Measurements of axial rotation of the thoracolumbar spine during conditions of standing, sitting, lateral bending, and level walking were made in living subjects; Steinmann pins were inserted in various thoracolumbar spinous processes of seven male subjects, between twenty and twenty-six years old, and direct measurements were made of the angular displacement of the pins during rotation.

The subjects (standing erect, then sitting, with rotation measured relative to the fixed pelvis) turned from side to side as far as possible. In one subject, 9 degrees of rotation occurred between the first and the fifth lumbar vertebrae during standing and 8 degrees during sitting; additional rotation of approximately 10 degrees was observed at the thoracolumbar joint. An average of approximately 6 degrees was measured at each of the remaining thoracic levels. Some individual variation in the amount of axial rotation was observed in the subjects tested.

In one half of a walking cycle during normal level walking on a treadmill, 5 degrees of rotation occurred at the first thoracic vertebra and, in the opposite direction, 6 degrees at the fifth lumbar vertebra. There appeared to be a transition point (displacement node) in the sixth to eighth thoracic vertebral region above which rotation was in the direction opposite to that below.

In an additional study, axial rotation was found to occur with motion of the spine in the coronal plane, an observation that supports the concept that axial rotation is an integral motion of the thoracolumbar spine during lateral bending.