title: Prospective study of postoperative lumbar epidural hematoma: incidence and risk factors.
abstract: METHODS
  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.
  
  
  BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Twin Cities Spine Center, Minneapolis, MN, USA. mjsokolowski@yahoo.com
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Sokolowski
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Garvey
authors.forename: John
authors.initials: J
authors.lastname: Perl
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Sokolowski
authors.forename: Woojin
authors.initials: W
authors.lastname: Cho
authors.forename: Amir A
authors.initials: AA
authors.lastname: Mehbod
authors.forename: Daryll C
authors.initials: DC
authors.lastname: Dykes
authors.forename: Ensor E
authors.initials: EE
authors.lastname: Transfeldt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D046748:Hematoma, Epidural, Spinal / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D019637:Orthopedic Procedures / Q000009:adverse effects*; D011183:Postoperative Complications; D011446:Prospective Studies; D012307:Risk Factors; D013118:Spinal Cord Diseases / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D013131:Spine / Q000473:pathology / Q000601:surgery*