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Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis
Journal of Orthopaedic Science xxx (2018) 1e5
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Original Article
Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis Mitsuru Yagi a, b, d, Nobuyuki Fujita a, d, Eijiro Okada a, d, Osahiko Tsuji a, d, Narihito Nagoshi a, d, Takashi Tsuji c, d, Masaya Nakamura a, d, Morio Matsumoto a, d, Kota Watanabe a, d, * a
Department of Orthopedic Surgery, Keio University School of Medicine, Japan Department of Orthopedic Surgery, National Hospital Organization Murayama Medical Center, Japan c Department of Orthopedic Surgery, Fujita Health University, Japan d Keio Spine Research Group (KSRG), Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 November 2017 Received in revised form 23 March 2018 Accepted 3 April 2018 Available online xxx
Background: Cost-utility analysis of surgery for degenerative lumber spondylolisthesis (DS) is essential for healthcare providers and patients to select appropriate treatment. The purpose of this study was to review the cost-utility of decompression alone versus decompression with fusion for DS. Methods: A retrospective review of 99 consecutive patients who were treated for Meyerding grade 1 DS at two representative spine centers was performed. Patients with significant spinal instability were treated by decompression with fusion (F group, 40 patients); all others were treated by decompression surgery alone (D group, 59 patients). All patients were followed for three years. Demographic and radiographic data, health-related quality of life (HRQoL), and the direct cost for surgery were analyzed, and the incremental cost-effectiveness ratio (ICER) was determined using cost/quality-adjusted life years (QALY). Results: There were no differences between the groups in baseline demographics (D vs. F: age 68 ± 9 vs. 66 ± 7 years; 37% vs. 40% female) or HRQoL (ODI: D, 41 ± 16 vs. F, 46 ± 13%). The F group had a higher initial-surgery cost ($18,992 ± 2932) but lower reoperation frequency (7%) than the D group ($7660 ± 2182 and 12%, respectively). The three-year total direct cost was higher for F than for D ($19,222 ± 3332 vs. $9668 ± 6,168, p ¼ .01). ICER was higher for F at one year ($136,408 ± 187,911 vs. $237,844 ± 212,049, p < .01), but was comparable for F and D at three years (D, $41,923 ± 44,503 vs. F, $51,313 ± 32,849, p ¼ .17). Conclusion: At the three-year follow-up, the two methods had comparable cost-utility. Both methods were cost-effective (defined as an ICER within three times the per-capita gross domestic product). © 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
1. Introduction Cost-utility analysis (CUA) of surgical procedures for degenerative spinal conditions is critical for both patients and healthcare providers. As the population ages, the percentage affected by degenerative spinal conditions is growing, and more patients are expected to present with painful spinal conditions requiring
* Corresponding author. 35 Shinanomachi, Shinjyuku, Tokyo, Japan. Fax: þ81 3.3353.1232. E-mail address: [email protected] (K. Watanabe).
surgery in the coming years [1,2]. Therefore, there is an urgent need to conduct economic evaluation of elective surgery for degenerative spinal conditions using standardized methods and transparent reporting [1]. Degenerative lumbar spondylolisthesis (DS) is one of the most common degenerative spine conditions [3,4]. Enyo et al. reported that the prevalence of DS was 10% in their community based study (age 40e75 years) and the incidence of de novo DS was 13.9% during 15-year follow-up [4]. While the choice of conservative or surgical treatment depends on the type and severity of the patient's symptoms and the potential risks of surgical intervention [3],
https://doi.org/10.1016/j.jos.2018.04.001 0949-2658/© 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
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M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
recent randomized trials show that surgery is more effective for DS than conservative treatment when the appropriate surgical technique is selected for particular patients [5,6]. The primary surgical options are decompression surgery alone (D) and decompression with fusion (F) [1,3e7]. Two recent randomized controlled trials (RCTs) comparing the effectiveness of D and F for lumbar spinal stenosis with or without DS reported that both procedures can significantly improve health-related quality of life (HRQoL) measured at the three-year and five-year follow-up [8,9]. Elective spine surgeries for DS have favorable clinical outcomes but also carry substantial risk for complications such as surgical-site infection, hematoma, paralysis, and pathologies at the same or adjacent level [7,10e13]. These complications often require extended hospitalization and multiple revision surgeries, subsequently increasing the direct cost of treatment. This study compared the direct costs and cost-utility between groups treated by D or F for lumbar spinal stenosis with DS.
the hospital but did not include hospital overhead. Surgeons, anesthesiologists, and other physicians were included in the direct costs since they are paid by the healthcare system. Operating-room costs included all direct costs incurred during the operation, most of which were for implants. Examination costs included radiographs, computed tomography scans, magnetic resonance imaging, and electromyography. Hospital costs included preoperative and postoperative epidural steroid injections, back-specific medications (nonsteroidal anti-inflammatory drugs, Cox-2 inhibitors, oral steroids, narcotics, muscle relaxants, and antidepressants), physical therapy, brace, food, room costs, and so forth. 2.4. Clinical outcomes Patient outcomes were evaluated based on the HRQoL using the Oswestry Disability Index (ODI). The baseline ODI and the postoperative ODI at one, two, and three years after the operation were determined.
2. Materials and methods 2.1. Patient population This study was approved from the IRB of each hospital. This study used a prospective database from two comprehensive spine centers to analyze data for 99 consecutive patients who were treated for DS, either by single-level decompression alone (laminotomy) or decompression with fusion (posterior lumbar interbody fusion [PLIF] or trans-foraminal lumbar interbody fusion), between April 2012 and April 2014. Both spine centers are representative state-of-the-art centers for treating spinal disorders, and all operations were performed by senior spinal surgeons. All data were collected prospectively and analyzed retrospectively. 2.2. Inclusion and exclusion criteria This study included adult patients (age 20 years) diagnosed with Meyerding grade 1 degenerative spondylolisthesis, defined by a 0e25% overhang of the vertebral body relative to the anteroposterior length of the body of the caudal vertebra in a lateral lumbar radiograph [8,9]. Patients with an end-plate angular change of more than 10 in flexion/extension radiographs were considered to have significant instability and were therefore treated by decompression with fusion. Patients were excluded if they were followed less than three years after surgery or had a previous spinal surgery. All patients were given antibiotics before and after the operation, and a drain was used for all patients. No patients received bone morphogenetic protein 2 or any other bone-growth stimulant. Of 66 candidates treated by D and 46 treated by F, those with complete radiographic, demographic, and HRQoL data were enrolled in the study, for a final population of 59 patients in the D group and 40 in the F group.
