Cost-Effectiveness of Corrective Fusion Surgeries for Adult Spinal Deformities

A Comparison by Operative Method

Hideyuki Arima, MD, PhD; Tomohiko Hasegawa, MD, PhD; Yu Yamato, MD, PhD; Masashi Kato, BS; Go Yoshida, MD, PhD; Tomohiro Banno, MD, PhD; Shin Oe, MD, PhD; Yuki Mihara, MD, PhD; Hiroki Ushirozako, MD, PhD; Tomohiro Yamada, MD; Yuh Watanabe, MD; Koichiro Ide, MD; Keiichi Nakai, MD; Kenta Kurosu, MD; Yukihiro Matsuyama, MD, PhD

Disclosures

Spine. 2021;46(18):1249-1257. 

In This Article

Discussion

A thorough understanding of treatment costs is important in an evidence-based treatment approach. Value, defined as the quality of care compared to cost, has become an increasingly important factor in healthcare debates.[26,27] Herein, we summarized the medical costs and cost-effectiveness of three different surgical methods for ASD in patients with different backgrounds over 2 years postoperatively. The strength of this study is the mid-term outcome of 2 years postoperatively, but the follow-up rate is high at 78.6%; the follow-up assessment was based on whole spine standing radiograph and HRQOL questionnaires. Clinical outcomes significantly improved postoperatively in the Grade-2, three-column, and posterior corrective fusion with LLIF groups. The 2-year cumulative QALY improvement was higher in the LLIF group, although the difference was not significant. The LLIF group showed the highest medical expenses for the initial surgery. Over 2 years, the three-column and LLIF groups showed higher costs than the Grade-2 group. The overall cost/QALY 2 years after surgery was lowest in the LLIF group, although no statistical comparison was performed. The reference willingness to pay threshold was assumed to be USD 50,000 (JPY 5,000,000).[24,25] The cost/QALY of surgery for ASD 2 years after the procedure was well above this threshold, averaging about 10 times higher. This is consistent with previous reports where initial surgery for ASD could not be achieved 1 to 2 years after surgery as it resulted in high costs over the first 2 years.[11,28,29] The majority of ASD care costs stem from medical expenses related to the initial surgery. In this study, 29% of patients underwent revision surgery; consequently, the average medical expenses for the initial surgery were USD 72,240, and the average total medical expenses over the 2 years were USD 76,294. This means that the overall average increase 2 years after surgery was USD 4000, accounting for roughly 6% of the medical expenses for the initial surgery.

Nonetheless, clinical outcomes improved postoperatively, which was maintained for up to 5 years.[30] Therefore, index surgery for ASD is cost-effective 4 to 5 years after the initial surgery.[11] Importantly, for cost-effective ASD surgery, there should be no increased cost after the initial surgery. Revision surgeries are often due to rod fractures or PJF and must be reduced in the future.[31,32]

Between 2010 and 2014 in our institute, posterior corrective fusion with multiple Grade-2 osteotomy was performed in patients with scoliosis of the thoracolumbar/lumbar spine and poor global sagittal plane alignment.[12] This changed in 2014, after which we have performed staged surgeries with multilevel LLIF and posterior corrective fusions.[13] In posterior corrective fusion with multilevel LLIF, a large cage is used for lumbar kyphosis and scoliosis correction with an anterior approach. This enables correction and fusion for multilevel intervertebral spaces with lesser bleeding and shorter surgical time.[33] Therefore, the proportion of degenerative kyphoscoliosis is high in the Grade-2 and LLIF groups. Strategic changes over the study period for degenerative kyphoscoliosis in this study may be a potential bias. Nonetheless, for patients with rigid kyphosis of the thoracolumbar/lumbar spine, we primarily performed a three-column osteotomy.[12] Therefore, the rate of three-column osteotomy is high in degenerative kyphosis, kyphosis after vertebral body fracture, and iatrogenic kyphosis. In three-column osteotomy, a staged surgery was performed to mitigate surgical complications according to age and ASA classification.[34]

Overall, the complication rate did not vary among the three groups, but LLIF group showed more neurological complications owing to transient traction symptoms in the femoral nerve on the approach side, due to the lateral approach. Since it improved within 2 to 3 months after surgery, there was no revision surgery for the neurological deficit. However, it might have affected the cost of administered neuropathic pain medications. The revision surgery rate was higher in the three-column osteotomy group, associated with rod breakage.[35]

We sub-analyzed the cost-effectiveness of each surgical procedure, focusing only on degenerative kyphoscoliosis. The highest initial medical expenses were noted in the LLIF group. The S1 group had higher revision surgery rate, lower QALY improvement, and higher cost/QALY than the iliac group 2 years after the initial surgery. This is due to the high mechanical failure at the lumbosacral junction when S1 was selected as the LIV in the long corrective fusion for ASD,[36] and the mechanical failure at the lumbosacral junction may be associated with poor QALY improvement in the S1 group.

This study had limitations. First, medical expenses did not include outpatient costs. Future multicenter prospective studies should include postoperative outpatient consultation, pharmacy, and physiotherapy costs. Second, the study did not include indirect costs, including social loss due to the inability to work owing to ASD. Third, corrective fusion surgery for ASD has high complication and revision surgery rates. Revision surgery due to mechanical failure occurs even beyond 2 years after surgery; therefore, evaluating 2 years after surgery may not be sufficient. Fourth, implant suppliers were not unified in this study. Fifth, this study was conducted in Japan, and the Japanese healthcare system is different from that of North America and Europe. In Japan, universal insurance system is provided by the government and covers all citizens. Therefore, the results of this study may not directly apply in other countries. Sixth, cost/QALY calculations cannot be calculated for patients with zero QALY improvement. Cost/QALY was calculated by dividing the total cost of all cases in each group by the sum of QALY improvement. Therefore, it was impossible to compare groups using statistics on cost/QALY. The cost of zero QALY gain signifies very poor cost-effectiveness. However, this group included elderly patients, and the QOL would gradually decline with aging. Therefore, it would be necessary to compare each surgery group with a conservative treatment group to calculate the actual cost-effectiveness and determine whether a QALY gain of 0 is poor in terms of cost-effectiveness. In the future, we will compare surgical and conservative treatment groups to assess whether surgical interventions for adult spinal malformations are truly cost-effective. Seventh, a subanalysis focused on degenerative scoliosis was performed to match the patients' background in the Grade-2, three-column, and LLIF groups. However, the subanalysis of degenerative scoliosis did not completely match patient backgrounds in the three groups, and their comparison may have involved bias.

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