C1-C2 fusion with absence of C1 posterior arch and presence of C2 high-riding vertebral artery: Is it possible?

The presence of anatomical anomalies such as absence of C1 posterior arch and presence of C2 high-riding vertebral artery may not allow a conventional C1-C2 fusion, and this patient will require occipitocervical fusion. A 62-year-old lady presented with cervical myelopathy. CT scan demonstrated an os odontoideum with C1-C2 dislocation. The posterior arch of atlas on right C1 vertebra was absent, and there was high-riding vertebral artery on left C2. MRI revealed severe cord compression with cord oedema. The chronic atlantoaxial dislocation was reduced successfully with skeletal traction. Hybrid C1-C2 fusion augmented with autogenous local bone graft with corticocancellous iliac crest bone graft was performed to avoid an unnecessary occipitocervical fusion. She was stable throughout surgery and discharged 6 days later. CT scan 6 months post-operation showed a solid posterior fusion mass. Hybrid C1-C2 fusion can be performed to avoid occipitocervical fusion despite presence of abnormal anatomy at C1 and C2 vertebrae.