MRI-based morphological parameters to quantify lumbar disc degeneration

Abstract

When an intervertebral disc degenerates, structural deterioration occurs in a wide range of anatomical components within and adjacent to the disc, being clearly represented in cross-sectional imaging. To suggest reliable and valid MRI-based morphologic parameters to quantify lumbar disc degeneration, the reliabilities of 6 parameters were analyzed to choose those with high reliability. The selected parameters were further tested to determine validity by correlating with disc height, which is regarded as a hallmark of structural integrity of the intervertebral disc. Eighty-five patients over 60 years old who underwent MRI of the lumbar spine for mild low back pain were included. Two reviewers independently assessed the degree of degeneration and assigned one of the 4 ordinal scores from 0 to 3 in the following 6 parameters at 6 spinal segments: T2-signal intensity (T2-SI), disc extension beyond interspace (DEBIT), annular fissure, Modic changes, endplate integrity, and osteophytes. Inter-observer and intra-observer agreements were assessed using Cohen's kappa statistic. For those parameters with high reliability, relationships with disc height were examined by calculating Pearson's correlation coefficients. While intra-observer agreements were excellent for all parameters (weighted kappa range 0.801–0.875), the inter-observer agreements were substantial to excellent for T2-SI, DEBIT, Modic changes, and endplate integrity (weighted kappa range 0.629–0.874), moderate for osteophytes (weighted kappa 0.573), and only fair for annular fissure (weighted kappa 0.29). Modic changes ( r = −0.497, P < 0.01), endplate integrity ( r = −0.359, P = 0.01), and osteophytes ( r = −0.448, P < 0.01) showed strong relationships with disc height whereas T2-SI ( r = −0.149, P = 0.175) and DEBIT ( r = −0.208, P = 0.057) did insignificant correlations. To quantify lumbar disc degeneration using MRI, Modic changes, endplate integrity, osteophytes, T2-SI, and DEBIT could be used as reliable parameters. However, different weights might be applied to each parameter because validities to represent degeneration varied.