2.5. Cost-utility analysis The incremental cost-effectiveness ratio (ICER) was determined using cost/quality-adjusted life years (QALYs) [14,15], calculated from the three-year total hospitalization cost and the ODI. Based on a previously reported regression model, we calculated QALYs by converting ODI scores to Short-Form Health Survey (SF-6D) scores [16], setting the SF-6D equal to 0.782750.00518 ODI. 2.6. Statistical analysis Descriptive statistics were used to summarize collected data. Changes in HRQoL scores were evaluated by paired t-test. Differences between groups were analyzed by ManneWhitney U test and chi-squared analysis where appropriate. P-values <.05 were considered statistically significant. Data were analyzed using SPSS Statistics version 21.0 (IBM Corp., Armonk, NY). 3. Results 3.1. Baseline demographic data and radiographic comparisons As shown in Table 1, there were no significant differences between the D and F groups in age, gender, baseline HRQoL, occupation, or history of DM or smoking. Baseline radiographs showed that the percent slip was not different among D and F group whereas end-plate angular change in flexion/extension radiograph was significantly large in F group when compared with D group (D
Table 1 Baseline demographics and radiographics of the study population.
2.3. Data collection and radiographic assessment Collected demographic and clinical data included patient age, gender, occupation, history of diabetes mellitus (DM), history of smoking, and length of hospital stay. All costs were recorded according to resource use, derived from institutional records. Hospital discharge and billing records for all subjects were collected in a prospective longitudinal registry. All billable procedures from the index hospitalization and all hospitalizations related to the operation during the three-year follow-up period were recorded prospectively. Direct hospital costs incurred for the operation and any readmission-related costs were collected from hospital administrative data. These costs included all direct supply costs incurred by
No. of patients Age (years) Gender (female: male, %) Diabetes mellitus (%) Smoker (%) Occupation (%) White-collar job Blue-collar job Unemployed (housewife) Unemployed (others) %slip (%) End-plate angular change ( )
D group
F group
P-value
59 68.5 ± 9.3 22: 37 (37: 63%) 5 (9%) 10 (17%)
40 66.7 ± 7.1 16: 24 (40: 60%) 6 (15%) 6 (15%)
0.43 0.78 0.31 0.79
22 (38%) 16 (27%) 14 (24%) 5 (8%) 9.3 ± 5.9 3.9 ± 3.3
16 (39%) 10 (24%) 11 (27%) 3 (8%) 11.3 ± 3.6 10.9 ± 3.4
0.22
0.33 0.01a
Means and standard deviations (percentage in parentheses). a Statistically significant.
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
group; %slip: 9.3 ± 5.9%, and end-plate angular change: 3.9 ± 3.3 , F group; %slip: 11.3 ± 3.6%, and end-plate angular change:10.9 ± 3.4 , p ¼ .33 and p < .01, respectively).
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4. Discussion
The projected cost/QALY decreased over the three-year followup period, from $136,408 ± 187,911 to $41,923 ± 44,503 in the D group, and from $237,844 ± 212,049 to $51,313 ± 32,849 in the F group. The cost/QALY was significantly higher in the F group one year after surgery, but there was no difference in cost/QALY between the groups at two and three years after surgery (Table 5).
Escalating medical costs make it critical to optimize costs and outcomes, especially for surgical procedures to treat degenerative conditions [17e19]. Here, we analyzed the one-, two-, and threeyear cost and cost-utility of two representative surgical treatments for 99 patients with DS. The World Health Organization (WHO) considers cost-utility analysis (CUA) to be best suited for comparing two drugs or procedures that may have different benefits [20]. CUA is used to determine cost in terms of utility, especially in the quantity and quality of life (QoL). CUA reveals the value for money in terms of a single type of health outcome, and in this case the ICER is usually expressed as the incremental cost for a net gain of QALY. This approach incorporates both increases in survival time and changes in QoL into one measure, making comparisons across different types of health outcome relatively easy. In the present study, the mean one-year cost/QALY was $136,408 ± 187,911 in the D group and $237,844 ± 212,049 in the F group, with a mean QALY improvement of 0.13 ± 0.09 in the D group and 0.14 ± 0.08 in the F group. Although surgery significantly improved the HRQoL for DS those who had spinal instability, the one-year postoperative cost/QALY exceeded the upper threshold for cost-effectiveness set by WHO (three times the per-capita GDP, which is ~$90,000 in our nation) [17,18]. However, the mean threeyear cost/QALY was $41,923 ± 44,503 in the D group and $51,313 ± 32,849 in the F group, with a mean cumulative QALY improvement of 0.39 ± 0.24 in the D group and 0.48 ± 0.20 in the F group. For both groups, the total direct cost at three years after surgery was within three times the per-capita GDP, and was therefore considered cost-effective. Comparison of the D and F cost and cost-utility revealed that the cost/QALY at one year after surgery was significantly higher in the F than the D group; however, at three years, there was no difference in cumulative cost/QALY between the two groups despite the difference of surgical indication. Losina et al. reviewed the cost/QALY of total joint replacement, which is a costly type of orthopedic surgery, and reported that the mean lifetime cost/QALY was $18,300 [21]. They concluded that both total hip replacement (THA) and total knee replacement (TKA) are highly cost-effective, based on a number of high-quality studies. Rampersaud et al. also reviewed the 5-year cost/QALY of total joint replacement and reported that the median 5-year cost/QALY was $21,702 for THA and $28,595 for TKA [22]. In the present study, we reviewed the 3-year cost-effectiveness of elective lumbar spine
Table 2 Comparisons of clinical outcomes.
Table 4 Cost comparisons for surgery for DS.
3.2. Preoperative and postoperative HRQoL As shown in Table 2, the baseline, one-year, and two-year ODI scores did not differ between the D and F groups. ODI scores were improved significantly in both groups (18.5 ± 9.5% in F group and 14.6 ± 7.8% in D group). The three-year cumulative QALY was 0.48 ± 0.20 in the F group and 0.39 ± 0.24 in the D group (Table 3). The mean hospital stay in the F group was 13.3 ± 4.4 days, which was significantly longer than that in the D group (10.6 ± 2.4 days; p ¼ .05). In the D group, seven patients (12%) were re-admitted for a spine-related procedure within three years after the operation, compared to three F-group patients (7%); the three-year postoperative revision rate was significantly higher in the D group (p ¼ .04).
3.3. Cost comparisons The total direct hospital costs for the initial operation averaged $7660 ± 2181 in the D group and $18,992 ± 2932 in the F group. As shown in Table 4, costs were significantly higher in the F group for both the surgery (p < .01) and for surgical implants (p < .01). Although the cost of hospitalization was comparable in the two groups (p ¼ .35), the mean length of hospital stay was significantly longer in the F group (p ¼ .05). The average total hospital cost per patient, including readmissions during the three-year follow-up period, was significantly higher for the F group than the D group (p ¼ .01; Table 4).
3.4. Cost-utility analysis
D group ODI ODI ODI ODI
(%, (%, (%, (%,
baseline) 1-year post-op) 2-year post-op) 3-year post-op)
41.0 19.8 19.1 18.5
± ± ± ±
F group
16.3 11.8 13.1 9.5
45.7 19.2 15.9 14.6
± ± ± ±
12.8 12.2 9.3 7.8
P-value 0.07 0.48 0.09 0.01a
Means and standard deviations. a Statistically significant.
Means and standard deviations. a Statistically significant.
