SURGICAL-MANAGEMENT OF ATLANTOAXIAL NONUNIONS

Sixteen patients referred for atlantoaxial fixation failures were treated surgically with revision procedures during the past decade. Of these 16 patients, atlantoaxial instability occurred because of rheumatoid arthritis in dye, os odontoideum in seven, transverse ligament disruption in two, and odontoid fracture nonunion in two. The 16 individuals (10 men, six women; mean age 43.7 years; age range 20-77 years) had undergone a total of 20 C1-2 internal fixation procedures that failed. Surgical strategies for definitive revision of the nonunions in these 16 subjects included 10 rigid internal fixations with transarticular screws, three revised C1-2 fixations with autogenous bone struts and wire or cables, and three extended fixations with occipitocervical instrumentation. Autogenous grafts were used in all revisions. A postoperative halo brace was used in five individuals with osteoporotic bone; all patients wore a restrictive postoperative cervical orthosis. Postoperatively, 15 patients (94%) had a stable construct (mean follow up 35 months; range 12-79 months), which included 13 osseous unions and two stable fibrous unions. One patient had nonunion; he fractured his anterior C1-2 transarticular screws 2 years postoperatively. He had occipital radicular pain without myelopathy but refused further surgery. Atlantoaxial pseudarthroses were effectively treated by addressing the pathological, biomechanical, and technical reasons for failed fusion. Successful fusion after reoperation was improved by using autologous bone grafts, adequately controlling atlantoaxial motion (with rigid transarticular screws internally or externally with a halo vest), compressing the bone grafts between the arches of C-1 and C-2 with wire cables, meticulously preparing the fusion bed, and by optimizing the pharmacological and clinical parameters to promote bone healing.