The relationship between disc degeneration, facet joint osteoarthritis, and stability of the degenerative lumbar spine

Degenerative processes in the disc and facet joints affect the stability of the motion segment. The exact relations among disc degeneration, facet joi nt osteoarthritis, and the kinematics of the motion segment are not well de fined in the literature. Magnetic resonance imaging and functional radiogra phy of the lumbar spine were analyzed to examine the relations among segmen tal instability. facet joint osteoarthritis, and disc degeneration in patie nts with degenerative disorders of the lumbar spine. Seventy consecutive pa tients (mean age, 46 years) had both magnetic resonance imaging and flexion and extension radiographs of the lumbar spine. The lumbar instability was classified into abnormal tilting on flexion, rotatory instability in the sa gittal plane, and translatory instability. Translatory instability was subd ivided into anterior. posterior, and anteroposterior translatory instabilit y. Disc degeneration as seen on T2-weighted sagittal images was classified into five grades. Facet joint osteoarthritis as seen on axial T1-weighted i mages was divided into four grades. This study revealed that the kinematics of the lumbar motion segment an affected by disc degeneration and facet jo int osteoarthritis. Abnormal tilting movement on flexion and anteroposterio r translatory instability both had negative associations with facet joint o steoarthritis. However. anterior translatory instability was positively ass ociated with disc degeneration and facet joint osteoarthritis. Rotatory ins tability in the sagittal plane and posterior translatory instability were n ot associated with disc degeneration and facet joint osteoarthritis.