7660 3273 2851 3311 9680
± ± ± ± ±
2181 1030 463 773 6168
F group
P-value
18,992 ± 2932 7953 ± 1564 6161 ± 662 4309 ± 933 19,222 ± 3332
<0.01a <0.01a <0.01a 0.16 <0.01a
Means and standard deviations. a Statistically significant.
Table 3 Cumulative QALY gains after surgery for DS.
QALY gain (1-year post-op) Cumulative QALY gain (2-year post-op) Cumulative QALY gain (3-year post-op)
D group Index surgery ($) Implant cost ($) Surgery cost ($) Hospital cost ($) 3-year total direct cost ($)
Table 5 Cost-utility comparisons of surgery for DS. D group
F group
P-value
0.13 ± 0.09 0.26 ± 0.16 0.39 ± 0.24
0.14 ± 0.08 0.31 ± 0.14 0.48 ± 0.20
0.34 0.06 0.01a
Cost/QALY at 1 year ($) Cost/QALY at 2 years ($) Cost/QALY at 3 years ($)
D group
F group
P-value
136,408 ± 187,911 66,121 ± 82,105 41,923 ± 44,503
237,844 ± 212,049 802,339 ± 51,739 51,313 ± 32,849
0.01a 0.26 0.17
Means and standard deviations. a Statistically significant.
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
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M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
surgery, and did not directly compare the results with those of joint replacement. However, based on the initial cost and 2-year HRQoL of the F group and on the reported data for joint replacement surgery, our results suggest that the cost-effectiveness of elective spine surgery for degenerative lumbar spondylolisthesis is comparable to that of joint replacement within 3 years after surgery. Posterolateral fusion (PLF) is one of the surgeries used to treat degenerative lumbar spondylolisthesis. In this study, we did not review the cost-effectiveness of PLF, because we did not perform it to treat this condition. The implant cost in PLF is generally lower than that of PLIF because it does not require interbody fusion with cages, so the cost-effectiveness of PLF could be better than that of PLIF. On the other hand, PLF is reported to be associated with a high pseudoarthrosis rate and frequent revision surgery [23]. Bydon et al. compared the cost-effectiveness of PLIF versus PLF in 137 patients with lumbar spondylolisthesis and concluded that PLIF was more cost-effective than PLF at the 3.5-year post-operation time point, because of the higher frequency of reoperation with PLF. Taken together, further study is needed to evaluate the costeffectiveness of PLF with respect to elective spine surgery for degenerative lumbar disorders [24]. 4.1. Reoperation frequencies The reoperation frequency within the three years after surgery was 12% in the D group and 7% in the F group. Five patients had recurrent spinal stenosis and received either PLIF or TLIF, one patient had both same level and adjacent level stenosis and received 2 level PLIF, and 1 patient developed post-operative hematoma and received evacuation in D group. On the other hand, 2 patients had adjacent segmental disease and one patient received TLIF and 1 patient received decompression alone. One patient had surgical site infection and received irrigation and debridement procedure in F group. Both groups had slightly better reoperation rates than previously reported for their respective procedures [3,4]. Ghogawara et al. reported a 15% frequency of reoperation within one year of D surgery for DS [10]. Blumenthal et al. reported a 37.5% reoperation frequency of D surgery for DS during a mean follow-up period of 3.6 years [12]. Deyo et al. reported a 10.6% incidence of reoperation after F for DS, and Kim et al. reported a 14.2% incidence of reoperation during a mean follow-up period of 3.5 years [11,13]. In the present study, the reoperation frequency was slightly higher in the D group (12%), resulting in an ~26% increase in total costs and a cost/QALY decrease of $728 compared to the F group. For each patient, the surgical method was selected after assessing the stability of the lumbar spine, and only patients with significant spinal instability were treated by F. Even so, the reoperation frequency was still slightly higher in the D than the F group. Significant risk factors identified for reoperation after D for DS include spinal instability, youth, being male, and preserved intervertebral disc height [5e13]. Sato et al. have previously described the incidence and independent risk factors for reoperation within five years after D or F in 163 consecutive DS patients [7], and found a cumulative reoperation rate of 10% at one year and 24% at three years after D, and 2% at one year and 8% at three years after F. Compared to our previous report, the frequency of reoperation within three years of surgery was lower for both groups in the present study, which might indicate an improvement in selecting the procedure for individual patients. Medical history can also affect the postoperative HRQoL. For instance, 9% of the D-group and 15% of the F-group patients had a history of DM; of these, one patient in each group had a surgicalsite infection requiring irrigation and debridement. Surgical-site infections are more frequent in patients with DM [25,26]. Additionally, 17% of the D-group and 15% of the F-group patients were
smokers. Several factors affect the success of spinal fusion, including age, DM, osteoporosis, and smoking [4,11,26,27], and the negative impact of smoking on bone fusion after lumbar-fusion surgery is well documented [11,27e29]. A recent study reported a clinically significant deterioration in HRQoL after elective spine surgery in patients who smoke. Thus, adequate preoperative treatment of both smoking habits and DM might reduce the risk of surgical-site infection and pseudoarthrosis thereby improving the postoperative HRQoL and the cost-utility for each method. 4.2. Superior HRQoL improvement in the F group In the present study, the three-year postoperative HRQoL was significantly better in the F than the D group, despite comparable baseline demographic data (i.e., gender distribution, mean age, smoking history, history of DM, HRQoL scores, and type of occupation). The three-year cumulative QALY was also significantly better in the F group, and the three-year ICER was comparable in the F and D groups despite the high three-year cumulative total cost in the F group. However, we cannot conclude that F is superior to D when treating DS, because of the difference of surgical indication. We chose F for only those with significant spinal instability and chose D for those without spinal instability. Several reports have demonstrated superior postoperative outcomes for F compared to D [5,10e12]. However, there is presently no consensus as to the superiority of either procedure for treating DS. In two recent RCTs comparing the effectiveness of D versus F for lumbar spinal stenosis with or without DS, both procedures significantly improved the HRQoL. However, the studies differed as to the effectiveness of the two methods. Ghogawara et al. found €rsth et al. that F improved the HRQoL slightly more than D [8], but Fo found that F did not improve the two-year or five-year clinical outcomes compared to D [9]. Both RCTs demonstrated that in most cases, stenosis surgery should be limited to D if there is no overt instability [8,9]. Surgical procedures in the present study were selected in accordance with the results of these RCTs, and improved surgical selection may have reduced the reoperations rates and improved the ICER for both methods. 4.3. Spinal implant costs in the F group Spinal-implant costs, which included the cost of sutures and bone substitute as well as spinal implants, were significantly higher in the F group. The average implant costs in the F group ($7953 ± 1564 for the initial surgery) increased the total cost in the F group by ~42% and the ICER by ~23%. Our study has some limitations. First, the study population was small and heterogeneous, which made it difficult to draw strong conclusions about the outcomes of DS surgery based on cost utility analysis results. DS patients cannot be generally categorized as to gender, age, occupation, or comorbidities, and exhibit various degrees of spinal instability [5,6]. DS causes severe disability in some patients and mild symptoms in others [5,6]. In the present study, the patients were treated by D unless there was significant instability of the spine, in which case they were treated by F. Given this selection bias, our results may not be universally representative of DS treatment. However, our experience is that neither method, D or F, can be considered universally optimal for all patients with DS. Rather, accurate selection of the appropriate surgery for each patient is key in obtaining better clinical outcomes for both methods when treating DS. Second, the 3-year post-operative follow-up term in this study was relatively short for evaluating the costeffectiveness of elective spine surgery. Previous reports describe a high revision rate for decompression and fusion surgery due to an increase in adjacent segmental disease at middle to long time
