Abstract
PURPOSE: To investigate whether the presence of Modic changes type I (MC I) found on preoperative MRI scans represent a risk factor for persistent back pain 12 months after surgery amongst patients operated for lumbar disc herniation. METHODS: Cohort study of 178 consecutive patients operated with lumbar microdiscectomy. Preoperative MRI scans were evaluated by two independent neuroradiologists. Primary outcome measure was the visual analogue scale (VAS) for back pain. Secondary outcome measures were; VAS for leg pain, physical function (Oswestry disability index), and health-related quality of life (EQ-5D), self-reported benefit of the operation and employment status. The presence of MC I was used as exposition variable and adjusted for other risk factors in multivariate analyses. RESULTS: The Modic classification showed a high inter-observer reproducibility. Patients with MC I had less improvement of back pain 12 months after surgery, compared to those who had no or other types of MC, but this negative association no longer showed statistical significance when adjusted for smoking, which remained the only independent risk factor for persistent back pain. CONCLUSIONS: Patients with preoperative MC I can expect less but still significant improvement of back pain 1 year after microdiscectomy, but not if they smoke cigarettes.