Does a Drain Tube Influence the Postoperative Epidural Haematoma for Lumbar Biportal Endoscopic Surgery?

Inclusion Criteria: All patients with two level lumbar stenosis and neurogenic claudication with or without lumbar radiculopathy were eligible for inclusion. Exclusion Criteria: Patients were excluded if radiography revealed lumbar instability (motion of \>3mm at the level of listhesis), if they had had previous lumbar spinal surgery, or they had American Society of Anesthesiologists (ASA) class Ⅳ or severe systemic disease.