Posterior lumbar epidural fat commonly had been considered a simple space-filling tissue. Anatomic studies on posterior epidural space and its contents are few, including semifluid property. In other words, there has not been studied thoroughly regarding the significance and role of posterior epidural fat in lumbar spine. In adults, epidural fat situated in the posterior triangle limited by the lamina, the ligamentum flavum, and the posterior surface of thecal sac. The fat tissue was covered by a thin membrane of connective tissue, which were free under this layer. The anterior surface of this membrane lay close to the dura mater without any attachment.

To date, the epidural fat has been resected routinely by pituitary forcep and suction drainage during posterior lumbar surgery. However, the investigators focused on the role of epidural fat, which might be associated with postoperative outcome. The investigators thought that this peculiar character, epidural fat, should be caused by certain etiologies. In general, each tissue, such as epidural fat, has its inherited features and significance, thereby the epidural fat has also specific role. However, there has not been fully studies regarding it. Thus, the investigators aimed to evaluate the impact of the posterior epidural fat on the postoperative outcomes such as pain intensity and functional outcomes by whether the epidural fat would be resected or not during posterior decompressive surgery. The investigators hypothesized that the epidural fat would be associated with postoperative pain intensitive, functional outcomes, and complications of the surgery such as failed back surgery syndrome. In this study, new device for resection of epidural fat was not utilized, but just resected with conventional devices such as pituitary forcep.

Inclusion Criteria:

• patients with a lumbar spinal stenosis, which were diagnosed using lumbar spine radiographs and magnetic resonance images (MRI) that corresponded to clinical manifestations and physical examinations
• patients who underwent one-level posterior decompression
• patients aging between 20 and 80 years
• patients who volunteered for this study with written consent
• patient who were followed-up for one year or more

Exclusion Criteria:

• fractures, infection, or tumors in the lumbar spine
• patients with hemorrhagic disorders such as hemophilia and thrombocythemia
• patient with a follow-up period of less than one year
• patients who are not suitable for this study judged by the principal investigator