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
periods after the operation. Therefore, the re-examination of this patient cohort at later follow-up times may provide further information about the cost-effectiveness of elective spine surgery [7]. In addition, healthcare systems vary in different countries. The national health insurance system is available in Japan, so the patient payment is consistent for high-cost treatments [17,18]. Thus, it can be assumed that there is no bias in choosing a treatment based on patient income and insurance type. However, due to the variability in healthcare systems throughout the world, caution is needed when interpretating these results for other countries. In the present study, the one-year cost/QALY exceeded the costeffective threshold in both groups. The high initial cost of orthopedic surgery highlights the importance of long follow-up periods and accurate HRQoL assessment when evaluating the cost-utility of elective spinal surgery for DS. Additionally, lower revision rates and better clinical outcomes were indispensable for improving ICERs. Thus, it is important for physicians to select the appropriate procedure for each patient and to weigh the surgical risks to avoid major complications that would require additional surgery. In this study, both methods, D and F, for treating DS were cost-effective when the technique was selected appropriately for the patient. 5. Conclusion The cost-utility of elective spine surgery for DS over a three-year postoperative period did not differ significantly between D and F. For both methods, the three-year ICER was within three times the percapita GDP for surgery. Therefore, both methods are cost-effective for the surgical treatment of DS. Further large-sample studies with long-term follow-up periods or simulation-based studies will further clarify the cost-utility of surgical treatments for DS. Conflict of interest The authors declare that they have no conflict of interest. References [1] Brauer CA, Rosen AB, Olchanski NV, Neumann PJ. Cost-utility analyses in orthopaedic surgery. J Bone Jt Surg Am. 2005 Jun;87(6):1253e9. [2] Martin CR, Gruszczynski AT, Braunsfurth HA, Fallatah SM, O'Neil J, Wai EK. The surgical management of degenerative lumbar spondylolisthesis: a systematic review. Spine (Phila Pa 1976) 2007 Jul;32(16):1791e8. [3] Ghogawala Z, Resnick DK, Glassman SD, Dziura J, Shaffrey CI, Mummaneni PV. Randomized controlled trials for degenerative lumbar spondylolisthesis: which patients benefit from lumbar fusion? J Neurosurg Spine 2017 Feb;26(2):260e6. [4] Enyo Y, Yoshimura N, Yamada H, Hashizume H, Yoshida M. Radiographic natural course of lumbar degenerative spondylolisthesis and its risk factors related to the progression and onset in a 15-year community-based cohort study: the Miyama study. J Orthop Sci 2015 Nov;20(6):978e84. [5] Pearson A, Blood E, Lurie J, Tosteson T, Abdu WA, Hillibrand A, Bridwell K, Weinstein J. Degenerative spondylolisthesis versus spinal stenosis: does a slip matter? Comparison of baseline characteristics and outcomes (SPORT). Spine 2010 Feb;35(3):298e305. [6] Weinstein JN, Tosteson TD, Lurie JD, Tosteson AN, Blood E, Hanscom B, Herkowitz H, Cammisa F, Albert T, Boden SD, Hilibrand A, Goldberg H, Berven S, An H. SPORT Investigators. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med 2008 Feb;358(8):794e810. [7] Sato S, Yagi M, Machida M, Yasuda A, Konomi T, Miyake A, Fujiyoshi K, Kaneko S, Takemitsu M, Machida M, Yato Y, Asazuma T. Revision rate and risk factors of elective spinal surgery for degenerative spondylolisthesis: minimum 5-year follow-up. Spine J 2015 Jul;15(7):1536e44.
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[8] Ghogawala Z, Dziura J, Butler WE, Dai F, Terrin N, Magge SN, Coumans JV, Harrington JF, Amin-Hanjani S, Schwartz JS, Sonntag VK, Barker 2nd FG, Benzel EC. Laminectomy plus fusion versus laminectomy alone for lumbar spondylolisthesis. N Engl J Med 2016 Apr;374(15):1424e34. € €rsth P, Olafsson €m F, Fritzell P, Ohagen [9] Fo G, Carlsson T, Frost A, Borgstro P, €lsson K, Sande n B. A randomized, controlled trial of fusion surgery for Michae lumbar spinal stenosis. N Engl J Med 2016 Apr;374(15):1413e23. [10] Blumenthal C, Curran J, Benzel EC, Potter R, Magge SN, Harrington Jr JF, Coumans JV, Ghogawala Z. Radiographic predictors of delayed instability following decompression without fusion for degenerative grade I lumbar spondylolisthesis. J Neurosurg Spine 2013 Apr;18(4):340e6. [11] Deyo RA, Martin BI, Kreuter W, Jarvik JG, Angier H, Mirza SK. Revision surgery following operations for lumbar stenosis. J Bone Jt Surg Am. 2011 Nov;93(21): 1979e86. [12] Ghogawala Z, Benzel EC, Amin-Hanjani S, Barker 2nd FG, Harrington JF, Magge SN, Strugar J, Coumans JV, Borges LF. Prospective outcomes evaluation after decompression with or without instrumented fusion for lumbar stenosis and degenerative Grade I spondylolisthesis. J Neurosurg Spine 2004 Oct;1(3): 267e72. [13] Kim CH, Chung CK, Park CS, Choi B, Hahn S, Kim MJ, Lee KS, Park BJ. Reoperation rate after surgery for lumbar spinal stenosis without spondylolisthesis: a nationwide cohort study. Spine J 2013 Oct;13(10):1230e7. [14] Weinstein MC, Torrance G, McGuire A. QALYs: the basics. Value Health 2009 Mar;12(Suppl. 1):S5e9. Erratum in: Value Health. 2010;13(8):1065. [15] Hirth RA, Chernew ME, Miller E, Fendrick AM, Weissert WG. Willingness to pay for a quality-adjusted life year: in search of a standard. Med Decis Making 2000 Jul-Sep;20(3):332e42. [16] Carreon LY, Glassman SD, McDonough CM, Rampersaud R, Berven S, Shainline M. Predicting SF-6D utility scores from the Oswestry disability index and numeric rating scales for back and leg pain. Spine (Phila Pa 1976) 2009 Sep;34(19):2085e9. [17] World Health Organization. The world health report 2000-health systems: improving performance. 2000. [18] World Health Organization. Health service delivery Profiles-Japan. 2012. [19] Ministry of Health, Labour, and Welfare. National health expenditures summary (Report). 2010-09-27 [in Japanese]. [20] Edejer TT, Baltussen R, Adam T, Hutubessy R, Acharya A, Evans DB, Murray CJL. WHO guide to cost-effectiveness analysis. Geneva: World Health Organization; 2003. [21] Losina E, Walensky RP, Kessler CL, Emrani PS, Reichmann WM, Wright EA, Holt HL, Solomon DH, Yelin E, Paltiel AD, Katz JN. Cost-effectiveness of total knee arthroplasty in the United States: patient risk and hospital volume. Arch Intern Med 2009 Jun 22;169(12):1113e21. [22] Rampersaud YR, Tso P, Walker KR, Lewis SJ, Davey JR, Mahomed NN, Coyte PC. Comparative outcomes and cost-utility following surgical treatment of focal lumbar spinal stenosis compared with osteoarthritis of the hip or knee: part 2eestimated lifetime incremental cost-utility ratios. Spine J 2014 Feb 1;14(2):244e54. [23] Mummaneni PV, Dhall SS, Eck JC, Groff MW, Ghogawala Z, Watters 3rd WC, Dailey AT, Resnick DK, Choudhri TF, Sharan A, Wang JC, Kaiser MG. Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 11: interbody techniques for lumbar fusion. J Neurosurg Spine 2014 Jul;21(1):67e74. [24] Bydon M, Macki M, Abt NB, Witham TF, Wolinsky JP, Gokaslan ZL, Bydon A, Sciubba DM. The cost-effectiveness of interbody fusions versus posterolateral fusions in 137 patients with lumbar spondylolisthesis. Spine J 2015 Mar 1;15(3):492e8. [25] Ishii M, Iwasaki M, Ohwada T, Oda T, Matsuoka T, Tamura Y, Izawa K. Postoperative deep surgical-site infection after instrumented spinal surgery: a multicenter study. Global Spine J 2013 Jun;3(2):95e102. [26] Pull ter Gunne AF, Mohamed AS, Skolasky RL, Skolasky RL, van Laarhoven CJ, Cohen DB. The presentation, incidence, etiology, and treatment of surgical site infections after spinal surgery. Spine (Phila Pa 1976) 2010 Jun;35(13):1323e8. [27] Adogwa O, Elsamadicy AA, Han J, Karikari IO, Cheng J, Bagley CA. Drivers of 30-day Re-admission in elderly patients (>65 Years old) after spine surgery: an analysis of 500 consecutive spine surgery patients. World Neurosurg 2017 Jan;97:518e22. https://doi.org/10.1016/j.wneu.2016.07.032 [Epub 2016 Jul 27]. [28] Jackson 2nd KL, Devine JG. The effects of smoking and smoking cessation on spine surgery: a systematic review of the literature. Global Spine J 2016 Nov;6(7):695e701. [29] Nerland US, Jakola AS, Giannadakis C, Solheim O, Weber C, Nygaard ØP, Solberg TK, Gulati S. The risk of getting worse: predictors of deterioration after decompressive surgery for lumbar spinal stenosis: a multicenter observational study. World Neurosurg 2015 Oct;84(4):1095e102.
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Original Article
Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis Mitsuru Yagi a, b, d, Nobuyuki Fujita a, d, Eijiro Okada a, d, Osahiko Tsuji a, d, Narihito Nagoshi a, d, Takashi Tsuji c, d, Masaya Nakamura a, d, Morio Matsumoto a, d, Kota Watanabe a, d, * a
Department of Orthopedic Surgery, Keio University School of Medicine, Japan Department of Orthopedic Surgery, National Hospital Organization Murayama Medical Center, Japan c Department of Orthopedic Surgery, Fujita Health University, Japan d Keio Spine Research Group (KSRG), Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 November 2017 Received in revised form 23 March 2018 Accepted 3 April 2018 Available online xxx
Background: Cost-utility analysis of surgery for degenerative lumber spondylolisthesis (DS) is essential for healthcare providers and patients to select appropriate treatment. The purpose of this study was to review the cost-utility of decompression alone versus decompression with fusion for DS. Methods: A retrospective review of 99 consecutive patients who were treated for Meyerding grade 1 DS at two representative spine centers was performed. Patients with significant spinal instability were treated by decompression with fusion (F group, 40 patients); all others were treated by decompression surgery alone (D group, 59 patients). All patients were followed for three years. Demographic and radiographic data, health-related quality of life (HRQoL), and the direct cost for surgery were analyzed, and the incremental cost-effectiveness ratio (ICER) was determined using cost/quality-adjusted life years (QALY). Results: There were no differences between the groups in baseline demographics (D vs. F: age 68 ± 9 vs. 66 ± 7 years; 37% vs. 40% female) or HRQoL (ODI: D, 41 ± 16 vs. F, 46 ± 13%). The F group had a higher initial-surgery cost ($18,992 ± 2932) but lower reoperation frequency (7%) than the D group ($7660 ± 2182 and 12%, respectively). The three-year total direct cost was higher for F than for D ($19,222 ± 3332 vs. $9668 ± 6,168, p ¼ .01). ICER was higher for F at one year ($136,408 ± 187,911 vs. $237,844 ± 212,049, p < .01), but was comparable for F and D at three years (D, $41,923 ± 44,503 vs. F, $51,313 ± 32,849, p ¼ .17). Conclusion: At the three-year follow-up, the two methods had comparable cost-utility. Both methods were cost-effective (defined as an ICER within three times the per-capita gross domestic product). © 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
1. Introduction Cost-utility analysis (CUA) of surgical procedures for degenerative spinal conditions is critical for both patients and healthcare providers. As the population ages, the percentage affected by degenerative spinal conditions is growing, and more patients are expected to present with painful spinal conditions requiring
* Corresponding author. 35 Shinanomachi, Shinjyuku, Tokyo, Japan. Fax: þ81 3.3353.1232. E-mail address: [email protected] (K. Watanabe).
surgery in the coming years [1,2]. Therefore, there is an urgent need to conduct economic evaluation of elective surgery for degenerative spinal conditions using standardized methods and transparent reporting [1]. Degenerative lumbar spondylolisthesis (DS) is one of the most common degenerative spine conditions [3,4]. Enyo et al. reported that the prevalence of DS was 10% in their community based study (age 40e75 years) and the incidence of de novo DS was 13.9% during 15-year follow-up [4]. While the choice of conservative or surgical treatment depends on the type and severity of the patient's symptoms and the potential risks of surgical intervention [3],
https://doi.org/10.1016/j.jos.2018.04.001 0949-2658/© 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
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M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
recent randomized trials show that surgery is more effective for DS than conservative treatment when the appropriate surgical technique is selected for particular patients [5,6]. The primary surgical options are decompression surgery alone (D) and decompression with fusion (F) [1,3e7]. Two recent randomized controlled trials (RCTs) comparing the effectiveness of D and F for lumbar spinal stenosis with or without DS reported that both procedures can significantly improve health-related quality of life (HRQoL) measured at the three-year and five-year follow-up [8,9]. Elective spine surgeries for DS have favorable clinical outcomes but also carry substantial risk for complications such as surgical-site infection, hematoma, paralysis, and pathologies at the same or adjacent level [7,10e13]. These complications often require extended hospitalization and multiple revision surgeries, subsequently increasing the direct cost of treatment. This study compared the direct costs and cost-utility between groups treated by D or F for lumbar spinal stenosis with DS.
the hospital but did not include hospital overhead. Surgeons, anesthesiologists, and other physicians were included in the direct costs since they are paid by the healthcare system. Operating-room costs included all direct costs incurred during the operation, most of which were for implants. Examination costs included radiographs, computed tomography scans, magnetic resonance imaging, and electromyography. Hospital costs included preoperative and postoperative epidural steroid injections, back-specific medications (nonsteroidal anti-inflammatory drugs, Cox-2 inhibitors, oral steroids, narcotics, muscle relaxants, and antidepressants), physical therapy, brace, food, room costs, and so forth. 2.4. Clinical outcomes Patient outcomes were evaluated based on the HRQoL using the Oswestry Disability Index (ODI). The baseline ODI and the postoperative ODI at one, two, and three years after the operation were determined.
