Editorial: Cost-effectiveness of transforaminal lumbar interbody fusion

Abstract

Adogwa et al.1 retrospectively evaluated 45 patients undergoing transforaminal lumbar interbody fusion (TLIF) for back and leg pain associated with Grade I degenerative spondylolisthesis. Conservative therapy had already failed after 6–12 months. Patients were entered into an electronic registry from which pre-, intra-, and perioperative data were recorded. Preoperative patient-reported metrics including EuroQol 5 Dimensions (EQ-5D), Oswestry Disability Index, and visual analog scale (VAS) scores were retrospectively assessed. Two-year resource utilization, occupational disability, and patient-reported outcomes were assessed by phone interview. Overall, the 2-year clinical outcomes were significantly improved for all outcome measures. The mean improvements in back pain VAS and leg pain VAS scores from baseline during the study period were 4.33 (95% CI 3.49–5.17) and 3.78 (95% CI 2.79–4.76), respectively. The mean improvements per patient in Oswestry Disability Index and EQ-5D US scaled index were 19.51 (95% CI 16.21–22.81) and 0.43 (95% CI 0.30–0.55), respectively. The cumulative health utility value gained over the 2-year interval following TLIF was 0.86 quality-adjusted life years (QALYs). Resource utilization was calculated from patient-reported use and institutional records and then confirmed by a retrospective analysis. The 2-year direct medical costs were analyzed based on Medicare national allowable payment amounts. The total direct costs comprised institutional, physician, and resource consumption Medicare fees. The method of cost calculation provides a strong estimate of the cost to the health care system. Indirect costs were calculated based on lost gross-of-tax wage rate on self-reported wages for patients and caregivers. Transforaminal lumbar interbody fusion was associated with a mean 2-year cost per QALY gained of $42,854. It is important to note that this study showed the 2-year cost of QALY gained for TLIF to treat degenerative lumbar spondylolisthesis ($42,854) compares favorably with other accepted surgical interventions such as total knee replacement ($59,262).4 Also, it is relevant to note that total hip arthroplasty in men older than 85 years has a cost of up to $80,000/QALY.2 These findings are important, and the cost analysis is very relevant in today’s era of evidence-based medicine. The authors have shown that TLIF represents a cost-effective treatment for patients with symptomatic Grade I spondylolisthesis. Limitations of this study include bias inherent to retrospective studies without a priori determination of follow-up assessment, recall bias regarding resource utilization, and lack of a comparison medical management cohort. However, performing such a study is unlikely because of the difficulty in evaluating cost and effectiveness ratios when there is high crossover between groups. This was a problem with the cost analysis from the Spine Patient Outcomes Research Trial (SPORT)5 in which a treatment bias existed for those in the medical management group (many of whom crossed over to surgery). Another limitation of this study is that there was no standardized system to define pseudarthrosis, the treatment of which would certainly impact cost significantly. Also, an increased length of follow-up would be useful to establish the effect of delayed complications such as adjacent-level disease that might not be seen in a 2-year study. Recently, an analysis of acute hospital charges comparing minimally invasive versus open posterior lumbar interbody fusion was published by Wang et al.6 Previous studies have also demonstrated a decreased length of stay with minimally invasive versus open TLIFs, but to date no large comparison cohort has explored whether minimally invasive TLIFs are more cost-effective.3 This would be an interesting area to explore. More comparisons of cost-effectiveness are needed in all areas of spinal surgery. Adogwa et al.1 discuss an important issue that will likely become an area of research focus within spine surgery and are congratulated on their excellent work.