The biomechanical basis of vertebral body fragility in men and women
The biomechanical basis of vertebral body fragility in men and women
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DOI：
10.1359/jbmr.2001.16.12.2276
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发表时间：
2001-12-01
影响因子：
6.2
通讯作者：
Turner, CH
中科院分区：
文献类型：
--
作者：
Duan, YB;Seeman, E;Turner, CH
这项研究的目的是量化老年男性和女性脊柱骨折风险的生物力学基础。当施加的载荷与其强度相似或大于其强度时，骨骼很可能骨折。为了量化这种风险，我们开发了一个基于椎体压缩负荷和强度比率的骨折风险指数(FRI)。负荷由上半身体重、身高和肌力矩臂决定，力量由横截面积(CSA)和体积骨密度(VBMD)估计。当载荷小于骨的强度时，FRI保持<；1。对于任何给定的载荷，一旦由于vBMD失效而导致骨强度降低，FRI将增加。如果Fri接近或超过Unity，则很可能出现椎体结构性故障。采用双能X线骨密度仪(DXA)对327例健康男性、686例健康女性、26例男性、55例绝经后女性椎体骨折患者的椎体CsA、vBMD进行侧位和后位扫描，计算椎体压缩应力(单位面积负荷)。与直立相比，需要上半身前屈的活动对脊椎造成的压应力类似于10倍。男性和女性在青年时期的vBMD峰值相似。由于男性比女性身高更高，施加在椎体上的负荷更高(3754+/-65N比3051+/-31N；p<；0.001)。然而，由于男性的CsA也高于女性，单位CsA的峰值负荷(应激)没有性别差异(317.4+/-4.7N/cm(2)对321.9+/-3.3N/cm(2)，NS)。年轻男性和女性的FRI相似，但远低于统一(0.42+/-0.02比0.43+/-0.01；NS)。在衰老过程中出现性别差异；CSA在男性和女性中都有所增加，但在男性中增加更多，因此单位面积负荷(压力)减少，但男性比女性更明显。VBMD在男女中都有所下降，但男性的下降幅度较小。这些变化体现在FRI中，男性增加了21%，女性增加了102%，因此只有9%的老年男性和26%的老年女性的FRI大于或等于1。脊椎骨折患者的FRI大于或等于1(1.03+/-0.13比1.35+/-0.13；p<；0.05)，分别比年龄匹配的男性和女性高2.04 SD和2.26 SD。总而言之，年轻男性和女性的vBMD、椎体应力和FRI相似。在衰老过程中，男性CsA增加较多，vBMD下降较少。因此，患骨折风险的男性比女性少，因为这些骨骼强度的结构性决定因素低于负荷超过骨骼承受能力的水平的男性比女性少。男性和女性脊椎骨折的FRIS等于或超过了统一。结果表明，椎骨的骨折阈值可以用既定的生物力学原理来定义；这种方法是否比目前的骨密度T评分-2.5SD具有更高的敏感性和特异度尚不清楚。
The aim of this study was to quantify the biomechanical basis for vertebral fracture risk in elderly men and women. A bone is likely to fracture when the loads imposed are similar to or greater than its strength. To quantify this risk, we developed a fracture risk index (FRI) based on the ratio of the vertebral body compressive load and strength. Loads were determined by upper body weight, height, and the muscle moment arm, and strength was estimated from cross-sectional area (CSA) and volumetric bone mineral density (vBMD). With loads less than the strength of the bone, the FRI remains < 1. For any given load, once bone strength diminishes due to a failing vBMD, the FRI will increase. Should FRI approach or exceed unity, structural failure of the vertebra is likely. We measured vertebral body CSA vBMD of the middle zone of third lumbar vertebra by lateral and posteroanterior (PA) scanning using dual-energy X-ray absorptiometry (DXA) and calculated vertebral compressive stress (load per unit area) in 327 healthy men and 686 healthy women and 26 men and 55 postmenopausal women with vertebral fractures. Activities that require forward bending of the upper body caused similar to 10-fold more compressive stress on the vertebra compared with standing upright. Men and women had similar peak vBMD in young adulthood. Because men have greater stature than women, the loads imposed on the vertebral body are higher (3754 +/- 65 N vs. 3051 +/- 31 N; p < 0.001). However, because CSA also was higher in men than women, peak load per unit CSA (stress) did not differ by gender (317.4 +/- 4.7 N/cm(2) vs. 321.9 +/- 3.3 N/cM(2), NS). The FRI was similar in young men and women and well below unity (0.42 +/- 0.02 vs. 0.43 +/- 0.01; NS). Gender differences emerged during aging; CSA increased in both men and women but more so in men, so load per unit area (stress) diminished but more so in men than in women. vBMD decreased in both genders but less so in men. These changes were captured in the FRI, which increased by only 21 % in men and by 102 % in women so that only 9 % of elderly men but 26 % of elderly women had an FRI greater than or equal to 1. Men and women with vertebral fractures had an FRI that was greater than or equal to unity (1.03 +/- 0.13 vs. 1.35 +/- 0.13; p < 0.05) and was 2.04 SD and 2.26 SD higher than age-matched men and women, respectively. In summary and conclusion, young men and women have a similar vBMD, vertebral stress, and FRI. During aging, CSA increases more, and vBMD decreases less in men than in women. Thus, fewer men than women are at risk for fracture because fewer men than women have these structural determinants of bone strength below a level at which the loads exceed the bone's ability to tolerate them. Men and women with vertebral fractures have FRIs that are equal to or exceed unity. The results show that a fracture threshold for vertebrae can be defined using established biomechanical principles; whether this approach has greater sensitivity and specificity than the current BMD T score of -2.5 SD is unknown.