2. Materials and methods 2.1. Patient population This study was approved from the IRB of each hospital. This study used a prospective database from two comprehensive spine centers to analyze data for 99 consecutive patients who were treated for DS, either by single-level decompression alone (laminotomy) or decompression with fusion (posterior lumbar interbody fusion [PLIF] or trans-foraminal lumbar interbody fusion), between April 2012 and April 2014. Both spine centers are representative state-of-the-art centers for treating spinal disorders, and all operations were performed by senior spinal surgeons. All data were collected prospectively and analyzed retrospectively. 2.2. Inclusion and exclusion criteria This study included adult patients (age 20 years) diagnosed with Meyerding grade 1 degenerative spondylolisthesis, defined by a 0e25% overhang of the vertebral body relative to the anteroposterior length of the body of the caudal vertebra in a lateral lumbar radiograph [8,9]. Patients with an end-plate angular change of more than 10 in flexion/extension radiographs were considered to have significant instability and were therefore treated by decompression with fusion. Patients were excluded if they were followed less than three years after surgery or had a previous spinal surgery. All patients were given antibiotics before and after the operation, and a drain was used for all patients. No patients received bone morphogenetic protein 2 or any other bone-growth stimulant. Of 66 candidates treated by D and 46 treated by F, those with complete radiographic, demographic, and HRQoL data were enrolled in the study, for a final population of 59 patients in the D group and 40 in the F group.
2.5. Cost-utility analysis The incremental cost-effectiveness ratio (ICER) was determined using cost/quality-adjusted life years (QALYs) [14,15], calculated from the three-year total hospitalization cost and the ODI. Based on a previously reported regression model, we calculated QALYs by converting ODI scores to Short-Form Health Survey (SF-6D) scores [16], setting the SF-6D equal to 0.782750.00518 ODI. 2.6. Statistical analysis Descriptive statistics were used to summarize collected data. Changes in HRQoL scores were evaluated by paired t-test. Differences between groups were analyzed by ManneWhitney U test and chi-squared analysis where appropriate. P-values <.05 were considered statistically significant. Data were analyzed using SPSS Statistics version 21.0 (IBM Corp., Armonk, NY). 3. Results 3.1. Baseline demographic data and radiographic comparisons As shown in Table 1, there were no significant differences between the D and F groups in age, gender, baseline HRQoL, occupation, or history of DM or smoking. Baseline radiographs showed that the percent slip was not different among D and F group whereas end-plate angular change in flexion/extension radiograph was significantly large in F group when compared with D group (D
Table 1 Baseline demographics and radiographics of the study population.
2.3. Data collection and radiographic assessment Collected demographic and clinical data included patient age, gender, occupation, history of diabetes mellitus (DM), history of smoking, and length of hospital stay. All costs were recorded according to resource use, derived from institutional records. Hospital discharge and billing records for all subjects were collected in a prospective longitudinal registry. All billable procedures from the index hospitalization and all hospitalizations related to the operation during the three-year follow-up period were recorded prospectively. Direct hospital costs incurred for the operation and any readmission-related costs were collected from hospital administrative data. These costs included all direct supply costs incurred by
No. of patients Age (years) Gender (female: male, %) Diabetes mellitus (%) Smoker (%) Occupation (%) White-collar job Blue-collar job Unemployed (housewife) Unemployed (others) %slip (%) End-plate angular change ( )
D group
F group
P-value
59 68.5 ± 9.3 22: 37 (37: 63%) 5 (9%) 10 (17%)
40 66.7 ± 7.1 16: 24 (40: 60%) 6 (15%) 6 (15%)
0.43 0.78 0.31 0.79
22 (38%) 16 (27%) 14 (24%) 5 (8%) 9.3 ± 5.9 3.9 ± 3.3
16 (39%) 10 (24%) 11 (27%) 3 (8%) 11.3 ± 3.6 10.9 ± 3.4
0.22
0.33 0.01a
Means and standard deviations (percentage in parentheses). a Statistically significant.
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
group; %slip: 9.3 ± 5.9%, and end-plate angular change: 3.9 ± 3.3 , F group; %slip: 11.3 ± 3.6%, and end-plate angular change:10.9 ± 3.4 , p ¼ .33 and p < .01, respectively).
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4. Discussion
The projected cost/QALY decreased over the three-year followup period, from $136,408 ± 187,911 to $41,923 ± 44,503 in the D group, and from $237,844 ± 212,049 to $51,313 ± 32,849 in the F group. The cost/QALY was significantly higher in the F group one year after surgery, but there was no difference in cost/QALY between the groups at two and three years after surgery (Table 5).
Escalating medical costs make it critical to optimize costs and outcomes, especially for surgical procedures to treat degenerative conditions [17e19]. Here, we analyzed the one-, two-, and threeyear cost and cost-utility of two representative surgical treatments for 99 patients with DS. The World Health Organization (WHO) considers cost-utility analysis (CUA) to be best suited for comparing two drugs or procedures that may have different benefits [20]. CUA is used to determine cost in terms of utility, especially in the quantity and quality of life (QoL). CUA reveals the value for money in terms of a single type of health outcome, and in this case the ICER is usually expressed as the incremental cost for a net gain of QALY. This approach incorporates both increases in survival time and changes in QoL into one measure, making comparisons across different types of health outcome relatively easy. In the present study, the mean one-year cost/QALY was $136,408 ± 187,911 in the D group and $237,844 ± 212,049 in the F group, with a mean QALY improvement of 0.13 ± 0.09 in the D group and 0.14 ± 0.08 in the F group. Although surgery significantly improved the HRQoL for DS those who had spinal instability, the one-year postoperative cost/QALY exceeded the upper threshold for cost-effectiveness set by WHO (three times the per-capita GDP, which is ~$90,000 in our nation) [17,18]. However, the mean threeyear cost/QALY was $41,923 ± 44,503 in the D group and $51,313 ± 32,849 in the F group, with a mean cumulative QALY improvement of 0.39 ± 0.24 in the D group and 0.48 ± 0.20 in the F group. For both groups, the total direct cost at three years after surgery was within three times the per-capita GDP, and was therefore considered cost-effective. Comparison of the D and F cost and cost-utility revealed that the cost/QALY at one year after surgery was significantly higher in the F than the D group; however, at three years, there was no difference in cumulative cost/QALY between the two groups despite the difference of surgical indication. Losina et al. reviewed the cost/QALY of total joint replacement, which is a costly type of orthopedic surgery, and reported that the mean lifetime cost/QALY was $18,300 [21]. They concluded that both total hip replacement (THA) and total knee replacement (TKA) are highly cost-effective, based on a number of high-quality studies. Rampersaud et al. also reviewed the 5-year cost/QALY of total joint replacement and reported that the median 5-year cost/QALY was $21,702 for THA and $28,595 for TKA [22]. In the present study, we reviewed the 3-year cost-effectiveness of elective lumbar spine
Table 2 Comparisons of clinical outcomes.
