At What Surgical Cost Does Transforaminal Lumbar Interbody Fusion Become Less Cost-Effective Than Posterolateral Fusion for Spondylolisthesis?

Comments by lead author Leah Y. Carreon MD, MSc; Russel C. Huang, MD; and Don Young Park, MD

postoperative lateral x-ray transforaminal lumbar interbody fusionWhile transforaminal lumbar interbody fusion (TLIF) has become the most commonly used fusion technique for lumbar degenerative disorders, the factors that drive the cost-effectiveness of this procedure have not been established. New findings published in JNS Spine suggest that the cost of TLIF per quality-adjusted life years (QALYs) versus posterolateral fusion (PSF) in the treatment of spondylolisthesis depends on the measure of health utility selected, durability of the intervention, readmission rates, and the accuracy of cost assumptions.

The study was designed to determine the threshold at which the increased surgical cost of TLIF for the treatment of spondylolisthesis would be considered cost-prohibitive relative to PSF using either EQ-5D or Short Form–6D (SF-6D) scores to calculate QALYs. The researchers used data from the National Neurosurgery Quality and Outcomes Database (N2QOD) to identify 101 patients with spondylolisthesis who underwent PSF, and 101 propensity score matched patients who underwent TLIF for the same condition. The procedures involved a 1-level or 2-level posterior lumbar fusion with or without an interbody graft.

"The implication is that depending on what utility value is used to determine quality-adjusted life years (QALY, EQ5D, SF-6D) and what Willingness-to-Pay (WTP) threshold is used to determine cost-effectiveness, decisions on cost-effectiveness will change," lead author Leah Y. Carreon MD, MSc, told SpineUniverse. Dr. Carreon is Clinical Research Director at Norton Leatherman Spine Center, in Louisville, Kentucky.

Clinical Outcomes
The two groups were similar in terms of operative time and blood loss, hospital length of stay, and 30-day and 90-day readmission rate. In addition, both groups showed improvement over baseline scores for leg pain, ODI, EQ-5D, and SF-6D at 3 and 12 months after surgery. In contrast, TLIF was associated with greater improvement in mean ODI score compared with PSF (30.4 vs 21.1; P=0.001).

Outcomes Varied by Measure of Health Utility
Greater health utility gains were found with TLIF than PSF, but these gains were greater when scores from the SF-6D (0.16 vs 0.11; P=0.001) rather than the EQ-5D questionnaire (mean change, 0.25 vs 0.22; P=0.415) were used.

The increased surgical cost at which TLIF becomes less cost-effective than PSF varied from $1,570 to $4,830, depending on which cost-effectiveness threshold and health utility value were used, Dr. Carreon and colleagues noted. In addition, they concluded that the cost per QALY "depends on the measure of health utility selected, durability of the intervention, readmission rates, and the accuracy of cost assumptions.

Dr. Carreon hopes that the findings will "increase awareness of the need to show treatment effectiveness before fully adapting a new technology and increase understanding of the metrics used in cost-effectiveness studies."


Russel C. Huang, MD
Director of the Spine Surgery Clinic
Hospital for Special Surgery
New York, NY

It is difficult to draw firm conclusions from this study as the analysis is based upon a fundamentally flawed premise. The authors used propensity matching to best ensure that the two cohorts (PSF and TLIF) were as similar as possible, but the majority of surgeons are choosing PSF or TLIF based on patient characteristics (such as severity of foraminal collapse or presence of discogenic pain) that are not accounted for in the propensity matching process. This flaw in analysis would tend to underestimate the value of TLIF.

This study provides weak support to the TLIF procedure, but as outlined above the study likely underestimates the clinical and economic value of TLIF in appropriately selected patients.

Our community of surgeons and our patients already understand the value and effectiveness of well-indicated spinal interventions, but studies such as this will become increasingly important going forward as payers demand data backing up the value of spinal surgery.

Don Young Park, MD
Assistant Clinical Professor of Orthopaedic Surgery
UCLA Spine Center
Santa Monica, CA

This retrospective database study with short-term follow-up confirms the findings of multiple clinical studies that lumbar fusion surgery is very successful when performed in select patients. At the 1-year point after surgery, both types of lumbar fusion surgeries had similar clinical outcomes.

TLIF patients had greater clinical improvements in 2 out of the 3 outcome measures as compared to PSF patients. These outcome measures reflect how patients actually do after surgery and indicate that both surgeries are very successful, with the edge given to TLIF.

However, when you look at the cost associated with the different procedures and associated improvements in quality of life, TLIF is more cost prohibitive as compared to PSF. This stands to reason since TLIF involves an expensive implant in addition to the pedicle screws that both procedures utilize to accomplish the goals of surgery. The authors argue that TLIF may not be cost effective when compared to PSF.

This study will likely make surgeons, insurance companies, and hospital administrators think twice about approving and performing TLIF fusion surgeries. Surgeons may be compelled to perform PSF over TLIF, especially in this day and age of quality and cost-reduction. Payers may only pay for the PSF and not the interbody portion of the procedure, which is more time consuming and carries higher risk. The costs may be passed down to the patient who may be left with an exorbitant hospital bill.
However, multiple studies in the literature demonstrate that interbody fusions have greater fusion rates as compared to PSF due to the increased surface area within the disc space. Multiple studies have shown that accomplishing solid fusion is the key to long-term clinical success and there are significant costs to treating symptomatic nonunions. The initial incremental cost of TLIF may potentially be offset by the reduced nonunion rates in the long term with possibly fewer reoperations, less pain and disability, and reduced burden to the healthcare system.

One advantage of this study is that they have a relatively high number of patients since it is a database study. Yet there are significant disadvantages of this type of study since the research questions were asked after the data was collected and analyzed—ie, the database was prospectively collected yet the data was retrospectively analyzed, which can bias the results significantly. In addition, a common problem with cost-effectiveness studies is that certain assumptions of cost are used for the calculations, and these assumptions could change the results and conclusions.

Updated on: 07/28/16
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