Bone strength and structural deficits in children and adolescents with a distal forearm fracture resulting from mild trauma

Although distal forearm fractures (DFFs) are common during childhood and adolescence, it is unclear whether they reflect underlying skeletal deficits or are simply a consequence of the usual physical activities, and associated trauma, during growth. Therefore, we examined whether a recent DFF, resulting from mild or moderate trauma, is related to deficits in bone strength and cortical and trabecular bone macro- and microstructure compared with nonfracture controls. High-resolution peripheral quantitative computed tomography was used to assess micro-finite element-derived bone strength (ie, failure load) and to measure cortical and trabecular bone parameters at the distal radius and tibia in 115 boys and girls with a recent (<1 year) DFF and 108 nonfracture controls aged 8 to 15 years. Trauma levels (mild versus moderate) were assigned based on a validated classification scheme. Compared with sex-matched controls, boys and girls with a mild-trauma DFF (eg, fall from standing height) showed significant deficits at the distal radius in failure load (-13% and -11%, respectively; p < 0.05) and had higher ("worse") fall load-to-strength ratios (both +10%; p < 0.05 for boys and p = 0.06 for girls). In addition, boys and girls with a mild-trauma DFF had significant reductions in cortical area (-26% and -23%, respectively; p < 0.01) and cortical thickness (-14% and -13%, respectively; p < 0.01) compared with controls. The skeletal deficits in the mild-trauma DFF patients were generalized, as similar changes were present at the distal tibia. By contrast, both boys and girls with a moderate-trauma DFF (eg, fall from a bicycle) had virtually identical values for all of the measured bone parameters compared with controls. In conclusion, DFFs during growth have two distinct etiologies: those owing to underlying skeletal deficits leading to fractures with mild trauma versus those owing to more significant trauma in the setting of normal bone strength.