Article Figures & Data
Figures
- Fig. 1
Markov Models for Conservative Care (CC) Strategy, Spacer Strategy, and Decompressive Surgery (DS) Strategy.
- Fig. 2
QALYs gained at three months and 24 months.
- Fig. 3
Conservative Care Strategy one-variable sensitivity analysis.
- Fig. 4
Spacer Strategy one-variable sensitivity analysis.
- Fig. 5
Decompressive Surgery Strategy one-variable sensitivity analysis.
- Fig. 6
Decompressive Surgery Strategy one-variable sensitivity analysis.
- Fig. 7
Cost-effectiveness plane: Increase in cost versus increase in utility gained, Spacer and Decompressive Surgery (DS) Strategies compared to the Conservative Care (CC) Strategy.
Tables
Characteristic CC * Spacer† DS‡ Comparison p-value§ CC v Spacer CC v DS Spacer v DS Number of patients 100 189 129 NA NA NA Age, mean (SD) 58 (12) 66 (9) 64 (11) <0.05 <0.05 NS Male, % 40 58 59 <0.05 <0.05 NS ODI, mean (SD) 57 (19) 39 (13) 47 (14) <0.05 <0.05 <0.05 SF-12 PCS, mean (SD) 31.4 (8.1) 29.2 (8.4) 26.7 (9.4) <0.05 <0.05 <0.05 SF-12 MCS, mean (SD) 49.2 (12.1) 49.9 (13.1) 48.2 (11.2) NS NS NS 1 Level treated, % NA 52 45 NS NS NS 2 Levels treated, % NA 48 55 SD: Standard deviation.
↵* CC: Conservative Care, from Parker et al. 2014. Results from spondylolisthesis and stenosis patients were combined.
↵† Spacer: from ISISS trial, Superion patients.
↵‡ DS: Decompressive Surgery without fusion, from institutional registry.
↵§ For continuous variables, a two sample Z-test was used for the pairwise comparisons. For categorical variables, Fisher's exact test was used. A p-value of 0.05 was considered statistically significant. No corrections for multiplicity were applied.
Treatments CC Spacer DS Variable Base Case Base Case Base Case Failure rate, quarterly 4.3% 2.7% 1.2% 1 Level NA 50.0% 50.0% 2 Levels NA 50.0% 50.0% Adverse event* NA 0.0% 5.4% Inpatient rehabilitation NA 0.0% 3.9% Fusion, secondary treatmentx 31% Probability of utilization - Qtr of Procedure Healthcare NA 45.2% 76.2% Medications NA 94.4% 94.4% Diagnostics NA 22.2% 22.2% Probability of utilization - FU Quarters Healthcare 94.0% 13.1% 12.9% Medications 100.0% 64.3% 64.3% Diagnostics 86.0% 8.8% 8.8% Costs Procedure 1 Level $7,367 $7,883 2 Levels $7,683 $8,155 1 Level, fusionx NA $26,118 2 Levels, fusionx NA $27,662 Anesthesiology NA $386 $454/$567# Inpatient rehabilitation NA NA $9,100 Qtr of Procedure Healthcare $662 $774 Medications $334 $334 Diagnostics $333 $333 FU Quarters Healthcare $289 $665 $1,060 Medications $498 $337 $337 Diagnostics $162 $870 $870 Adverse Event NA $6,770 QALY gained‡ Baseline to 3 mo 0.008 0.111 0.091 3 mo - 6 mo 0.016 0.144 0.173 6 mo - 9 mo 0.016 0.144 0.162 9 mo - 12 mo 0.016 0.144 0.155 After 12 mo 0.016 0.144 0.151 ↵* Adverse Events (AE) that generate additional reimbursement outside of the global payment. Healthcare includes non-surgeon physician visits, physical therapy, chiropractic care, acupuncture. Medications include narcotics, muscle relaxants, NSAIDs, and oral steroids. Diagnostics include MRI scans, CT scans, x-rays, spine injections, and EMGs. Superion patients assumed to have the same level of utilization for non-surgeon physician visits, medications, and diagnostics as decompressive surgery patients.
↵x DS with fusion was received by a portion of patients after DS or Spacer failure.
↵# Anesthesiology rate for DS without fusion / Anesthesiology rate for DS with fusion.
↵‡ QALY gained is an annual amount; one-fourth of the value is accumulated each quarter.
One-Variable Sensitivity Analysis Probabilistic Sensitivity Analysis Variable Lower Base case Upper Distribution (Parameters) Failure CC 0.028 0.043 0.060 Beta (mean=.043, SE=.008) Spacer 0.020 0.027 0.036 Beta (mean=.027,SE=.004) DS 0.004 0.012 0.037 Beta (mean=.012,SE=.008) DS AE rate 0.022 0.054 0.099 Beta (α = 7, β = 122) IRF discharge rate 0.013 0.039 0.078 Beta (α = 5, β = 124) Proportion 1 Level 0.25 0.50 0.75 Triangular (0.25,0.50,0.75) Fusion rate 0.17 0.31 0.47 Beta (α = 11, β = 24) DS after CC failure 0.80 0.90 1.00 Triangular (0.80,0.90,1.00) Utility Increase CC 0.000 0.016 0.030 Fixed Spacer 0.120 0.144 0.168 Normal (0.144, 0.013) DS, 3 mo 0.154 0.181 0.207 Normal (0.181, 0.014) DS, 12 mo 0.124 0.151 0.179 Normal (0.151, 0.014)
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