Risk Factors for Incidence of Postoperative Spinal Epidural Hematoma Following Multilevel Microendoscopic Laminectomy.

INTRODUCTION: Due to the narrow portal of entry, microendoscopic laminectomy (MEL) is associated with a risk of postoperative spinal epidural hematoma (POSEH). This risk might be higher when performing multiple-level (m-) MEL. The purpose of this study is to clarify the incidence rate of POSEH following single-level (s-) and m-MEL by each interlaminar level and identify the risk factors for POSEH following m-MEL. METHODS: A total of 379 patients underwent MEL of the lumbar spine (s-MEL, n=141; m-MEL, n=238). We determined the incidence of POSEH following s-MEL and m-MEL by each interlaminar level. For m-MEL, we clarified the correlation between POSEH and possible risk factors, such as operative findings, the sequence of operated interlaminar levels, and the preoperative cross-sectional dural area (CSA) on magnetic resonance imaging. RESULTS: The incidence rate at L2/3 was significantly higher than that at L3/4 and L4/5. Patients who underwent L2/3 decompression at the end of the procedure showed a higher incidence of POSEH at the L2/3 level. Preoperative spinal stenosis was associated with POSEH at the L2/3 level, and CSA of 56 mm2 was a predictive factor for POSEH. Logistic regression analysis revealed that both were significant risk factors. CONCLUSIONS: In patients undergoing m-MEL, the incidence of POSEH is highest at the L2/3 level, and treatment of the L2/3 level at the end of the procedure and the presence of spinal stenosis are risk factors for POSEH.