Research Article: Whole-body and segmental analysis of body composition in adult males with achondroplasia using dual X-ray absorptiometry

Date Published: March 19, 2019

Publisher: Public Library of Science

Author(s): David Sims, Gladys Onambélé-Pearson, Adrian Burden, Carl Payton, Christopher Morse, Sakamuri V. Reddy.


Achondroplasia is a condition characterized by a genetic mutation affecting long bone endplate development. Current data suggests that the bone mineral content (BMC) and bone mineral density (BMD) of achondroplasic populations are below age matched individuals of average stature (controls). Due to the disproportionate limb-to-torso length compared to controls however, the lower BMC and BMD may be nullified when appropriately presented. The aim of this study was to measure whole-body and segmental body composition in adult males with achondroplasia (N = 10, 22 ±3 yrs), present data relative to whole-body and whole-limb values and compare all values to age matched controls (N = 17, 22 ±2 yrs). Dual X-ray absorptiometry (DEXA) was used to measure the in vivo mass of the whole-body and 15 segments, from which BMD, BMC, fat free mass (FFM) and body fat mass were measured. BMC of lumbar vertebrae (L1-4) was also measured and presented as a volumetric BMD (BMDVOL). The achondroplasic group had less BMC, BMD and FFM, and more body fat mass than controls as a whole-body measure. The lower achondroplasic BMC and BMD was somewhat nullified when presented relative to whole-body and whole-limb values respectively. There was no difference in lumbar BMDVOL between groups. Whole-body BMD measures presented the achondroplasic group as ‘osteopenic’. When relative to whole-limb measures however, achondroplasic BMD descriptions were normal. Further work is needed to create a body composition database for achondroplasic population’s, or for clinicians to present achondroplasic body composition values relative to the whole-limb.

Partial Text

Achondroplasia is the most common genetic form of dwarfism and is classically characterized by disproportionate limb-to-torso length and shorter stature (< 1.47 m) compared to persons of average stature without a form of dwarfism (hereafter referred to as ‘controls’). Achondroplasia is brought about by a fibroblast mutation resulting in shorter long-bones which presents a ‘disproportionate’ limb-to-torso lengths compared to controls [1–6]. Despite the available data on the condition, little quantitative confirmation of body composition (here defined as bone mineral content (BMC), bone mineral density (BMD), fat mass and fat free mass (FFM)) has been made. Attempts have been made to describe BMC, BMD, FFM and fat mass in achondroplasic populations but only in heterogeneous groups such as: children during maturation [7], male and female achondroplasic populations of differing ages [8–10] and, case reports [11]. The participant inclusion criteria and in vivo body mass evaluation methods used in these studies are therefore not robust enough to allow appropriate comparisons within achondroplasic populations or to commonly used reference data (e.g. controls). After written informed consent, 10 adult males (22 ±3 yrs), medically confirmed as exhibiting Achondroplasia, and 17 age-matched controls (22 ±2 yrs) agreed to partake in this study. All were free from any injury for at least 3 months and self-reported good health (anthropometric descriptions of each group are given in Table 1). Ethical approval was attained from the local committee (Manchester Metropolitan University) and conformed to the latest revision of the Declaration of Helsinki. Each participant attended one testing session at the laboratories of Manchester Metropolitan University where whole-body anthropometric measurements were carried out. The study was a cross-sectional, between subject design which was developed in line with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement. The aims of this study were to assess the whole-body and segment in vivo BMC, BMD, FFM and fat mass of achondroplasic adults, present values relative to respective whole-body and whole-limb values and compare all values to controls. The findings show that adult achondroplasic males have less BMC, BMD and FFM than controls at the whole-body and segmental level, but body fat masses are the same as controls. The differences in segmental body composition are nullified somewhat when relative to whole-body and whole-limb measures. The aim of this study was to measure and compare body composition between achondroplasic adults and controls. The main findings of this study were that whole-body composition of the achondroplasic group classify them ‘at risk’ of a number of health complications, such as osteoporosis. Presenting achondroplasic body composition relative to whole-body and whole-limb values however, nullifies these classifications and may give a better representation of the achondroplasic groups mass distribution when compared to controls. To make valid clinical descriptions of achondroplasic populations, further work is required to either create separate body composition databases, or, for their body composition to be presented as we have done here.   Source:


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