The Correlation of Epidural Fibrosis with Epiduroscopic and Radiologic Imaging for Chronic Pain after Back Surgery.

Background: Chronic low back pain is observed frequently after lumbar spinal surgery. Epidural fibrosis has been implicated in the etiology of persistent pain after back surgery. The incidence of epidural fibrosis increases as the number and extent of spinal surgery increases. Epidural fibrosis can be detected by conventional radiologic methods [e.g., lumbosacral magnetic resonance imaging (MRI) with gadolinium], but these methods are insufficient to reveal the presence of epidural adhesions. Imaging of the epidural cavity using an epiduroscope is one of the best methods for visualizing the spinal cavity without damaging anatomic structures.

Objectives: To evaluate the correlation between the type and number of surgery and the degree of epidural fibrosis and to compare epidural fibrosis in epiduroscopic and MRI findings in patients with failed back surgery syndrome (FBSS).

Study Design: A prospective trial.

Setting: A university hospital.

Methods: This study included 61 patients with persistent low back pain and/or radicular pain for at least 6 months, despite lumbar surgery and conservative treatment, and who accepted epiduroscopic imaging. All patients were evaluated in a physical examination using a visual analog scale (VAS) per the elapsed time after surgery. The patients were divided into 3 groups according to the number and type of surgeries. Epidural fibrosis was rated using MRI with gadolinium and epiduroscopy.

Results: When the relationship between admission symptoms and epidural fibrosis was evaluated, MRI findings of fibrosis were found to be significantly higher in all patients with both lumbar and radicular pain symptoms at the confidence level of 95% (P = 0.001). The degree of fibrosis detected using epiduroscopy was grade 1 and 2 in almost all patients who presented with low back pain only, only radicular pain, or only distal paresthesia (P = 0.001). In the correlation analysis between the duration of the postoperative period (4.13 ± 2.97 years) and the degree of fibrosis detected using MRI and epiduroscopy, a statistically significant relationship was found at the confidence level of 95% (P < 0.05). As the number and extent of spinal surgeries increased, the incidence of MRI fibrosis increased, which is compatible with the literature (P = 0.001) There was a statistically significant relationship between the degree of fibrosis as detected using MRI and epiduroscopy at the confidence level of 95% (P < 0.05). Differently, we observed that 6 patients had grade 1 fibrosis as diagnosed using epiduroscopy, whereas none had fibrosis on MRI.

Limitations: We did not have a control group. Further studies are required to demonstrate the relevance of these 2 imaging techniques (epiduroscopy and MRI) in terms of detecting epidural fibrosis in patients with FBSS.  CONCLUSIONS: Epiduroscopic imaging seems to be more sensitive than MRI in detecting grade I epidural fibrosis in patients with FBSS. Thus, the possibility of low-grade epidural fibrosis as a source of pain after back surgery, should be kept in mind in normally reported MRIs. Treatment should be planned accordingly.