10-year Longitudinal MRI Study of Intervertebral Disk Degeneration in Patients With Lumbar Spinal Canal Stenosis After Posterior Lumbar Decompression Surgery

Study Design. A prospective longitudinal magnetic resonance imaging (MRI) study. Objective. The objective of this study was to describe the progression of intervertebral disk (IVD) degeneration in patients who underwent posterior decompression surgery for lumbar spinal canal stenosis (LSS). Summary of Background Data. IVD degeneration contributes to the pathogenesis of LSS; however, the long-term consequences of degenerative changes after decompression surgery remain unknown. Materials and Methods. Of 258 consecutive patients who underwent posterior lumbar decompression surgery for LSS, 62 who underwent MRI at their 10-year follow-up were included; 17 age-matched asymptomatic volunteers were analyzed as controls. Three MRI findings representing IVD degeneration were graded on their severity: decrease in signal intensity, posterior disk protrusion (PDP), and disk space narrowing (DSN). Clinical outcome was assessed using the low back pain (LBP) score from the Japanese Orthopaedic Association scoring system. We examined the association between the progression of degenerative changes on MRI and LBP/associated factors using logistic regression adjusting for age at baseline and sex. Results. The severity of IVD degeneration tended to be higher in patients with LSS than asymptomatic volunteers at both baseline and follow-up. IVD degeneration progressed in all patients during the 10-year follow-up period. Progression of decrease in signal intensity and PDP was observed at L1/2 in 73% and at L2/3 in 34%, respectively (the highest frequencies in the lumbar spine). Progression of DSN was highest at L4/5 in 42%. The rates of PDP and DSN progression during the 10-year follow-up period tended to be greater in patients with LSS than in asymptomatic volunteers. No significant difference in the proportion of LBP deterioration was evident for individuals with and without MRI findings of progression. Conclusions. Our study reveals a natural history of the long-term postoperative course of IVD degeneration after posterior decompression surgery for LSS. Compared with healthy controls, patients with LSS seemed to be predisposed to IVD degeneration. Lumbar decompression surgery may promote the progression of DSN; however, progression of IVD degeneration after lumbar decompression surgery was not associated with worsening LBP scores.