LUMBAR DISC DEGENERATION AND SEGMENTAL INSTABILITY - A COMPARISON OF MAGNETIC-RESONANCE IMAGES AND PLAIN RADIOGRAPHS OF PATIENTS WITH LOW-BACK-PAIN

We analyzed disc space height, angular displacement, tilting movement, and horizontal displacement in 109 patients with low back pain and/or sciatica, on plain radiographs of the lumbar spine. These parameters were compared with the grade of disc degeneration as evaluated by magn etic resonance imaging with the aim of studying lumbar segmental insta bility. Disc space height decreased in proportion to the grade of disc degeneration. Angular displacement was significantly less with severe disc degeneration, accompanied by a tendency to stabilization of the motion segment. Tilting movement and horizontal displacement did not c orrelate with the grade of disc degeneration. Lumbar segmental instabi lity was recognized at all levels even in individuals who appeared to be normal or to have mild disc degeneration. The incidence of lumbar s egmental instability at the L3-4 level was significantly higher in pat ients with normal discs or mild disc degeneration. At the L4-5 and L5- S levels it did not differ between different grades of disc degenerati on.