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.