Analysis of Subdural Injection During Lumbar Interlaminar Epidural Injection in Failed Back Surgery Syndrome

Persistent or recurrent back and leg pain following spinal surgery, known as failed back surgery syndrome (FBSS), significantly limits daily life activities. A lumbar epidural injection can reduce adhesions, inflammation, and nerve compression, although the epidural space can be distorted due to dura mater and epidural tissues changes after spinal surgery. This study analyzed subdural injection during lumbar epidural injection in FBSS patients. We retrospectively analyzed data from 155 patients who received a lumbar interlaminar epidural injection to manage FBSS. We grouped the patients based on the injected contrast medium appearance in the subdural (group S) or epidural spaces (group E) in fluoroscopic contrast images. Demographic, clinical, surgical and fluoroscopic data were recorded and evaluated, as were the pain scores before and after injection. There were 59 patients (38.1%) in the subdural group. Injection distance from the surgery level differed between the groups. Risk of subdural injection at level 1 distance from the surgery level had an odds ratio of 0.374, and at level ≥2, it was 0.172, when compared to level 0. Subdural incidence differed with the distance from surgical site. Physicians should strive to reduce subdural incidence when the injection is planned at surgery site in FBSS.