Different Load-Induced Alterations in Intervertebral Discs Between Low Back Pain Patients and Controls

Abstract

Study Design. Prospective cohort study. Objective. Investigate load-induced effects in lumbar intervertebral discs (IVDs) and differences between low back pain (LBP) patients and controls. Summary of Background Data. T2-map values, obtained from quantitative MRI sequences, reflect IVD tissue composition and integrity. Feasibility studies with T2-mapping indicate different load-induced effects in entire IVDs and posterior IVD parts between LBP patients and controls. Larger studies are required to confirm these findings and increase the understanding of specific characteristics distinguishing IVD changes in LBP patients compared with controls. Materials and Methods. Lumbar IVDs of 178 patients (mean age: 43.8 yr; range: 20–60 yr) with >3 months of LBP and 74 controls (mean age: 40.3 yr; range: 20–60 yr) were imaged with T2-map sequence in a 3T scanner in supine position without axial load, immediately followed by a repeated examination, using the same sequence, with axial load. On both examinations, mean T2-map values were obtained from entire IVDs and from central/posterior IVD parts on the three midsagittal slices in 855 patient IVDs and 366 control IVDs. Load-induced effect was compared with Fold-change ratio and adjusted for IVD-degeneration grade. Results. Loading induced an increase in T2-map values in both patients and controls. Excluding most extreme values, the ranges varied between -15% and +35% in patients and -11% and +36% in controls (first to 99th percentile). Compared with controls, the T2-map value increase in patients was 2% smaller in entire IVDs (Fold-change: 0.98, P=0.031), and for central and posterior IVD parts 3% (Fold-change: 0.98, P=0.005), respectively, 2% (Fold-change: 0.9, P=0.015) smaller. Conclusions. This quantitative study confirmed diverse load-induced behaviors between LBP patients and controls, suggesting deviant biomechanical characteristics between IVDs in patients and controls not only attributed to the global grade of degeneration. These findings are an important step in the continuous work of identifying specific IVD phenotypes for LBP patients. Level of Evidence. Level II.