Document resource
Objective This study aimed to investigate the prevalence of brachydactyly type A3 (BDA3) and its associated epiphysial development abnormalities in Chinese children aged 3–17 years, and to explore differences based on gender, region and urban–rural demographics.Design Cross-sectional study.Setting The study was conducted across 14 provinces (28 survey sites) in China, as part of a nationwide investigation on skeletal maturation. The population was selected using multistage stratified randomised cluster sampling.Participants A total of 17 850 children (8856 boys and 8994 girls) aged 3–17 years participated. The cohort was drawn from a large-scale survey conducted between 2019 and 2021. Selection criteria included children with no visible clinodactyly or hand function impairments.Methods Non-dominant hand-wrist radiographs were obtained using a portable X-ray device. A retrospective analysis of these radiographs was performed to identify BDA3 and epiphysial development abnormalities. Prevalence rates were calculated and compared across gender, regional and urban–rural groups.Results The overall prevalence of BDA3 was 10.0%, with a higher prevalence in girls (12.9% vs 7.1%; p<0.001). The northern region exhibited a higher prevalence compared with the southern region (11.5% vs 8.6%; p<0.001). No significant differences were observed between urban and rural areas (10.3% vs 9.8%; p=0.32). Among the BDA3 phenotypes, brachymesophalangia-5 with cone-epiphysis of mid-5 (BMP5) and BMP5 alone had prevalences of 3.6% and 6.4%, respectively. Both phenotypes were more common in girls compared with boys (p<0.001 for both).Conclusions This nationwide, multicentre study provides the first national epidemiologic data on BDA3 and associated epiphysial features in Chinese children and adolescents, establishing a prevalence of 10.0%. This baseline supports counselling that a straight, well-functioning short fifth finger is a common anatomic variant and may help reduce unnecessary concern.