Budget Impact Analysis of Minimally Invasive versus Open Transforaminal Lumbar Interbody Fusion for Lumbar Degenerative Disease: A European Hospital Perspective

Figures & data

Table 1 Model Input Parameters

Input Parameters	Base Case	Base Case Distribution for PSA	Scenario Analysis	Scenario Distribution for PSA
LOS O-TLIF (days)^a	8.06 days^b	Gamma (α=1956.95, β=0.004)	8.30 days^c	Gamma (α=2052.61, β=0.004)
LOS reduction (MI-TLIF vs O-TLIF; days)	2.2 days^b	Normal (α=2.2, β=0.26)	1.95 days^c	Normal (α=1.95, β=0.40)
Blood loss (O-TLIF; mL)^a	434.17 mL^b	Gamma (α=2050.78, β=0.212)	624.51^c	Gamma (α=1662.50, β=0.38)
Blood loss reduction (MI-TLIF vs O-TLIF; mL)	200 mL^b	Normal (α=200, β=55)	341.89 mL^c	Normal (α=341.89, β=44.29)
Number of trays requiring sterilization in MI-TLIF	1.00^d	Normal (α=1, β=1)	1.00^d	Normal (α=1, β=1)
Number of trays requiring sterilization in O-TLIF	5.00^d	Normal (α=5, β=1)	5.00^d	Normal (α=5, β=1)
OR time (O-TLIF; minutes)^a	N/A	N/A	177.90 ^c	Gamma (α= 11,291.80, β=0.02)
OR time increase (MI-TLIF vs O-TLIF; minutes)	N/A	N/A	+6.17 minutes^c	Normal (α=6.17, β=21.73)
Complication rate (O-TLIF; %)^a	N/A	N/A	14.2% ^c	Beta (α=73, β=441)
Complication rate odds ratio (MI-TLIF vs O-TLIF; %)	N/A	N/A	0.7^c	Log-normal (α= −0.36, β=0.19)

Notes: ^a Calculated as weighted averages based on the sample size and mean value reported by individual studies informing the respective meta-analysis outcome. ^bSource: Miller et al, (2020).^{18 c}Source: Hammad et al, (2019).^{10 d}Source: MI-TLIF: Johnson & Johnson Lista componenti kit (List of components): Viper Prime™ System;¹⁴ O-TLIF: Johnson & Johnson Lista componenti kit (List of components): Expedium™ System.¹³.

Abbreviations: LOS, length of stay; MI-TLIF, minimally-invasive transforaminal lumbar interbody fusion; N/A, not applicable; OR, operating room; O-TLIF, open transforaminal lumbar interbody fusion.

Table 2 Costs Included in the Model

Cost Type	Reported Value (€) and Year	2023 (€)	Distribution and Parameters for PSA
LOS cost per day	674^a (2004)	978.53	Gamma (α=96.04, β=10.19)
RBC cost per unit for blood loss	288^b (2020)	337.62	Gamma (α=96.04, β=3.52)
Sterilization cost per tray^c	58^d (2015)	70.58	Gamma (α=96.04, β=0.74)
Device cost difference between O-TLIF and MI-TLIF	530.20^e	N/A ^f	Normal (α=530.2, β=54.10)
OR cost per minute (scenario analysis only)	24^g (2013)	29.60	Gamma (α=96.04, β=0.31)
Complication cost (scenario analysis only)	441^g (2013)	543.87	Gamma (α=96.04, β=5.66)

Notes: ^aSource: MEF (2007).^{22 b}Beverina et al, (2020).^{23 c}Value was obtained from a French study due to the lack of Italian data. ^dBouthors et al, (2019).^{25 e}Johnson and Johnson (2018).^{24 f}Device costs and differences between them are typically not inflated. ^gVertuani et al, (2015).²

Abbreviations: LOS, length of stay; MI-TLIF, minimally-invasive transforaminal lumbar interbody fusion; MEF, Ministero dell’Economia e delle Finanze; N/A, not applicable; O-TLIF, open transforaminal lumbar interbody fusion; RBC, red blood cell.

