title: Patient-specific factors affecting hospital costs in lumbar spine surgery.
abstract: OBJECTIVE
  Health care-related costs after lumbar spine surgery vary depending on procedure type and patient characteristics. Age, body mass index (BMI), number of spinal levels, and presence of comorbidities probably have significant effects on overall costs. The present study assessed the impact of patient characteristics on hospital costs in patients undergoing elective lumbar decompressive spine surgery.
  
  
  METHODS
  This study was a retrospective review of elective lumbar decompression surgeries, with a focus on specific patient characteristics to determine which factors drive postoperative, hospital-related costs. Records between January 2010 and July 2012 were searched retrospectively. Only elective lumbar decompressions including discectomy or laminectomy were included. Cost data were obtained using a database that allows standardization of a list of hospital costs to the fiscal year 2013-2014. The relationship between cost and patient factors including age, BMI, and American Society of Anesthesiologists (ASA) Physical Status Classification System grade were analyzed using Student t-tests, ANOVA, and multivariate regression analyses.
  
  
  RESULTS
  There were 1201 patients included in the analysis, with a mean age of 61.6 years. Sixty percent of patients in the study were male. Laminectomies were performed in 557 patients (46%) and discectomies in 644 (54%). Laminectomies led to an increased hospital stay of 1.4 days (p < 0.001) and increased hospital costs by $1523 (p < 0.001) when compared with discectomies. For laminectomies, age, BMI, ASA grade, number of levels, and durotomy all led to significantly increased hospital costs and length of stay on univariate analysis, but ASA grade and presence of a durotomy did not maintain significance on multivariate analysis for hospital costs. For a laminectomy, patient age ≥ 65 years was associated with a 0.6-day increased length of stay and a $945 increase in hospital costs when compared with patient age < 65 years (p < 0.001). A durotomy during a laminectomy increased length of stay by 1.0 day and increased hospital costs by $1382 (p < 0.03). For discectomies, age, ASA grade, and durotomy were significantly associated with increased hospital costs on univariate analysis, but BMI was not. Only age and presence of a durotomy maintained significance on multivariate analysis. There was a significant increase in hospital length of stay in patients undergoing discectomy with increasing age, BMI, ASA grade, and presence of a durotomy on univariate analysis. However, only age and presence of a durotomy maintained significance on multivariate analysis. For discectomies, age ≥ 65 years was associated with a 0.7-day increased length of stay (p < 0.001) and an increase of $931 in postoperative hospital costs (p < 0.01) when compared with age < 65 years.
  
  
  CONCLUSIONS
  Patient factors such as age, BMI, and comorbidities have significant and measurable effects on the postoperative hospital costs of elective lumbar decompression spinal surgeries. Knowledge of how these factors affect costs will become important as reimbursement models change.
authors.affiliation: Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ross C
authors.initials: RC
authors.lastname: Puffer
authors.affiliation: Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ryan
authors.initials: R
authors.lastname: Planchard
authors.affiliation: Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Grant W
authors.initials: GW
authors.lastname: Mallory
authors.affiliation: Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota.
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Clarke
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D019299:Decompression, Surgical / Q000191:economics*; D017586:Diskectomy / Q000191:economics; D005260:Female; D017048:Health Care Costs; D017721:Hospital Costs; D006801:Humans; D007796:Laminectomy / Q000191:economics*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000191:economics
keywords: ASA = American Society of Anesthesiologists; BMI = body mass index; cost; lumbar; outcomes; spine; surgery