Study Design: Literature review and meta-analysis.
Objective: To compare clinical and radiographic outcomes of patients treated with transarticular screws (TASs) and screw-rod constructs (SRCs) for posterior atlantoaxial fusion.
Background: Modern techniques for C1–C2 fusions include Magerl and Seeman’s TAS and SRC using C1 lateral mass screws and C2 pars/pedicle screws as described by Goel and Laheri and later modified by Harms and Melcher.
Materials and Methods: Online databases were searched for English-language articles between 1986 and April 2011 describing posterior atlantoaxial instrumentation with C1–C2 TAS or SRC. Forty-five studies (2073 patients) treated with TAS and 24 studies (1073 patients) treated with SRC fulfilled inclusion criteria. Standard and formal meta-analysis techniques were used to compare the outcomes.
Results: All studies provided class III evidence. There were no differences in 30-day mortality (0.8% vs. 0.6%) or neurological injury (0.2% vs. 0%). There was a higher incidence of vertebral artery injury [4.1% (95% confidence interval (CI), 2.8%–5.4%) vs. 2.0% (95% CI, 1.1%–3.4%); P=0.02] and malpositioned screws [7.1% (95% CI, 5.7%–8.8%) vs. 2.4% (95% CI, 1.1%–4.1%); P<0.001] and a slightly lower rate of fusion with the TAS technique [97.5% (95% CI, 95.9%–98.5%) vs. 94.6% (95% CI, 92.6%–96.1%); P<0.001].
Conclusions: TAS and SRC are safe and effective treatment options for C1–C2 instability but require a thorough knowledge of atlantoaxial anatomy for successful insertion of screws. Slightly higher rates of fusion and less risk of injury to the vertebral artery during screw placement were observed with the SRC technique. However, differences in graft material and techniques were noted. Prospective, randomized studies with validated radiographic and clinical outcome metrics are necessary for proper comparison of these techniques.