Background: Atlantoaxial dislocation (AAD) and Basilar invagination (BI) are complex craniospinal alignment pathologies with significant clinical morbidity at presentation and a potential for life threatening complications. To realign the craniospinal complex optimally various strategies have been employed over the years ranging from, transoral odontoidectomy to sublaminar wire fixation and in situ screw fixation with significant morbidity and sub-optimal outcomes. This study focuses on our experience with the current treatment strategy of C1-C2 joint distraction and fusion, in managing this complex pathology.
Purpose: To study the clinical and radiological outcome in patients with atlantoaxial instability undergoing posterior C1 lateral mass and C2 joint distraction and pedicle screw rod fixation.
Study design: Prospective clinical study with 30 patient samples.
Outcome measures: Clinical outcomes-Modified Japanese orthopaedic association (mJOA) score, Nurick’s grading for myelopathy and visual analogue scale (VAS) for pain. Radiological outcomes-Bony fusion and alignment was analyzed by X-ray and computed tomography (CT) craniovertebral junction (CVJ).
Methods: All adult and paediatric patients who were admitted to Manipal Hospital, Bengaluru (Karnataka, India) between 10-78 years of age with atlantoaxial instability and underwent posterior C1-C2 joint distraction and fixation from 2016 to 2021, comprised the study group. All patients were followed up immediately post operatively and at intervals of 3 months 6 months and 1 year. Clinical follow-up was done using the mJOA score, Nurick’s grading for myelopathy and VAS for pain. Radiological documentation of bony fusion and alignment was done by X-ray and CT CVJ.
Results: 30 patients underwent the procedure during the study period. All our patients had good clinical outcome with a statistically significant (p < 0.01) improvement in spasticity on both the mJOA and Nurick’s grading. The reduction in neck pain on the VAS was also found to be statistically significant. Correction of craniovertebral alignment was noted with, the odontoid process receded by a mean of 4.4 mm, 3.7 mm and 4.5 mm from the Chamberlain’s line, Mc Rae’s line and the Mc Gregor’s line respectively with a reduction in Atlanto-dental interval (ADI) by a mean of 4.37 mm. The change in the post-operative craniometric measurements clearly indicated a significant re-alignment of the craniovertebral junction towards baseline. None of the patients developed neurological worsening post-surgery, while 2 patients had superficial wound infection and another had an occipital pressure sore, all of which were managed conservatively.
Conclusion: C1-C2 Joint distraction-reduction-realignment is a safe and effective option to treat AAD and BI. Although this procedure has a steep learning curve, it is biomechanically stable and provides good circumferential decompression of the neural elements by a purely posterior approach.

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