Grade three disc degeneration is a critical stage for anterior spondylolisthesis in lumbar spine

Little is known about when and how progressive spondylolisthesis occurs. In this report segmental motion related to age and disc degeneration at L4/5 disc was investigated. 637 patients with low back and/or leg pain underwent radiologic and MRI examinations simultaneously. Because 190 patients with conditions which might impede accurate measurement were excluded, 447 patients, comprising 268 men and 179 women, were included; age range, was 10-86 (mean: 53) years. Three radiologic parameters slip in neutral position (mm), sagittal translation (mm), and segmental angulation (degrees) were examined at the L4/5 segment. On T2-weighted MRI, severity of disc degeneration at L4/5 was classified by Pfirrmann's criteria, grade 1-5. Results showed stage of disc degeneration that progressed according to aging with significant differences except for between grades 4 and 5. Amount of anterior slip was small among grades 1 to 3; however, it greatly increased between grades 3 and 4 and between grades 4 and 5, suggesting that grade 3 disc degeneration has a potential risk of future progression of anterior slip. This finding may also suggest that once significant slip occurs, it will progress to the final grade. Furthermore, the grade 3 degeneration group exhibited large amounts of motion in both angulation and translation, suggesting it was the most unstable group. Our results with radiography and MRI indicate that grade 3 disc degeneration is a critical stage for the progression of lumbar spondylolisthesis at L4/5 segment.