Prevalence, Characteristics, and Clinical Significance of Os Calcaneus Secundarius: A Systematic Review With Meta-Analysis

Introduction The common presence of anatomical variations on the foot and ankle region may be oftentimes associated with painful syndromes. For medical professionals, their resemblance to fractures may pose a diagnostic conundrum, particularly following an incident. Os calcaneus secundarius (OCS), is a rare accessory ossicle located between the anterior process of the calcaneus and the navicular bone. Up to this date, the epidemiology of OCS is not established and poorly understood, as it varies between 0.1% to 15.2%. The aim This study aimed to synthesize the relevant data regarding the prevalence of this accessory ossicle and key clinical aspects, to provide a comprehensive summarization of the existing knowledge, subsequently helping clinicians make a precise diagnosis and plan treatment Materials and methods A thorough search of Pubmed/Medline, Embase, and ScienceDirect was conducted for studies presenting relevant information on OCS. The structure of this study strictly adhered to the PRISMA guidelines and was pre-registered on PROSPERO (ID: CRD42024626488). The random-effect model has been used to calculate the pooled prevalence estimates (PPE). Results In total, 25 articles (25 029 feet), qualified for the inclusion into the quantitative analysis. The PPE of OCS was 1.1% (95%CI: 0.7%-1.6%). There was no significant difference in the prevalence of OCS between sex-based subgroups. The PPE of OCS in studies that used X-ray was 0.7% (95%CI: 0.4%-1.2%) and was substantially lower than in the cadaver-based subgroup, which was 4.4% (95%CI: 2.4%-8.0%; 95%PI: 0.00-0.45). The highest PPE of OCS was noted in Europe – 1.6% (95%CI: 1.1%-2.5%), and the lowest in Asia - 0.5% (95%CI: 0.4%-0.8%). Conclusions In order to minimize orthopedic consultations or even procedures, clinicians should be aware of the significance of the potential encounter of this anatomical variety. Differentiating between an anterior process fracture and the OCS is particularly crucial in the emergency room because of their distinct treatment protocols.