Gender variation of human spinal and paraspinal structures.

To investigate the effects of gender on the dimensions of spinal and paraspinal structures, anthropometric assessments were made on 92 patients (39 female and 53 male, aged 20-55 years) suffering low back pain which required computerized tomography for further investigation. During routine scans cross-sectional areas (CSA) of L4 and paraspinal and psoas muscles were measured at the level of the upper table of L4. The results indicated significantly greater cross-sectional areas of all structures in males who were significantly heavier. For both sexes there were significant, linear relationships between L4 and paraspinal and psoas muscle cross-sectional areas and bodyweight. Gender differences were apparent since for each structure regression lines were, although parallel, separated according to sex, with males having significantly greater muscle and bone cross-sectional areas than females. The gender difference between the lines was much greater for psoas than for paraspinal muscles, suggesting the influence of biomechanical, in addition to hormonal, differences between the sexes.