Does the drain placement technique affect the amount of postoperative spinal epidural hematoma after microendoscopic decompressive laminotomy for lumbar spinal stenosis?

Objective: To prospectively evaluate with magnetic resonance imaging (MRI), the relationship between the distance from the incision of the drain output location and postoperative spinal epidural hematoma (SEH) in patients performed with microendoscopic decompressive laminotomy (MEDL) for lumbar spinal stenosis. Methods: Between January 2016 and June 2018, three different kinds of drain placement techniques, according to the drain output location, were performed to a total of 184 patients after MEDL for single-level spinal stenosis. The location of the drain output was within the incision in group 1, 1 cm lateral of the incision in group 2, and 5 cm lateral of the incision in group 3. At 24 h postoperatively, before removal of the drain, MRI examination was carried out in patients. A specific classification was developed by the authors to measure SEH, and the groups were evaluated by comparison. Results: The mean postoperative dural sac cross-sectional area was 1.73 cm2 (standard deviation (SD): 0.711) in group 1, 1.66 cm2 (SD: 0.732) in group 2, and 1.52 cm2 in group 3 (SD: 0.841).The mean cross-sectional area of the postoperative hematoma was 1.45 cm2 (SD: 1.007) in group 1, 1.57 cm2 (SD: 1.053) in group 2, and 2.11 cm2 (SD: 1.024) in group 3. Four grades were defined according to the specific classification. According to this classification, grades C and D postoperative hematomas were determined at a statistically significantly higher rate in group 3 patients (drain output 5 cm lateral from the incision) compared to the other groups (p = 0.000). No significant difference was determined between groups 1 and 2 in respect of hematoma classification. Conclusion: In conclusion, it was determined that better drainage was provided in groups 1 and 2, where the drain output location was in the incision or close to it.