Modlesky Christopher M, Slade Jill M, Bickel C Scott, Meyer Ronald A, Dudley G A
Department of Health, Nutrition and Exercise Sciences, University of Delaware, Newark, DE 19716, USA.
Bone. 2005 Feb;36(2):331-9. doi: 10.1016/j.bone.2004.10.012.
Spinal cord injury (SCI) results in a dramatic loss of bone mineral and a marked increase in fracture incidence in the femur; however, its effect on the femur's geometric structure and strength is poorly studied. The primary purpose of the present study was to assess the geometric structure, composition, and strength of the midfemur in men with long-term (>2 years), complete SCI (C6-L1 level; n=7) relative to men without SCI (n=8). T1-weighted axial images of the thigh were collected on a GE 1.5-T magnetic resonance imager and geometric, structure, composition, and strength measurements of the midfemur and skeletal muscle volume of the midthigh were determined. Areal bone mineral density (aBMD), bone mineral content (BMC), and bone area of the midthird of the femur and arms were determined using dual-energy X-ray absorptiometry. There were no differences in age, height, weight, femur length, arm BMC, arm aBMD, or arm bone area between the SCI group and controls. While the volume of the midfemur was not different in the two groups, the medullary cavity had 53% more volume and was 21-25% wider in the SCI group (P<0.05). In contrast, the cortical wall in the SCI group had a 24% lower volume and was 27-47% thinner (P<0.05). The cortical wall was particularly thin in the posterior section of the bone. The SCI group also had lower BMC and aBMD in the midfemur (21% and 25%, respectively, P<0.05). Calculated cross-sectional moment of inertia (CSMI), section modulus (Z), and polar moment of inertia (J) were lower in the SCI group (13-19%, P<0.05). A higher ratio of cortical bone volume to muscle volume and BMC to muscle volume in the SCI group (P<0.05) suggests that there was a greater loss of muscle than cortical bone after SCI; however, muscle volume was strongly correlated with cortical bone volume and BMC in the SCI and control groups (r=0.71 to 0.90, P<0.05). Muscle volume was also moderately to strongly correlated with CSMI and Z in the anterior-posterior direction and J. Muscle volume was weakly correlated or not correlated with bone strength measures in the control group (P>0.05). These findings suggest that after SCI, the midfemur erodes on the endosteal surface, resulting in a decreased resistance to bending and torsion. Although midthigh muscle volume appears to decline to a greater degree than midfemur cortical bone volume and BMC, their relationships remain strong.
脊髓损伤（SCI）会导致骨矿物质显著流失，股骨骨折发生率显著增加；然而，其对股骨几何结构和强度的影响却鲜有研究。本研究的主要目的是评估长期（>2年）完全性SCI（C6 - L1水平；n = 7）男性与无SCI男性（n = 8）的股骨中段的几何结构、成分和强度。在GE 1.5 - T磁共振成像仪上采集大腿的T1加权轴向图像，并测定股骨中段和大腿中部骨骼肌体积的几何、结构、成分和强度。使用双能X线吸收法测定股骨和手臂中三分之一处的骨面积骨密度（aBMD）、骨矿物质含量（BMC）和骨面积。SCI组与对照组在年龄、身高、体重、股骨长度、手臂BMC、手臂aBMD或手臂骨面积方面无差异。虽然两组的股骨中段体积无差异，但SCI组的髓腔体积多53%，宽度大21 - 25%（P < 0.05）。相比之下，SCI组的皮质骨壁体积低24%，薄27 - 47%（P < 0.05）。骨的后部皮质骨壁尤其薄。SCI组股骨中段的BMC和aBMD也较低（分别低21%和25%，P < 0.05）。SCI组计算得出的截面惯性矩（CSMI）、截面模量（Z）和极惯性矩（J）较低（13 - 19%，P < 0.05）。SCI组皮质骨体积与肌肉体积以及BMC与肌肉体积的比值较高（P < 0.05），这表明SCI后肌肉的损失比皮质骨更大；然而，SCI组和对照组中肌肉体积与皮质骨体积和BMC密切相关（r = 0.71至0.90，P < 0.05）。肌肉体积在前后方向上与CSMI和Z以及J也呈中度至高度相关。在对照组中，肌肉体积与骨强度指标弱相关或不相关（P > 0.05）。这些发现表明，SCI后股骨中段在内膜表面受到侵蚀，导致抗弯和抗扭能力下降。尽管大腿中部肌肉体积的下降程度似乎比股骨中段皮质骨体积和BMC更大，但它们之间的关系仍然密切。
