Grading of degenerative disk disease and functional impairment: imaging versus patho-anatomical findings

Degenerative instability affecting the functional spinal unit is discussed as a cause of symptoms. The value of imaging signs for assessing the resulting functional impairment is still unclear. To determine the relationship between slight degrees of degeneration and function, we performed a biomechanical study with 18 multisegmental (L2-S2) human lumbar cadaveric specimens. The multidirectional spinal deformation was measured during the continuous application of pure moments of flexion/extension, bilateral bending and rotation in a spine tester. The three flexibility parameters neutral zone, range of motion and neutral zone ratio were evaluated. Different grading systems were used: (1) antero-posterior and lateral radiographs (degenerative disk disease) (2) oblique radiographs (facet joint degeneration) (3) macroscopic and (4) microscopic evaluation. The most reliable correlation was between the grading of microscopic findings and the flexibility parameters; the imaging evaluation was not as informative.