Unfavourable splits in sagittal split osteotomy: An updated systematic review and meta-analysis

Unfavourable splits remain an important intraoperative complication of sagittal split osteotomy (SSO). We updated the evidence to quantify contemporary incidence and to reassess claims concerning third-molar status and osteotomy design. PubMed/MEDLINE and Europe PMC were searched from 13 August 2015 to 24 August 2026, and Embase was searched on 3 October 2026. Eighteen independent contemporary incidence cohorts reported 279 events among 11,159 osteotomy sites. A binomial-normal generalized linear mixed model, which required no continuity correction, estimated an incidence of 2.66% (95% confidence interval [CI] 1.71%-4.11%). Between-study heterogeneity was substantial (tau = 1.09 on the logit scale), with an approximate 95% prediction interval of 0.30%-19.66%. The crude proportion was 2.50%, compared with the published historical aggregate of 2.35% (458/19,527 sites). Third-molar studies compared clinically heterogeneous states; study-specific estimates are therefore presented without a single causal summary. For long versus short medial osteotomy, the risk ratio was 1.78 (95% CI 0.76-4.17). The evidence does not establish that third-molar timing or a particular medial-cut design prevents unfavourable splitting.