How Does the Anterior Maxillary Arch Change After Unilateral Lip Repair? A Systematic Review and Meta-Analysis

Objective This systematic review and meta-analysis aimed to quantify morphological changes in the anterior maxillary arch—specifically anterior cleft width (CW) and anterior curvature angle (ACA)—following primary lip repair in children with unilateral cleft lip and palate (UCLP). Methods A comprehensive search of PubMed, Google Scholar, DOAJ, and the Cochrane Library was conducted through January 2025. Eligible studies reported quantitative pre- and post-operative data on anterior arch morphology. Pooled effect sizes were calculated using a random-effects model with the Knapp–Hartung adjustment. Meta-regression assessed the influence of baseline cleft width and follow-up duration. Results Ten studies comprising 11 patient cohorts and 265 participants met the inclusion criteria. The pooled mean difference in anterior CW) was −6.217 mm (95% confidence interval (CI): −7.230 to −5.204; P < .001), with substantial heterogeneity ( I ² = 81.8%). Meta-regression identified initial cleft width as a significant predictor ( β = −0.842; P = .002), and follow-up duration showed a borderline association ( β = −0.387; P = .051). The predictive equation was: CW(change) = 4.465 − 0.842 × initial width − 0.387 × duration. Lip repair also reduced the anterior curvature angle (MD = −14.66°; 95% CI: −19.62 to −9.7), though heterogeneity was very high ( I ² = 88.1%). Conclusion Primary lip repair significantly improves anterior arch dimensions in children with UCLP. Initial cleft width predicts postoperative changes, and the proposed model may support early treatment planning. However, due to substantial heterogeneity across studies, small sample sizes in some included cohorts, and very low certainty of evidence for both outcomes (GRADE approach), the findings should be interpreted with caution and considered exploratory.