The impact of odontoid screw fixation techniques on screw-related complications and fusion rates: a systematic review and meta-analysis.

PURPOSE: The primary goal of this study was to conduct a systematic review and meta-analysis of articles focused on odontoid screw fixation (OSF) and screw-related complications or non-union rates.

METHODS: We conducted a systematic review of the PubMed and Crossref databases between January 1982 and December 2019. Inclusion criteria comprised detailed descriptions of the surgical technique and screw-related complications (screw cut-out, loosening, breakage, malposition) or fusion rates.

RESULTS: The initial selection consisted of 683 abstracts. A total of 150 full texts were chosen for detailed study, and 83 articles were included in the analysis. The point estimates for screw-related complications were as follows: 1. screw malposition frequency-4.8%; 2. screw cut-out rate-5.0%; 3. screw loosening/pull-out-3.8%; and 4. screw fracture rate-3.1%. The point estimate for the non-union rate was 9.7%. Statistical analysis of the screw-related complications rate based on surgical technique details was also performed CONCLUSIONS: Double-screw OSF performance in elder patients resulted in a higher risk of post-operative screw cut-out. In other cases, the development of screw-related complications did not depend on the method of intraoperative head fixation, selection of the implant entry point for OSF, type of the used screws, or cannulated instruments application. The outcomes of single-screw fixation through the anterior lip of the C2 vertebra were comparable to other techniques of OSF. Further, statistically reliable studies should be carried out to identify the optimal technique of OSF.