Epidemiology and Clinical Characteristics of Os Intermetatarseum: A Systematic Review and Meta-analysis

Os intermetatarseum (OI) is an accessory ossicle situated between the first and second metatarsals. While often asymptomatic, its presence can occasionally lead to development of painful syndrome that require a clinical intervention or even surgical excision. However, the data on its prevalence and clinical relevance is limited. Aim of this study is to determine the prevalence of OI and systematically synthesize available data on its clinical characteristics.

Three major databases (PubMed/MEDLINE, Embase, and ScienceDirect) were searched for original studies reporting on OI until July 2025. The study was pre-registered on PROSPERO (ID: CRD420251132172) and strictly followed PRISMA guidelines. Heterogeneity was assessed via the 95% prediction intervals, I² statistic, and χ² test.

A total of 21 studies encompassing 22 157 feet met the inclusion criteria for quantitative analysis. The pooled prevalence estimate (PPE; per foot) of OI in the general population was 1.16% (95% CI 0.75%-1.80%) in the general population. The PPE was comparable between males (0.79%, 95% CI 0.21%-2.90%) and females (0.41%, 95% CI 0.07%-2.35%). Regionally, North America demonstrated a significantly higher PPE (3.11%, 95% CI 2.28%-4.23%) than Asia (0.39%, 95% CI 0.13%-1.21%) but not Europe (1.84%, 95% CI 0.96%-3.51%). No significant difference was found between cadaveric studies (2.68%, 95% CI 1.04%-6.77%) and radiographic studies (0.90%, 95% CI 0.53%-1.52%).

OI is a relatively rare anatomical finding that is present in approximately 1 in 100 feet. High heterogeneity and significant publication bias mean the pooled values are approximate. Nevertheless, its awareness and proper identification are essential, as it may occasionally present with symptoms and mimic other pathologies such as fractures, which require different management strategies.