More Broken Bones: A 4-Year Double Cohort Study of Young Girls With and Without Distal Forearm Fractures

Abstract

Predictors of childhood fractures have not been investigated previously. This study was undertaken to determine whether a previous history of forearm fracture, low bone mineral density (BMD; both areal bone mineral density [aBMD, g/cm2] and volumetric bone mineral apparent density [BMAD, g/cm3]), or anthropometry, influence fracture risk in young girls. At baseline, two cohorts of girls, aged 3–15 years, were evaluated: 100 had recently broken a forearm (group 1) and 100 were fracture free (group 2). Four years later we restudied 170 of these girls (82 from group l and 88 from group 2). We now report the relationships of previous fracture history, baseline BMD (measured by dual-energy X-ray absorptiometry), baseline weight, and height to risk of new fracture. More new fractures occurred in group l (37 fractures in 24 girls) than in group 2 (8 fractures in 7 girls; p = 0.0007). The independent predictors for occurrence of a new fracture at any skeletal site in a multivariate model adjusting for age, weight, total body aBMD, and fracture history were previous fracture (hazard ratio [HR], 3.28; 95% CI, 1.41-7.64); age (HR per l-year increase, 0.91; 95% CI, 0.84-0.99); total body aBMD (HR per l SD decrease, 1.92; 95% CI, 1.31-2.81); and body weight (HR per l SD increase, 1.49; 95% CI, 1.06-2.08). Girls with two risk factors together had substantially greater fracture risk: previous fracture and low spinal BMAD (HR, 9.4; 95% CI, 2.8-32.0), previous fracture and high body weight (HR, 10.2; 95% CI, 2.8-37.6), or previous fracture and low total body aBMD (HR, 13.0; 95% CI, 3.9-43.1). We conclude that previous forearm fracture, low total body aBMD, low spinal BMAD, and high body weight each increase risk of new fractures within 4 years in young girls. Interventions to reduce the risk of fractures, particularly forearm fractures, in girls warrant further study.