Abstract
We report a case of agenesis of the odontoid base after atlantoaxial posterior fusion.
A thirteen-year-old boy presented in 1991 with a chief complaint of gait disturbance. He had distal dominant sensory disturbance and a spastic gait.
Agenesis of odontoid base (Greenberg type III) was observed on plain radiographs. Atlantoaxial instability was apparent in the flexion position. Space available for spinal cord was 7 mm in flexion and 17 mm in extension. MRI showed severe spinal cord compression at C1/C2 level. Atlantoaxial posterior fusion (Gallie procedure) was performed in 1991, and Halo-vest was applied for two months after surgery.
Neurological deficits were not observed at the final follow up of 11 years after surgery. Lordosis of the upper cervical spine (C1 to C3) had not changed over the eleven years and the spinous processes of C1, C2 and C3 had united. Although the growth rate of C3 vertebral height was not different from the lower vertebrae, that of C2 was smaller than that of the lower vertebrae. Growth of grafted bone was also observed. A defect of the first cervical sclerotome may have contributed to the cause of smaller growth rate of C2.
