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

Abstract

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.

Figures

Fig. 1

Spine tester with human lumbar cadaveric specimen L2-S2. The three-dimensional motion between L3/4 and L4/5 was measured with two electrogoniometric linkage systems. At the top is the gimbal arranged with stepper motor for the application of external moments

Fig. 2

The figures show the range of motion (ROM), neutral zone (NZ) and neutral zone ratio (NZR) in the form of a bar char showing the mean values and standard deviation executed by L3/4 on flexion/extension, left/right bending and right/left rotation

Fig. 3

Presentation of the three flexiblity parameters of L4/5 and the relationship between a modified grading system on degenerative disk disease based on 1. radiographs, 1.1 AP/lateral position (Mimura-score), 1.2 oblique position (Pathria-score) and 2. patho-anatomic criteria, 2.1 macrsocopic findings (Nachemson-score), 2.2 microscopic findings (Vernon-Roberts-score)

Fig. 4

Microscopic grading of disk degeneration a: few focal chondrocytic proliferation, isolated flat fissures, clefts, splints; isolated small areas of necrosis. Here (HE, 20×): four normal layers of annulus fibrosus

Fig. 5

Microscopic grading of disk degeneration b: moderate reactive chondrocytes, ample flat fissures, clefts, splints; several focal areas of necrosis and three rings of intact annular layers. Here (HE, 100×): microcysts and ample flat fissures

Fig. 6

Microscopic grading of disk degeneration b: moderate reactive chondrocytes; ample flat fissures, clefts, splints; several focal areas of necrosis and two rings of intact annular layers. Here (HE, 100×): moderate reactive chondrocytes

Fig. 7

Microscopic grading of disk degeneration c: ample chondrocyte proliferation; numerous deep fissures, clefts, splints; multiple, partly confluent areas of necrosis and 1ring of intact annular layers. Here (HE, 80×): multiple focal and diffus partly confluent necrosis

Fig. 8

Macroscopic grading of disk degeneration. Lumbar disk L3/4 left and L4/5 right, Nachemson grade c: loosening of gel-like consistent and radial clefts