Flexion creep deformation and hysteresis in the lumbar vertebral column.

Fresh lumbar vertebral columns from nine male subjects aged from six to 61 years were tested for creep deformation and hysteresis. The standard test applied a load of 3.5 kg for one hour through a weight and pulley circuit. Additional tests used 1 kg and 5.5 kg for varying periods of time. The four oldest columns showed a pronounced decrease in the range of flexion movement but a consistent increase in the flexion creep deformation. Hysteresis recovery on load removal was more prolonged and less complete in the older lumbar columns than in the young.