Impact of interlaminar graft materials on the fusion status in atlantoaxial transarticular screw fixation

Abstract

Object. Structural interlaminar graft materials were used for atlantoaxial transarticular screw fixation (TSF), and its impact on the fusion status was investigated. Methods. Forty-two patients (10 men, 32 women, mean age 51 years, mean follow-up period 45 months; 30 with rheumatoid arthritis, and 12 with os odontoideum) underwent TSF and modified Brooks posterior wiring involving titanium cables. As interlaminar graft materials, autologous bone from posterior iliac crest alone was used in 20 patients (Group A), and a structural spacer (13 ceramic spacers, nine titanium mesh cages) in 22 (Group B). Lateral radiographs were evaluated to determine bone fusion, alignment of the cervical spine, and wire loosening. Solid osseous fusion was obtained in 95% of Group A and 96% of Group B patients. The mean atlantoaxial angle was 19.1 ± 9.7° and 16.7 ± 10.4° before surgery (p = 0.45), and 27.4± 7.8° and 22.1 ± 5.5° after surgery (p = 0.02) in Groups A and B, respectively. Atlantoaxial hyperlordosis (atlantoaxial angle ≥ 30°) was observed in 32% of Group A and 18% of Group B patients (p = 0.26). Postoperative kyphosis occurred in 40% of Group A and 23% of Group B patients (p = 0.28). Loosening of the cable was demonstrated in 50% of Group A and 36% of Group B patients (p = 0.37). In Group B patients maintenance of cervical lordosis was more likely than in those in Group A, although the differences did not reach statistical significance. Conclusions. These results indicate that structural interlaminar spacers can maintain proper cervical alignment without a decease in the fusion rate; the authors recommend their use in conjunction with TSF.