Post atlantoaxial fusion for unilateral cleft of atlas posterior arch associated with os odontoideum: case report and technique note.

A case of a 34-year-old female with unilateral cleft of atlas posterior arch associated with os odontoideum is reported. The patient had experienced neck pain for 6 months. Five days earlier to admission the pain aggravated as a result of mild head trauma from behind. Imaging examinations revealed C1-2 subluxation as well as the deformity. After 3 days of skull traction, a sound C1-2 reduction was achieved. Post atlantoaxial fusion using bilateral transarticular screws combined with C1 laminar hook on the intact side and autogenous bone graft was performed. On the sixth month of postoperative follow-up, CT revealed solid fusion was achieved. No related complications were detected within 3 years of follow-up. The clinical manifestations and imaging findings were presented. The incidence and etiopathogenesis of hypoplastic posterior arch of the atlas were concisely introduced. Techniques of post atlantoaxial fusion under circumstances of unilateral C1 posterior elements defects were discussed. The authors believe bilateral transarticular screws combined with C1 laminar hook on the intact side and autogenous bone graft can be applicable to atlantoaxial fusion on the premise of preoperative C1-2 reduction and C1 posterior arch remaining >1/2 of its full length.