title: Population-based trends in volumes and rates of ambulatory lumbar spine surgery.
abstract: METHODS
  Sequential cross-sectional study.
  
  
  OBJECTIVE
  To quantify patterns of outpatient lumbar spine surgery.
  
  
  BACKGROUND
  Outpatient lumbar spine surgery patterns are undocumented.
  
  
  METHODS
  We used CPT-4 and ICD-9-CM diagnosis/procedure codes to identify lumbar spine operations in 20+ year olds. We combined sample volume estimates from the National Hospital Discharge Survey (NHDS), the National Survey of Ambulatory Surgery (NSAS), and the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS) with complete case counts from HCUP's State Inpatient Databases (SIDs) and State Ambulatory Surgery Databases (SASDs) for four geographically diverse states. We excluded pregnant patients and those with vertebral fractures, cancer, trauma, or infection. We calculated age- and sex-adjusted rates.
  
  
  RESULTS
  Ambulatory cases comprised 4% to 13% of procedures performed from 1994 to 1996 (NHDS/NSAS data), versus 9% to 17% for 1997 to 2000 (SID/SASD data). Discectomies comprised 70% to 90% of outpatient cases. Conversely, proportions of discectomies performed on outpatients rose from 4% in 1994 to 26% in 2000. Outpatient fusions and laminectomies were uncommon. NIS data indicate that nationwide inpatient surgery rates were stable (159 cases/100,000 in 1994 vs. 162/100,000 in 2000). However, combined data from all sources suggest that inpatient and outpatient rates rose from 164 cases/100,000 in 1994 to 201/100,000 in 2000.
  
  
  CONCLUSIONS
  While inpatient lumbar surgery rates remained relatively stable for 1994 to 2000, outpatient surgery increased over time.
authors.affiliation: Center for Quality Improvement and Patient Safety, Agency for Healthcare Research and Quality, Rockville, MD 20850, USA. darryl.gray@ahrq.hhs.gov
authors.forename: Darryl T
authors.initials: DT
authors.lastname: Gray
authors.forename: Richard A
authors.initials: RA
authors.lastname: Deyo
authors.forename: William
authors.initials: W
authors.lastname: Kreuter
authors.forename: Sohail K
authors.initials: SK
authors.lastname: Mirza
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Heagerty
authors.forename: Bryan A
authors.initials: BA
authors.lastname: Comstock
authors.forename: Leighton
authors.initials: L
authors.lastname: Chan
mesh_terms: D000328:Adult; D000553:Ambulatory Care / Q000706:statistics & numerical data* / Q000639:trends*; D003430:Cross-Sectional Studies; D017586:Diskectomy / Q000706:statistics & numerical data / Q000639:trends; D006801:Humans; D007297:Inpatients / Q000706:statistics & numerical data; D007796:Laminectomy / Q000706:statistics & numerical data / Q000639:trends; D008159:Lumbar Vertebrae / Q000601:surgery*; D009985:Orthopedics / Q000706:statistics & numerical data* / Q000639:trends*; D013123:Spinal Fusion / Q000706:statistics & numerical data / Q000639:trends; D014481:United States