Prospective study of postoperative lumbar epidural hematoma: incidence and risk factors.

Study Design: Prospective clinical series.

Objective: To determine the incidence, volume, and extent of postoperative epidural hematoma resulting in thecal sac compression, and to identify risk factors correlated with measured hematoma volumes.

Summary Of Background Data: Risk factors for postoperative hematoma development have been retrospectively determined in small populations of symptomatic patients. A prospective study of hematoma characteristics and associated risk factors in a consecutive series of patients could significantly enhance our understanding of postoperative hematoma.

Methods: Preoperative magnetic resonance imaging and clinical data on 13 pre- and intraoperative risk factors were prospectively collected on 50 consecutive patients undergoing lumbar decompression surgery with or without fusion. Postoperative magnetic resonance imagings were performed within 2 to 5 days of surgery. Thecal sac cross-sectional area was calculated at each disc space. Relative thecal sac compression due to hematoma was calculated at all levels where postoperative cross-sectional area was smaller than preoperative. Hematoma volumes were calculated. Multivariate analysis identified risk factors associated with postoperative hematoma volume.

Results: After decompression, 58% of patients developed epidural hematoma of sufficient magnitude to compress the thecal sac beyond its preoperative state at one or more levels. None developed new postoperative neurologic deficits. A mean of 1.4 levels were decompressed. Hematoma extended over a mean of 1.9 levels. Maximal thecal sac compression due to hematoma occurred at an adjacent, nondecompressed level in 28% of patients. Multivariate analysis found age greater than 60, multilevel procedures, and preoperative international normalized ratio to be associated with larger hematoma volumes.

Conclusion: Lumbar decompression surgery results in a 58% incidence of asymptomatic compressive postoperative epidural hematoma. Adjacent level compression by hematoma occurs in 28% of patients. Advanced age, multilevel procedures, and international normalized ratio are independently associated with postoperative hematoma volume.