Upright MRI after decompression of spinal stenosis and concurrent spondylolisthesis

OBJECTIVEThe treatment of patients with spinal stenosis and concurrent degenerative spondylolisthesis is controversial. Two large randomized controlled clinical trials reported contradictory results. The authors hypothesized that a substantial number of patients will show evidence of micro-instability after a sole decompression procedure.METHODSThis study was a retrospective analysis of all cases of lumbar spinal stenosis treated at the Frankfurt University Clinic (Universitätsklinik Frankfurt) from 2010 through 2013. Patients who had associated spondylolisthesis underwent upright MRI studies in flexion and extension for identification of subtle signs of micro-instability. Clinical outcome was assessed by means of SF-36 bodily pain (BP) and physical functioning (PF) scales.RESULTSA total of 21 patients were recruited to undergo upright MRI studies. The mean duration of follow-up was 65 months (SD 16 months). Of these 21 patients, 10 (47%) showed signs of micro-instability as defined by movement of > 4 mm on flexion/extension MRI. Comparison of mean SF-36 BP and PF scores in the group of patients who showed micro-instability versus those who did not showed no statistically significant difference on either scale.CONCLUSIONSThere seems to be a substantial subset of patients who develop morphological micro-instability after sole decompression procedures but do not experience any clinically significant effect of the instability.