five patients revealed markedly increased signal distributed throughout the C1-2 lateral mass articulations bilaterally., Conclusions: In 95% of healthy individuals, the LMI ranged between 0.7 and 2.6 mm. An LMI greater than 2.6 mm indicates the possibility of a distraction injury, which can be confirmed using MR imaging. Patients with a suspected C1-2 distraction injury may be candidates for surgical fusion of C1-2.

Cervical spine injuries in the pediatric population typically affect the upper cervical region. The authors present the first reported case of a subaxial C6-7 unilateral locked facet joint in a neurologically intact 10-month-old infant. To date, this patient's nonoperative treatment has been successful. The proposed biomechanical mechanism of this injury and the treatment paradigm are discussed.