Table 4 Cost comparisons for surgery for DS.
3.2. Preoperative and postoperative HRQoL As shown in Table 2, the baseline, one-year, and two-year ODI scores did not differ between the D and F groups. ODI scores were improved significantly in both groups (18.5 ± 9.5% in F group and 14.6 ± 7.8% in D group). The three-year cumulative QALY was 0.48 ± 0.20 in the F group and 0.39 ± 0.24 in the D group (Table 3). The mean hospital stay in the F group was 13.3 ± 4.4 days, which was significantly longer than that in the D group (10.6 ± 2.4 days; p ¼ .05). In the D group, seven patients (12%) were re-admitted for a spine-related procedure within three years after the operation, compared to three F-group patients (7%); the three-year postoperative revision rate was significantly higher in the D group (p ¼ .04).
3.3. Cost comparisons The total direct hospital costs for the initial operation averaged $7660 ± 2181 in the D group and $18,992 ± 2932 in the F group. As shown in Table 4, costs were significantly higher in the F group for both the surgery (p < .01) and for surgical implants (p < .01). Although the cost of hospitalization was comparable in the two groups (p ¼ .35), the mean length of hospital stay was significantly longer in the F group (p ¼ .05). The average total hospital cost per patient, including readmissions during the three-year follow-up period, was significantly higher for the F group than the D group (p ¼ .01; Table 4).
3.4. Cost-utility analysis
D group ODI ODI ODI ODI
(%, (%, (%, (%,
baseline) 1-year post-op) 2-year post-op) 3-year post-op)
41.0 19.8 19.1 18.5
± ± ± ±
F group
16.3 11.8 13.1 9.5
45.7 19.2 15.9 14.6
± ± ± ±
12.8 12.2 9.3 7.8
P-value 0.07 0.48 0.09 0.01a
Means and standard deviations. a Statistically significant.
Means and standard deviations. a Statistically significant.
7660 3273 2851 3311 9680
± ± ± ± ±
2181 1030 463 773 6168
F group
P-value
18,992 ± 2932 7953 ± 1564 6161 ± 662 4309 ± 933 19,222 ± 3332
<0.01a <0.01a <0.01a 0.16 <0.01a
Means and standard deviations. a Statistically significant.
Table 3 Cumulative QALY gains after surgery for DS.
QALY gain (1-year post-op) Cumulative QALY gain (2-year post-op) Cumulative QALY gain (3-year post-op)
D group Index surgery ($) Implant cost ($) Surgery cost ($) Hospital cost ($) 3-year total direct cost ($)
Table 5 Cost-utility comparisons of surgery for DS. D group
F group
P-value
0.13 ± 0.09 0.26 ± 0.16 0.39 ± 0.24
0.14 ± 0.08 0.31 ± 0.14 0.48 ± 0.20
0.34 0.06 0.01a
Cost/QALY at 1 year ($) Cost/QALY at 2 years ($) Cost/QALY at 3 years ($)
D group
F group
P-value
136,408 ± 187,911 66,121 ± 82,105 41,923 ± 44,503
237,844 ± 212,049 802,339 ± 51,739 51,313 ± 32,849
0.01a 0.26 0.17
Means and standard deviations. a Statistically significant.
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
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surgery, and did not directly compare the results with those of joint replacement. However, based on the initial cost and 2-year HRQoL of the F group and on the reported data for joint replacement surgery, our results suggest that the cost-effectiveness of elective spine surgery for degenerative lumbar spondylolisthesis is comparable to that of joint replacement within 3 years after surgery. Posterolateral fusion (PLF) is one of the surgeries used to treat degenerative lumbar spondylolisthesis. In this study, we did not review the cost-effectiveness of PLF, because we did not perform it to treat this condition. The implant cost in PLF is generally lower than that of PLIF because it does not require interbody fusion with cages, so the cost-effectiveness of PLF could be better than that of PLIF. On the other hand, PLF is reported to be associated with a high pseudoarthrosis rate and frequent revision surgery [23]. Bydon et al. compared the cost-effectiveness of PLIF versus PLF in 137 patients with lumbar spondylolisthesis and concluded that PLIF was more cost-effective than PLF at the 3.5-year post-operation time point, because of the higher frequency of reoperation with PLF. Taken together, further study is needed to evaluate the costeffectiveness of PLF with respect to elective spine surgery for degenerative lumbar disorders [24]. 4.1. Reoperation frequencies The reoperation frequency within the three years after surgery was 12% in the D group and 7% in the F group. Five patients had recurrent spinal stenosis and received either PLIF or TLIF, one patient had both same level and adjacent level stenosis and received 2 level PLIF, and 1 patient developed post-operative hematoma and received evacuation in D group. On the other hand, 2 patients had adjacent segmental disease and one patient received TLIF and 1 patient received decompression alone. One patient had surgical site infection and received irrigation and debridement procedure in F group. Both groups had slightly better reoperation rates than previously reported for their respective procedures [3,4]. Ghogawara et al. reported a 15% frequency of reoperation within one year of D surgery for DS [10]. Blumenthal et al. reported a 37.5% reoperation frequency of D surgery for DS during a mean follow-up period of 3.6 years [12]. Deyo et al. reported a 10.6% incidence of reoperation after F for DS, and Kim et al. reported a 14.2% incidence of reoperation during a mean follow-up period of 3.5 years [11,13]. In the present study, the reoperation frequency was slightly higher in the D group (12%), resulting in an ~26% increase in total costs and a cost/QALY decrease of $728 compared to the F group. For each patient, the surgical method was selected after assessing the stability of the lumbar spine, and only patients with significant spinal instability were treated by F. Even so, the reoperation frequency was still slightly higher in the D than the F group. Significant risk factors identified for reoperation after D for DS include spinal instability, youth, being male, and preserved intervertebral disc height [5e13]. Sato et al. have previously described the incidence and independent risk factors for reoperation within five years after D or F in 163 consecutive DS patients [7], and found a cumulative reoperation rate of 10% at one year and 24% at three years after D, and 2% at one year and 8% at three years after F. Compared to our previous report, the frequency of reoperation within three years of surgery was lower for both groups in the present study, which might indicate an improvement in selecting the procedure for individual patients. Medical history can also affect the postoperative HRQoL. For instance, 9% of the D-group and 15% of the F-group patients had a history of DM; of these, one patient in each group had a surgicalsite infection requiring irrigation and debridement. Surgical-site infections are more frequent in patients with DM [25,26]. Additionally, 17% of the D-group and 15% of the F-group patients were
