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

Singhal, Vibha; Huynh, Carolyn; Nimmala, Supritha; Mitchell, Deborah M.; Pedreira, Clarissa C.; Bader, Abeer; Flanders, Karen; Zheng, Jane; Bouxsein, Mary L.; Misra, Madhusmita; Bredella, Miriam A.

Affiliations

¹Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, United States of America

²Division of Pediatric Endocrinology, Massachusetts General for Children, Harvard Medical School, United States of America

³Massachusetts General Hospital Weight Center, United States of America

⁴Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, United States of America

⁵Department of Radiology, Massachusetts General Hospital, Harvard Medical School, United States of America

Abstract and keywords

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: Fracture; Obesity; Adolescents; Radius; Load-to-strength ratio; BMD; Bone Mineral Denisty; aBMD; Areal Bone Mineral Density; vBMD; Volumetric Bone Mineral Density; BMI; Body Mass Index; DXA; Dual-energy X-ray Absorptiometry; HR-pQCT; High Resolution peripheral Quantitative CT; µFEA; Micro Finite Element Analysis; MRI; Magnetic Resonance Imaging; VAT; Visceral Adipose Tissue; SAT; Subcutaneous Adipose Tissue

Links

DOI: 10.1016/j.bone.2022.116515

PubMed: 35948256

WoS: 000840839500001

History

Received: 2022-05-2

Revised: 2022-08-3

Accepted: 2022-08-5

Online: 2022-08-7

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Cited By (1)

Year	Entry
2023	Singhal V, Kaur S, Haidar LA, Lee H, Bredella MA, Misra M. Differences in bone accrual over one year in young girls with obesity compared to normal weight controls. Bone. July 2023;172:116757.