Elsevier

Bone

Volume 93, December 2016, Pages 71-78
Bone

Full Length Article
Long bone robustness during growth: A cross-sectional pQCT examination of children and young adults aged 5–29 years

https://doi.org/10.1016/j.bone.2016.09.015Get rights and content

Highlights

  • Ontogeny of skeletal robustness was explored in a cross-sectional dataset.

  • Sexual dimorphism emerged during and after puberty.

  • Reduced robustness observed in age-groups close to adolescent growth spurt

  • Relative slenderness may be related to incidence of frank and stress fractures.

Abstract

Skeletal robustness (cross-section size relative to length) is associated with stress fractures in adults, and appears to explain the high incidence of distal radius fractures in adolescents. However, little is known about the ontogeny of long bone robustness during the first three decades of life. Therefore, we explored the ontogeny of tibial, fibular, ulnar and radial robustness in a cross-sectional sample of 5 to 29 year-old volunteers of both sexes. Peripheral quantitative computed tomography (pQCT) was used to evaluate cross-sections of the leg (4%, 14%, 38% and 66%), and forearm (4%, and 66%) in N = 432 individuals. Robustness was evaluated as the total bone area divided by bone length. Differences between age-groups, sexes, and age-group × sex interactions were evaluated with ANOVA with Tukey's post hocs where appropriate. Most bone sites exhibited more robust bones in men than women (P < 0.001 to 0.02), and in older age-groups than younger (P < 0.001). Sex × age-group interaction was observed at the 66% and 38% tibia sites with robustness increasing more with age in men than in women (P = 0.006 to 0.042). Post-hoc analyses indicated no sex differences prior to 13 years-of-age, and notable exceptions to increasing robustness with age at the 4% radial and 66% tibial sites, which exhibited reduced robustness in age groups close to peak height velocity. In conclusion, the present results suggest that very little sexual dimorphism in long bone robustness exists prior to puberty, and that divergence occurs primarily after cessation of longitudinal growth. A period of relative diaphyseal slenderness was identified at age-groups coinciding with the adolescent growth spurt, which may be related to the relatively high incidence of frank and stress fracture in adolescents.

Introduction

Robustness of long bones is defined as the size of the cross-section relative to length, calculated as total cross-sectional area divided by bone length [1]. Skeletal robustness has long been recognised as a factor associated with stress fracture susceptibility in infantry recruits [2], [3]. Women have a more slender skeletal phenotype than men [4], [5], [6], [7], [8], and a simultaneously higher stress fracture incidence than men [9], [10], [11]. However, little is known about the ontogeny of skeletal robustness in males and females.

As skeletal ontogeny itself has been studied at length, it is well-known that sex differences in the adult skeleton emerge over the pubertal period [8], [12], [13], [14]. It is also well-established that only limited skeletal sexual dimorphism can be detected prior to puberty (e.g. differences in bone width) [8], [15]. Girls reach puberty and the associated growth spurt at an earlier age than boys, and accordingly age at peak height velocity occurs between 11 and 12 years-of-age in girls and 13 and 14 years-of-age in boys [12], [16]. Bone strengthens in a non-uniform fashion during growth transitions as a result of changes in geometric scale [17]. For instance, longitudinal growth precedes cortical thickening, which occasions transient weakening during the adolescent growth spurt. The timing of such relative weakening has been observed to coincide with an increased incidence of distal radius fractures [17], [18]. While the ontogeny of distal radius and tibia [17], [18], and metacarpal diaphyseal [19], [20], [21] robustness have been explored, little examination of the ontogeny of the robustness of the tibial and radial diaphysis has occurred. No work regarding ontogeny of ulnar or fibular robustness is to be found in the literature at all. Considering that the tibial diaphysis is the most common site of stress fractures, and the fibula is also commonly affected [22], the ontogeny of the robustness of the diaphyses of the long bones of the leg warrants exploration.

Therefore, the purpose of the present study was to describe the ontogeny of tibial, fibular, radial and ulnar robustness in a cross-sectional sample of 5 to 29 year-old volunteers of both sexes. It was hypothesized that 1) differences in robustness between sexes would be more marked in the older participants than younger, and 2) robustness would be lower at age-groups corresponding to the age at peak height velocity.

Section snippets

Materials and methods

The present study is a reanalysis of previously published data [23], [24], [25], [26], [27], [28] collected at Griffith University, Gold Coast, Australia. Participants were included if they were fully ambulatory and in good general health. Exclusion criteria included medications known to affect bone, medical conditions that restrict physical activity participation, and recent lower limb fracture or other immobilized injury. Strategies used to recruit the participants included contacting local

Results

In total, data from N = 247 boys/men, and N = 185 girls/women was identified from our database. As not all participants had undergone forearm examination, the numbers of participants with forearm data were N = 136, and N = 119 for boys/men and girls/women, respectively (Table 2, Supplementary data). No sex differences were observed in age for any of the age-groups, nor were any sex differences present in height, weight, leg or forearm MuA or Fat% in groups younger than 13 years-of-age. Height, weight,

Discussion

The aim of this work was to describe the ontogeny of tibial, fibular, ulnar and radial robustness in males and females from early childhood into the third decade of life. We hypothesized, and observed that sex differences in skeletal robustness (the size of the cross-section relative to length) become more marked with age. In fact, no sex differences in robustness were detected at all in the age-categories prior to nine years of age. Furthermore, we identified a relative reduction in robustness

Disclosure summary

No conflicts of interest.

Acknowledgements

Dr. Rantalainen was supported by an Alfred Deakin Postdoctoral Research Fellowship during the preparation of this manuscript. The R project (http://www.R-project.org/) was used to plot the figures.

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  • Cited by (0)

    Grants or fellowships supporting the writing of the paper: Dr Rantalainen was supported by an Alfred Deakin Postdoctoral Research Fellowship during the preparation of this manuscript.

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