腰椎旋转角度对骨密度测量值影响的定量研究

目的定量分析腰椎旋转角度对双能X线法(Dual-energy X-ray absorptiometry,DXA)测量腰椎骨密度值(Bone mineral density,BMD)的影响,并提出校正方法。方法模拟腰椎BMD标准测量方法,将5具成年男性腰椎标本放于特制的可旋转模具上。以5°为增加量,将标本从0°(标准前后位)逐渐旋转至45°,测量不同旋转角度状态下的腰椎BMD。同时,对标本进行X线摄片,根据Nash-Moe法评估椎体的旋转程度,并与DXA获得的图像进行比较。结果随着腰椎旋转角度增加,腰椎的投射面积逐渐增加,骨矿含量无显著性变化,骨密度值逐渐降低。相关性分析表明,腰椎旋转角度与投射面积呈正性相关,与BMD呈负性相关。当旋转度数至15°时,测量BMD值与0°值之间有显著性差异(P=0.001)。当旋转至45°时,BMD降低达21%。根据Nash-Moe法判断腰椎旋转程度,DXA法与X线法的符合率为90%。结论椎体旋转角度对腰椎骨密度值具有显著性影响,可以导致测量值较真实值偏低。对于存在腰椎旋转畸形患者,应当根据旋转角度校正骨密度,以避免过高估计患者骨质疏松严重程度。

A quantative study of the effect of lumbar vertebral rotatIon on bone mineral density

Objective To evaluate the effect of lumbar vertebral rotation on bone mineral density(BMD) measured using dual-energy X-ray absorptiometry(DXA) quantitatively,and to propose a correction method.Methods Five adult male lumbar spine samples were harvested and set on a customized rotational platform.According to the standard lumbar BMD measuring procedures,all specimen were underwent DXA scan in different rotation conditions(from 0 to 45 degrees) and the lumbar BMD data were collected.In addition,X-ray photographs were taken to evaluate the vertebral rotation and to compare with DXA images with respect to the Nash-Moe method.Results With the increment of vertebral rotation,the projection areas increased and BMD decreased.However,the BMD of lumbar spine did not change significantly.The degree of vertebral rotation showed a positive correlation with the projection area and a negative correlation with the BMD.When rotation degree reached to 15 degrees,the lumbar BMD decreased significantly comparing to that in 0 degree.When the rotation degree reached to 45 degrees,the lumbar BMD further decreased by 21%.According to Nash-Moe method,the consistency in evaluation of vertebral rotation was 90% between X-ray and DXA images.Conclusion Lumbar vertebrae rotation has a significant effect on BMD and can lead to lower BMD than true value.For osteoporotic patients combined with rotational lumbar deformities,the measured BMD should be corrected to avoid overestimation of the osteoporosis situation.