Motion in lumbar functional spine units during side bending and axial rotation moments depending on the degree of degeneration

Study Design. Human lumbar spine specimens were tested in axial rotation an d side bending. Motion was related to the grade of degeneration. Objectives. To determine the degree to which degeneration with fissure form ation in the disc affects axial rotation of the lumbar functional spine uni t. Summary of Background Data. There is controversy in the literature regardin g the influence of severe degeneration and fissures of the disc on the rang e of axial rotation. Methods. Thirty-six lumbar spine specimens were tested in axial rotation an d side bending, by applying pure moments in an unconstrained setting. The m otion in 6 df was recorded by dial gauges. The grade of degeneration was es tablished by the grading schemes of Nachemson,Thompson, Adams, and Mimura. Results. A significant increase of axial rotation and lateral translation u nder torque was found. This increase mainly took place between Grade 3 acco rding to the schemes of Nachemson, Thompson, and Adams (no fissure formatio n) and the higher grades of degeneration(defined by fissure formation). Red uced disc height was always associated with fissures. Conclusions. A reduced lumbar disc height in radiographs seems to be associ ated with fissure formation in the disc. In this case, the range axial rota tion after torque is increased in comparison with cases with less degenerat ion.