Supraclavicular Foramina in Dry Clavicles: An Observational Study and Meta-Analysis of Prevalence and Laterality

Background: The supraclavicular foramen (SCF) is a rare anatomical variant formed when a branch of the supraclavicular nerve traverses the clavicle through a complete transclavicular canal. Published studies differ substantially in study material, denominators, and reporting of side-specific and bilateral data, so bilateral anatomy is often synthesized as if pairing were irrelevant. Objectives: This study aimed to describe SCF in a Greek osteological sample and to apply a meta-analytic framework distinguishing per-clavicle prevalence, marginal laterality, paired laterality, and separately observed bilateral prevalence. Methods: We examined 115 dry clavicles of Greek origin for SCF frequency, size, and topography. Measurements were obtained independently by four observers using stainless-steel wires and digital calipers, with inter-rater agreement assessed by intraclass correlation coefficients. A systematic review and meta-analysis were then conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. PubMed, Scopus, and SciELO were searched from inception to 11 April 2026, supplemented by Google Scholar and backward and forward citation tracking, without language restrictions. Quantitative synthesis included pooled per-clavicle prevalence, conventional marginal left-versus-right comparison, and feasibility-based paired laterality analysis under explicit dependence assumptions when bilateral information was incomplete. Observed bilateral prevalence was analyzed separately using only studies with directly reported body-level bilateral counts. Risk of bias in the included studies was assessed using the Anatomical Quality Assessment tool, while the review itself was appraised using the Critical Appraisal Tool for Anatomical Meta-Analysis. Results: Complete transclavicular canals, identified by two external openings connected by a complete transosseous passage, were present in 3/115 clavicles (2.6%), with a mean aggregate transverse wire span of 1.5 ± 0.8 mm and a mean relative acromial position of 0.44 ± 0.01. Inter-rater reliability was excellent. Pooled per-clavicle prevalence was 2.2%, with 95% confidence intervals (CIs) 1.4–3.0% and I2 = 71%. Conventional marginal laterality supported left-sided predominance, with an odds ratio of 1.76 (95% CI: 1.16–2.66; I2 = 0%), while feasibility-based paired laterality yielded a stronger effect (paired OR = 2.26, 95% CI: 1.30–3.94). The main observed bilateral-prevalence model yielded 0.95% (95% CI: 0.33–2.70%). The Doi plot and Luis Furuya-Kanamori index indicated minor asymmetry. Conclusions: Complete transclavicular canals occurred in 2.6% of the examined clavicles and occupied a reproducible mid-to-lateral position. The meta-analysis confirmed that the variant is uncommon, supported left-sided predominance, and showed that directly observed bilateral occurrence is rare. Separating clavicle-level prevalence, marginal laterality, feasibility-based paired laterality, and body-level bilateral prevalence provided a more appropriate synthesis of incompletely paired evidence.