title: The cost-effectiveness of interbody fusions versus posterolateral fusions in 137 patients with lumbar spondylolisthesis.
abstract: BACKGROUND
  Reimbursements for interbody fusions have declined recently because of their questionable cost-effectiveness.
  
  
  OBJECTIVE
  A Markov model was adopted to compare the cost-effectiveness of posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (/TLIF) versus noninterbody fusion and posterolateral fusion (PLF) in patients with lumbar spondylolisthesis.
  
  
  METHODS
  Decision model analysis based on retrospective data from a single institutional series.
  
  
  METHODS
  One hundred thirty-seven patients underwent first-time instrumented lumbar fusions for degenerative or isthmic spondylolisthesis.
  
  
  METHODS
  Quality of life adjustments and expenditures were assigned to each short-term complication (durotomy, surgical site infection, and medical complication) and long-term outcome (bowel/bladder dysfunction and paraplegia, neurologic deficit, and chronic back pain).
  
  
  METHODS
  Patients were divided into a PLF cohort and a PLF plus PLIF/TLIF cohort. Anterior techniques and multilevel interbody fusions were excluded. Each short-term complication and long-term outcome was assigned a numerical quality-adjusted life-year (QALY), based on time trade-off values in the Beaver Dam Health Outcomes Study. The cost data for short-term complications were calculated from charges accrued by the institution's finance sector, and the cost data for long-term outcomes were estimated from the literature. The difference in cost of PLF plus PLIF/TLIF from the cost of PLF alone divided by the difference in QALY equals the cost-effectiveness ratio (CER). We do not report any study funding sources or any study-specific appraisal of potential conflict of interest-associated biases in this article.
  
  
  RESULTS
  Of 137 first-time lumbar fusions for spondylolisthesis, 83 patients underwent PLF and 54 underwent PLIF/TLIF. The average time to reoperation was 3.5 years. The mean QALY over 3.5 years was 2.81 in the PLF cohort versus 2.66 in the PLIFo/TLIF cohort (p=.110). The mean 3.5-year costs of $54,827.05 after index interbody fusion were statistically higher than that of the $48,822.76 after PLF (p=.042). The CER of interbody fusion to PLF after the first operation was -$46,699.40 per QALY; however, of the 27 patients requiring reoperation, the incident (reoperation) rate ratio was 7.89 times higher after PLF (2.91, 26.67). The CER after the first reoperation was -$24,429.04 per QALY (relative to PLF). Two patients in the PLF cohort required a second reoperation, whereas none required a second reoperation in the PLIF/TLIF cohort. Taken collectively, the total CER for the interbody fusion is $9,883.97 per QALY.
  
  
  CONCLUSIONS
  The reoperation rate was statistically higher for PLF, whereas the negative CER for the initial operation and first reoperation favors PLF. However, when second reoperations were included, the CER for the interbody fusion became $9,883.97 per QALY, suggesting moderate long-term cost savings and better functional outcomes with the interbody fusion.
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA; Spinal Column Biomechanics and Surgical Outcomes Laboratory, Johns Hopkins University School of Medicine, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Bydon
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA; Spinal Column Biomechanics and Surgical Outcomes Laboratory, Johns Hopkins University School of Medicine, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Macki
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Abt
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Witham
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Wolinsky
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA; Spinal Column Biomechanics and Surgical Outcomes Laboratory, Johns Hopkins University School of Medicine, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Ziya L
authors.initials: ZL
authors.lastname: Gokaslan
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA; Spinal Column Biomechanics and Surgical Outcomes Laboratory, Johns Hopkins University School of Medicine, 600 N. Wolfe St, Baltimore, MD 21287, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Bydon
authors.affiliation: Department of Neurosurgery, Johns Hopkins University School of Medicine, Meyer 7-109, 600 N. Wolfe St, Baltimore, MD 21287, USA. Electronic address: dsciubb1@jhmi.edu.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sciubba
mesh_terms: D000368:Aged; D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D005260:Female; D017048:Health Care Costs; D005102:Health Expenditures; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008390:Markov Chains; D008875:Middle Aged; D019057:Quality-Adjusted Life Years; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects / Q000191:economics / Q000379:methods*; D013168:Spondylolisthesis / Q000601:surgery*
keywords: Cost-effectiveness; Interbody; Lumbar; PLIF; Spondylolisthesis; TLIF