Table 3 Base Case results in 2023 Euros

Cost Type	Deterministic			Probabilistic
	MI-TLIF	O-TLIF	Incremental Cost (2023 €)	Incremental Cost (95% CR)
Hospital length of stay	€573,325	€788,602	- €215,277	- €215,896 (- €218,019 to - €213,772)
RBC transfusion for blood loss	€16,881	€33,762	- €16,881	- €19,960^a (- €20,566 to - €19,354)
Surgical Tray Sterilization	€7058	€35,290	- €28,232	- €28,189 (- €28,546 to - €27,831)
Device	€53,020	-	€53,020	€53,018 (€52,679 to €53,358)
Total Cost	€650,284	€857,654	- €207,370	- €211,026 (- €213,327 to - €208,725)
Cost per patient	€6503	€8577	- €2074	- €2110 (- €2133 to - €2087)

Note: ^aNote that since both the differences in number of transfusions and costs of RBC bags were varied with every iteration of the probabilistic analysis, the PSA results differ relatively more from the deterministic base case compared to the PSA and deterministic results for other outcomes.

Abbreviations: CR, credible interval; MI-TLIF, minimally-invasive transforaminal lumbar interbody fusion; O-TLIF, open transforaminal lumbar interbody fusion; RBC, red blood cell.

Figure 1 Base case analysis. (A) Box plot showing total cost savings for MI-TLIF versus O-TLIF based on 1000 PSA iterations. (B) Histogram of the distribution of total cost savings for MI-TLIF versus O-TLIF according to 1000 PSA iterations.

Notes: x=mean; middle line = median; box = Q1-Q3; whiskers = ± 1.5 IQR.

Abbreviations: IQR, interquartile range; PSA, probabilistic sensitivity analysis.

Figure 2 Tornado diagram showing the influence of model parameters in a one-way sensitivity analysis of the base case.

Abbreviations: LOS, length of stay; MI-TLIF, minimally invasive transforaminal lumbar interbody fusion; O-TLIF, open transforaminal lumbar interbody fusion; RBC, red blood cell.

Table 4 Scenario Analysis Results

Cost Type	Deterministic			Probabilistic
	MI-TLIF	O-TLIF	Incremental Cost (2023 €)	Incremental Cost (95% CR)
Hospital length of stay	€621,367	€812,180	- €190,813	- €189,905 (- €192,520 to - €187,291)
RBC transfusion for blood loss	€16,881	€33,762	- €16,881	- €12,319^a (- €12,869 to - €11,769)
Tray sterilization	€7058	€35,290	- €28,232	- €28,120 (- €28,493 to - €27,748)
Device	€53,020	-	€53,020	€53,412 (€53,072 to €53,751)
OR time	€544,847	€526,584	€18,263	€16,919 (€12,873 to €20,966)
Complications	€5647	€7723	- €2076	- €2023 (- €2084 to - €1962)
Total Cost	€1,248,819	€1,415,539	- €166,719	- €162,036 (- €166,864 to - €157,209)
Cost per patient	€12,488	€14,155	- €1667	- €1620 (- €1.669 to - €1572)

Note: ^aNote that since both the differences in number of transfusions and costs of RBC bags were varied with every iteration of the probabilistic analysis, the PSA results differ relatively more from the deterministic base case compared to the PSA and deterministic results for other outcomes.

Abbreviations: CR, credible interval; MI-TLIF, minimally-invasive transforaminal lumbar interbody fusion; OR, operating room; O-TLIF, open transforaminal lumbar interbody fusion; RBC, red blood cells.

Figure 3 Scenario analysis. (A) Box plot showing total cost savings for MI-TLIF versus O-TLIF based on 1000 PSA iterations. (B) Histogram of the distribution of total cost savings for MI-TLIF versus O-TLIF according to 1000 PSA iterations.

Notes: x=mean; middle line = median; box = Q1-Q3; whiskers = ± 1.5 IQR.

Abbreviation: PSA, probabilistic sensitivity analysis.

Figure 4 Tornado diagram showing the influence of model parameters in a one-way sensitivity analysis of the scenario analysis.

Abbreviations: LOS, length of stay; MI-TLIF, minimally invasive transforaminal lumbar interbody fusion; OR, operating room; O-TLIF, open transforaminal lumbar interbody fusion; RBC, red blood cell.

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