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. 2022 Nov:164:116515.
doi: 10.1016/j.bone.2022.116515. Epub 2022 Aug 7.

Load-to-strength ratio at the radius is higher in adolescent and young adult females with obesity compared to normal-weight controls

Vibha Singhal  1 , Carolyn Huynh  2 , Supritha Nimmala  2 , Deborah M Mitchell  3 , Clarissa C Pedreira  4 , Abeer Bader  5 , Karen Flanders  5 , Jane Zheng  2 , Mary L Bouxsein  6 , Madhusmita Misra  7 , Miriam A Bredella  8
Affiliations

Load-to-strength ratio at the radius is higher in adolescent and young adult females with obesity compared to normal-weight controls

Vibha Singhal et al. Bone. 2022 Nov.

Abstract

Background: Among adolescents with extremity fractures, individuals with obesity have greater representation compared with individuals of normal-weight, despite having higher areal and volumetric bone mineral density (aBMD, vBMD) than their normal-weight counterparts. The relative increase in BMD in individuals with obesity may thus be insufficient to support the greater force generated upon falling. The load-to-strength ratio is a biomechanical approach for assessing the risk of fracture by comparing applied force to bone strength, with higher load-to-strength ratios indicating higher fracture risk.

Objective: To assess the load-to-strength ratio at the distal radius in adolescent and young adult females with severe obesity (OB) compared with normal-weight healthy controls (HC). We hypothesized that OB have a higher load-to-strength ratio compared to HC.

Methods: We examined bone parameters in 65 girls 14-21 years old: 33 OB and 32 HC. We used dual-energy X-ray absorptiometry (DXA) to assess body composition, high resolution peripheral quantitative CT (HR-pQCT) to estimate vBMD, and microfinite element analysis (μFEA) to assess bone strength at the distal radius. To quantify fracture risk, we computed the load-to-strength ratio, where the numerator is defined as the load applied to the outstretched hand during a forward fall and the denominator is the bone strength, as estimated by μFEA.

Results: Although OB had higher total vBMD than HC (368.3 vs. 319.9 mgHA/cm3, p = 0.002), load-to-strength ratio at the radius was greater in OB than HC after controlling for age and race (0.66 vs. 0.54, p < 0.0001). In OB, impact force and load-to-strength ratio were associated negatively with % lean mass (r = -0.49; p = 0.003 and r = -0.65; p < 0.0001 respectively) and positively with visceral fat (r = 0.65; p < 0.0001 and r = 0.36; p = 0.04 respectively).

Conclusions: Adolescent and young adult females with obesity have higher load-to-strength ratio at the distal radius due to higher forces applied to bone in a fall combined with incomplete adaptation of bone to increasing body weight. This is differentially affected by lean mass, fat mass, and visceral fat mass.

Keywords: Adolescents; Fracture; Load-to-strength ratio; Obesity; Radius.

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Conflict of interest statement

Conflicts of Interest: Authors have no conflicts of interest to disclose relevant to this paper.

Figures

Figure 1:
Figure 1:
Load-to-Strength Ratio in Females with Obesity (OB) and Normal-Weight Healthy Controls (HC) at the Radius. (Line indicates mean)
Figure 2:
Figure 2:
Associations of % Lean Mass with Load-to-strength Ratio
See this image and copyright information in PMC

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