Metacarpal cortical percentage predicts bone density and osteoporotic fracture incidence in inflammatory arthropathy patients: a retrospective cohort study

Summary: Early identification of osteoporosis promotes timely treatment. This retrospective study demonstrated that bone cortical percentage (2MCP) measured on hand X-ray in patients with inflammatory arthritis correlates significantly with bone density, fracture risk and fracture incidence. Routine hand X-ray 2MCP reporting could support identification of patients at risk of osteoporotic fractures. Purpose: Effective osteoporotic screening facilitates earlier identification and treatment of patients at risk. Bone mineral density (BMD) alone has limited sensitivity and may not always be available. This study aimed to show whether radiographic second metacarpal cortical thickness percentage (2MCP) correlates with BMD and fracture incidence. Methods: This retrospective cohort study measured 2MCP in 230 patients with inflammatory arthropathies who underwent both DXA and hand radiograph within 6 months. BMD, FRAX and fracture history was gathered. Results: 2MCP correlated with femoral neck BMD (p < 0.001), T-scores (p < 0.001), FRAX (p < 0.001) and major and all osteoporotic fracture incidence (p < 0.001) across all patient groups. 2MCP ≤ 55% was 88% sensitive and 51% specific in identifying patients with osteoporotic BMD (AUC 0.7893). 2MCP ≤ 65% and ≤ 73% were 100% sensitive for osteoporotic and osteopenic BMD respectively, whilst ≤ 30% and ≤ 39% were 100% specific. 2MCP ≤ 59% demonstrated 92% sensitivity for all low-impact fractures and 2MCP ≤ 56% was 87% sensitive for major osteoporotic fracture (MOF). 2MCP showed superior sensitivity and specificity to osteopenic femoral neck T-score for predicting MOF incidence (AUC 0.7009 and 0.6590). Combining 2MCP with T-score parameters enhanced sensitivity to 94.6% for MOF up to 2 years beyond the hand radiograph. Conclusion: 2MCP presents a fast, inexpensive adjunct to evaluate fracture risk. This technology may enhance BMD sensitivity in predicting MOF and improve global bone health assessment accessibility. 2MCP automation and routine inclusion in hand radiographs could optimise early awareness and diagnosis of patients at risk of osteoporosis and fractures.