Measurement of muscle cross-sectional area of the trunk and the lower extremities in subjects with history of low back pain

IT IS A COMMONLY ACCEPTED conclusion that patients with low back pain (LBP) have weaker trunk muscles than the normal population, However, insufficient attention has been paid to muscles of lower extremities in LBP subjects, This study measured trunk and thigh muscles and analyzed the cause of weak trunk muscles in LBP subjects, The 75 volunteers were divided into four groups: male and female control, and male and female LBP group. Cross-sectional areas of trunk and thigh muscles were measured by planimeter on MRI transverse images of L3-4 and mid-thigh levels, Strong correlation between trunk and thigh muscle areas was noted in all groups (r = 0.75 in the male control, r = 0.54 in the male group, r = 0.88 in the female control, and r = 0.71 in the female LBP group). The results of the study revealed linear correlation between the trunk and the thigh muscle areas, This suggests that the LBP subjects who have small trunk muscles also have smart thigh muscles. Thus the weakness of the trunk muscles of some LBP patients may be caused not by the atrophy of localized muscles, but by generalized muscular wasting and/or poorly developed musculature.