Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, United States of America; Division of Pediatric Endocrinology, Massachusetts General for Children, Harvard Medical School, United States of America; Massachusetts General Hospital Weight Center, United States of America.
Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, United States of America.
Bone. 2022 Nov;164:116515. doi: 10.1016/j.bone.2022.116515. Epub 2022 Aug 7.
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.
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.
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.
Although OB had higher total vBMD than HC (368.3 vs. 319.9 mgHA/cm, 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).
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.
在四肢骨折的青少年中，肥胖个体的比例高于体重正常的个体，尽管肥胖个体的面积和体积骨矿物质密度（aBMD、vBMD）高于体重正常的个体。因此，肥胖个体的骨密度相对增加可能不足以支撑跌倒时产生的更大力量。负荷-强度比是一种通过比较施加力与骨强度来评估骨折风险的生物力学方法，较高的负荷-强度比表示骨折风险较高。
评估严重肥胖（OB）的青少年和年轻成年女性与体重正常的健康对照组（HC）相比，桡骨远端的负荷-强度比。我们假设 OB 的负荷-强度比高于 HC。
我们检查了 65 名 14-21 岁女孩的骨骼参数：33 名 OB 和 32 名 HC。我们使用双能 X 射线吸收法（DXA）评估身体成分，高分辨率外周定量 CT（HR-pQCT）评估 vBMD，微有限元分析（μFEA）评估桡骨远端的骨强度。为了量化骨折风险，我们计算了负荷-强度比，分子定义为向前跌倒时施加到手的力，分母是通过 μFEA 估计的骨强度。
尽管 OB 的总 vBMD 高于 HC（368.3 对 319.9 mgHA/cm，p=0.002），但在控制年龄和种族后，OB 的桡骨远端的负荷-强度比高于 HC（0.66 对 0.54，p<0.0001）。在 OB 中，冲击力和负荷-强度比与瘦体重百分比呈负相关（r=-0.49；p=0.003 和 r=-0.65；p<0.0001），与内脏脂肪呈正相关（r=0.65；p<0.0001 和 r=0.36；p=0.04）。
由于跌倒时施加到骨骼的力较高，以及骨骼对体重增加的不完全适应，肥胖的青少年和年轻成年女性桡骨远端的负荷-强度比较高。这受到瘦体重、脂肪量和内脏脂肪量的不同影响。
