The geometry of the muscles of the lumbar spine determined by magnetic resonance imaging.

Magnetic Resonance Imaging (MRI) is a new multiplanar imaging technique that clearly demonstrates soft tissue anatomy. The lumbar spines of 26 males have been scanned. From the transverse scans, the position and cross-sectional areas of the muscles of the lumbar region were recorded. Regression analysis was performed to relate these values to trunk measurements and body weight. Sagittal scans were used to measure the angles to the vertical of the lumbar discs and of the skin overlying the spinous processes. The position of each lumbar disc relative to two skin points was measured. These parameters can then be used in biochemical calculations of low-back forces.