Title

Microfinite element modeling reveals that transient deficits in cortical bone may underlie the adolescent peak in forearm fractures

Document Type

Article

Department

Paediatrics and Child Health

Abstract

The incidence of distal forearm fractures peaks during the adolescent growth spurt, but the biomechanical basis for this is unclear. Thus, we studied the distal radius of healthy 6-21 yr-old males (n = 61) and females (n = 66) using high-resolution pQCT (XtremeCT, Scanco, voxel size 82 microns). Subjects were classified into 5 groups by bone age (BA): Group I (pre-puberty, BA 6-8 yrs), Group II (early puberty, BA 9-11 yrs), Group III (mid-puberty, BA 12-14 yrs), Group IV (late puberty, BA 15-17 yrs) and Group V (post-puberty, BA 18-21 yrs). Compared to Group I, trabecular parameters (bone volume, density, trabecular number, and trabecular thickness) did not change in girls (P > 0.2), but increased in boys (P < 0.05) from late puberty onwards. Cortical thickness and volumetric BMD decreased from pre- to mid-puberty in girls (P < 0.01) but were unchanged in boys (P > 0.05) before rising to higher levels at the end of puberty (P < 0.001). Total bone strength, assessed using microfinite element (μFE) models, increased linearly across age groups in both sexes, with boys showing greater bone strength than girls after mid-puberty (P < 0.01) (Fig. A, B). Because the proportion of load borne by cortical vs. trabecular bone reflects, in part, the relative strengths of these compartments, we also evaluated how this changed during growth. As shown in Fig. C and D, the proportion of load borne by cortical bone (derived from the μFE models) decreased transiently during puberty in both sexes, mirroring the incidence of distal forearm fractures previously reported in this community (Fig. E, F). Since cadaveric studies (Osteoporosis Int 14:345, 2003) have demonstrated that cortical bone is a critical determinant of failure load at the wrist, the observed transient shift of load-bearing from cortical to trabecular bone in both sexes during puberty, and the concordance of this with the incidence of adolescent fractures, suggest that regional deficits in cortical bone may underlie the adolescent peak in forearm fractures. Further studies comparing adolescents with and without forearm fractures are needed to test whether children with fractures have greater deficits in cortical bone than children without fractures.

Comments

This work was published before the author joined Aga Khan University.

Publication

Journal of Bone and Mineral Research

Share

COinS