Rapid growth produces transient cortical weakness: A risk factor for metaphyseal fractures during puberty

Abstract

Fractures of the distal radius in children have a similar incidence to that found in postmenopausal women but occur more commonly in boys than in girls. Fractures of the distal tibia are uncommon in children and show no sex specificity. About 90% of lengthening of the radius but only 30% of lengthening of the tibia during puberty occur at the distal growth plate. We speculated that more rapid modeling at the distal radial metaphysis results in a greater dissociation between growth and mineral accrual than observed at the distal tibia. We measured the macro-and microarchitecture of the distal radial and tibial metaphysis using high-resolution peripheral quantitative computed tomography in a cross-sectional study of 69 healthy boys and 60 healthy girls aged from 5 to 18 years. Bone diameters were larger but total volumetric bone mineral density (vBMD) was lower at the distal radius (not at the distal tibia) by 20% in boys and by 15% in girls at Tanner stage III than in children of the same sex at Tanner stage I (both p < .05). In boys at Tanner stage III, total vBMD was lower because the larger radial total cross-sectional area (CSA) had a thinner cortex with lower vBMD than in boys at Tanner stage I. In girls at Tanner stage III, the larger total radial CSA was not associated with a difference in cortical thickness or cortical vBMD relative to girls in Tanner stage I. Cortical thickness and density at both sites in both sexes after Tanner stage III were greater than in younger children. Trabecular bone volume fraction (BV/TV) was higher in boys than in girls at both sites and more so after puberty because trabeculae were thicker in more mature boys but not in girls. There was no sex-or age-related differences in trabecular number at either site. We infer that longitudinal growth outpaces mineral accrual in both sexes at the distal radius, where bone grows rapidly. The dissociation produces transitory low cortical thickness and vBMD in boys but not in girls. These structural features in part may account for the site and sex specificity of metaphyseal fractures during growth. ß

Adolescent Girls With Anorexia Nervosa Have Impaired Cortical and Trabecular Microarchitecture and Lower Estimated Bone Strength at the Distal Radius

“…The distribution of cortical pores in AN, specifically whether increases in porosity predominately occur along the endosteum, warrants further investigation. The incidence of fractures at the radius peaks during the peripubertal years in girls and boys (20,21) and has been attributed to a transient dissociation between peak statural bone growth and peak bone mineral accumulation, which results in elevated cortical porosity (27,32). This dissociation may be further exacerbated in AN, leading to the observed findings.…”

Quantitative Computed Tomography and Computed Tomography in Children

“…Wang et al [32] observed similar patterns at the distal radius (4% site) and tibia (7% site). Although crosssectional, these data suggest that the transient weakness in cortical vBMD at the distal radius in mid-puberty was not evident in the tibia.…”

A Critical Comparison Between Two Scanning Protocols of High-Resolution Peripheral Quantitative Computed Tomography at the Distal Radius in Adolescents

“…Accurate measurement of the length of the radius can be difficult; hence, the ulnar length (at the nondominant side) from the tip of the styloid process distally to the tip of the olecranon process with elbow flexed at 90°was measured instead (13). The percentage of coefficient of variation for ulnar length measurement was 1.04%.…”

“…Currently, there is no consensus on the scanning protocol for young subjects with open growth plates, which are radiation-sensitive regions and should be avoided during scanning (7). In general, there exist 2 types of scanning protocols, namely, those with ROI starting at a fixed distance (1, 2, 5, or 9.5 mm) or a relative offset (4% or 7%) of the ulnar length proximal to different reference lines (7)(8)(9)(10)(11)(12)(13). Due to the diversity of existing protocols, it is difficult to perform cross-study comparisons and to merge datasets from different centers for analysis.…”