smokers. Several factors affect the success of spinal fusion, including age, DM, osteoporosis, and smoking [4,11,26,27], and the negative impact of smoking on bone fusion after lumbar-fusion surgery is well documented [11,27e29]. A recent study reported a clinically significant deterioration in HRQoL after elective spine surgery in patients who smoke. Thus, adequate preoperative treatment of both smoking habits and DM might reduce the risk of surgical-site infection and pseudoarthrosis thereby improving the postoperative HRQoL and the cost-utility for each method. 4.2. Superior HRQoL improvement in the F group In the present study, the three-year postoperative HRQoL was significantly better in the F than the D group, despite comparable baseline demographic data (i.e., gender distribution, mean age, smoking history, history of DM, HRQoL scores, and type of occupation). The three-year cumulative QALY was also significantly better in the F group, and the three-year ICER was comparable in the F and D groups despite the high three-year cumulative total cost in the F group. However, we cannot conclude that F is superior to D when treating DS, because of the difference of surgical indication. We chose F for only those with significant spinal instability and chose D for those without spinal instability. Several reports have demonstrated superior postoperative outcomes for F compared to D [5,10e12]. However, there is presently no consensus as to the superiority of either procedure for treating DS. In two recent RCTs comparing the effectiveness of D versus F for lumbar spinal stenosis with or without DS, both procedures significantly improved the HRQoL. However, the studies differed as to the effectiveness of the two methods. Ghogawara et al. found €rsth et al. that F improved the HRQoL slightly more than D [8], but Fo found that F did not improve the two-year or five-year clinical outcomes compared to D [9]. Both RCTs demonstrated that in most cases, stenosis surgery should be limited to D if there is no overt instability [8,9]. Surgical procedures in the present study were selected in accordance with the results of these RCTs, and improved surgical selection may have reduced the reoperations rates and improved the ICER for both methods. 4.3. Spinal implant costs in the F group Spinal-implant costs, which included the cost of sutures and bone substitute as well as spinal implants, were significantly higher in the F group. The average implant costs in the F group ($7953 ± 1564 for the initial surgery) increased the total cost in the F group by ~42% and the ICER by ~23%. Our study has some limitations. First, the study population was small and heterogeneous, which made it difficult to draw strong conclusions about the outcomes of DS surgery based on cost utility analysis results. DS patients cannot be generally categorized as to gender, age, occupation, or comorbidities, and exhibit various degrees of spinal instability [5,6]. DS causes severe disability in some patients and mild symptoms in others [5,6]. In the present study, the patients were treated by D unless there was significant instability of the spine, in which case they were treated by F. Given this selection bias, our results may not be universally representative of DS treatment. However, our experience is that neither method, D or F, can be considered universally optimal for all patients with DS. Rather, accurate selection of the appropriate surgery for each patient is key in obtaining better clinical outcomes for both methods when treating DS. Second, the 3-year post-operative follow-up term in this study was relatively short for evaluating the costeffectiveness of elective spine surgery. Previous reports describe a high revision rate for decompression and fusion surgery due to an increase in adjacent segmental disease at middle to long time
Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001
M. Yagi et al. / Journal of Orthopaedic Science xxx (2018) 1e5
periods after the operation. Therefore, the re-examination of this patient cohort at later follow-up times may provide further information about the cost-effectiveness of elective spine surgery [7]. In addition, healthcare systems vary in different countries. The national health insurance system is available in Japan, so the patient payment is consistent for high-cost treatments [17,18]. Thus, it can be assumed that there is no bias in choosing a treatment based on patient income and insurance type. However, due to the variability in healthcare systems throughout the world, caution is needed when interpretating these results for other countries. In the present study, the one-year cost/QALY exceeded the costeffective threshold in both groups. The high initial cost of orthopedic surgery highlights the importance of long follow-up periods and accurate HRQoL assessment when evaluating the cost-utility of elective spinal surgery for DS. Additionally, lower revision rates and better clinical outcomes were indispensable for improving ICERs. Thus, it is important for physicians to select the appropriate procedure for each patient and to weigh the surgical risks to avoid major complications that would require additional surgery. In this study, both methods, D and F, for treating DS were cost-effective when the technique was selected appropriately for the patient. 5. Conclusion The cost-utility of elective spine surgery for DS over a three-year postoperative period did not differ significantly between D and F. For both methods, the three-year ICER was within three times the percapita GDP for surgery. Therefore, both methods are cost-effective for the surgical treatment of DS. Further large-sample studies with long-term follow-up periods or simulation-based studies will further clarify the cost-utility of surgical treatments for DS. Conflict of interest The authors declare that they have no conflict of interest. References [1] Brauer CA, Rosen AB, Olchanski NV, Neumann PJ. Cost-utility analyses in orthopaedic surgery. J Bone Jt Surg Am. 2005 Jun;87(6):1253e9. [2] Martin CR, Gruszczynski AT, Braunsfurth HA, Fallatah SM, O'Neil J, Wai EK. The surgical management of degenerative lumbar spondylolisthesis: a systematic review. Spine (Phila Pa 1976) 2007 Jul;32(16):1791e8. [3] Ghogawala Z, Resnick DK, Glassman SD, Dziura J, Shaffrey CI, Mummaneni PV. Randomized controlled trials for degenerative lumbar spondylolisthesis: which patients benefit from lumbar fusion? J Neurosurg Spine 2017 Feb;26(2):260e6. [4] Enyo Y, Yoshimura N, Yamada H, Hashizume H, Yoshida M. Radiographic natural course of lumbar degenerative spondylolisthesis and its risk factors related to the progression and onset in a 15-year community-based cohort study: the Miyama study. J Orthop Sci 2015 Nov;20(6):978e84. [5] Pearson A, Blood E, Lurie J, Tosteson T, Abdu WA, Hillibrand A, Bridwell K, Weinstein J. Degenerative spondylolisthesis versus spinal stenosis: does a slip matter? Comparison of baseline characteristics and outcomes (SPORT). Spine 2010 Feb;35(3):298e305. [6] Weinstein JN, Tosteson TD, Lurie JD, Tosteson AN, Blood E, Hanscom B, Herkowitz H, Cammisa F, Albert T, Boden SD, Hilibrand A, Goldberg H, Berven S, An H. SPORT Investigators. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med 2008 Feb;358(8):794e810. [7] Sato S, Yagi M, Machida M, Yasuda A, Konomi T, Miyake A, Fujiyoshi K, Kaneko S, Takemitsu M, Machida M, Yato Y, Asazuma T. Revision rate and risk factors of elective spinal surgery for degenerative spondylolisthesis: minimum 5-year follow-up. Spine J 2015 Jul;15(7):1536e44.
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Please cite this article in press as: Yagi M, et al., Comparisons of direct costs, outcomes, and cost-utility of decompression surgery with fusion versus decompression alone for degenerative lumbar spondylolisthesis, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/ j.jos.2018.04.001