Development and Validation of a Nigeria-Specific Fragility Fracture Risk Assessment Tool for Postmenopausal Women: A Mixed-Methods Multicentre Study

Fragility fracture prediction tools such as FRAX have been validated primarily in European and North American populations and may have limited applicability in African cohorts due to differences in bone geometry, lifestyle factors, and population-level osteoporosis epidemiology. This study develops and validates a Nigeria-specific fragility fracture risk assessment tool for postmenopausal women, integrating qualitative contextual inquiry with quantitative clinical measurement. Phase one involves a systematic review of existing risk factors in Nigerian cohort studies and formative qualitative work with 60 postmenopausal women and 30 clinicians across six states representing all geopolitical zones. Phase two involves a prospective cohort study recruiting 800 postmenopausal women across eight sites in Lagos, Kano, Enugu, Port Harcourt, Sokoto, Maiduguri, Abuja, and Abeokuta, followed for three years for incident fragility fracture. Bone mineral density, body composition, dietary calcium, physical activity, ethnicity-specific morphometric indices, hormonal status, and previous fracture history will be captured. The Nigeria Fragility Risk Score (NFRS) will be derived using multivariable Cox proportional hazards modelling, and its discrimination and calibration validated internally and against FRAX. The study hypothesises that the NFRS demonstrates superior predictive accuracy for Nigerian women compared to FRAX. Findings will be submitted to the World Health Organisation and the Nigerian Osteoporosis Society for endorsement and clinical integration. Keywords: fragility fractures, risk assessment, osteoporosis, Nigerian women, tool development.