Incidence and Severity of Epidural Fibrosis after Back Surgery: An Endoscopic Study

Background: Epidural fibrosis has been implicated in the etiology of persistent pain after back surgery (Failed Back Surgery Syndrome [FBSS]). Using spinal endoscopy to view the lumbosacral epidural cavity, the incidence, severity, and appearance of epidural fibrosis was evaluated in patients with FBSS. Methods: A prospective cohort observational study using epidural endoscopy was done involving 78 patients with persistent pain after back surgery. Patients were evaluated prospectively for the presence of epidural fibrosis and fibrosis was rated using a 4-level grading system based on appearance and resistance to epiduroscope advancement. The incidence of fibrosis detected by epiduroscopy vs. the incidence as reported in magnetic resonance imaging (MRI) studies for the same patients were compared. Results: As diagnosed with epiduroscopy, 83.3% of all patients with persistent pain after back surgery had severe (grade 3 or 4) epidural fibrosis, while 91.0% had significant (grade 2, 3, or 4) fibrosis. In patients who had undergone more extensive surgery, severe fibrosis was present in 91.1% and significant fibrosis in 95.6%. Using MRI, epidural fibrosis was diagnosed only in 16.1% of these patients. All patients with severe epidural fibrosis had a filling defect on epidurography. Concordant pain was present in 84.3% of patients and depended on the severity of fibrosis. Results were statistically evaluated using analysis of frequencies and t-test. P < 0.05 was considered statistically significant. Conclusions: Epiduroscopy demonstrates that the prevalence of severe epidural fibrosis after FBSS is substantially higher than is generally reported in MRI evaluations. Severe epidural fibrosis is an underlying pathology in most patients with FBSS.