1 Introduction

Adult spinal deformity (ASD) encompasses a spectrum of malalignment disorders in skeletally mature individuals, most commonly degenerative scoliosis, kyphosis, and sagittal or coronal imbalance.^1,2 The prevalence of ASD increases sharply with age, affecting from 9 to 38 % of adults over the age of 60 and disproportionately impacting women as populations age worldwide.^1–5 Management strategies span from nonoperative modalities including physical therapy, bracing, and pain management to a variety of surgical approaches such as long-segment posterior spinal fusion.^1,2,6 These approaches are often combined with osteotomies such as pedicle subtraction or three-column osteotomies (3CO).^6–10 Lateral or transforaminal lumbar interbody fusion (LLIF, TLIF) techniques are employed to optimize alignment and fusion rates, with image-guided navigation or robotic assistance being adopted to enhance correction margins.^6–10

Despite advances in technique and perioperative care improve clinical outcomes, the economic burden of ASD care remains substantial. Direct surgical costs for ASD are driven largely by operating‐room time, spinal implants, and hospital length of stay, while indirect costs include postoperative rehabilitation, management of complications or reoperations, and lost productivity.^11–19 Single‐center and big data studies over the past five years have shown that combined anterior-posterior (AP) constructs incur 25–50 % higher index hospitalization charges than posterior-only fusions, whereas minimally invasive lateral and anterior approaches can shorten inpatient stays by 1–2 days but often carry higher implant expenses.^11,16–19 Cost‐utility analyses incorporating both direct and indirect components report that, at two years, posterior-only (PO) fusion yields a lower cost per quality‐adjusted life year (∼US $350,000) than combined AP strategies (∼US $525,000), yet methodological heterogeneity and sparse direct comparisons limit clear conclusions.^{11,16,18,20,21} Although a growing number of cost‐analysis papers have been published in the past five years, no systematic review has yet synthesized these data to guide surgeons, payers, and patients in selecting the most value-based surgical approach for ASD correction. Therefore, the purpose of this systematic review is to examine the comparative costs of various approaches and techniques utilized during complex spinal corrective surgery for ASD to inform surgical decision-making.

2 Methods

3 Results

3.1

3.1 Search results

A total of six articles were included out of 664 articles initially retrieved from the databases (Fig. 1).^{11,18,25–28} Two hundred and seventy-eight articles were excluded as duplicates followed by 345 articles being excluded by title and abstract screening. Finally, 41 articles were examined by full-text with 35 articles being excluded due to study ineligibility. No articles were found via a full reference search of the included articles or via the grey literature search. Additionally, no articles were found on the Tuft's CEA Registry.

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Fig. 1 The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) diagram.

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4 Discussion

This narrative systematic review is, to our knowledge, the first to comprehensively evaluate and compare the hospital costs and cost-utility profiles of all major surgical approaches for ASD, including LLIF, PO and combined AP fusion strategies, and various osteotomy techniques. Across the limited body of evidence, comprising one to two studies per comparison with total sample sizes ranging from fewer than 100 to several hundred patients, more complex or combined approaches consistently trended toward higher index hospitalization and two-year cumulative costs compared with TLIF or PO fusion, and osteotomies introduced an incremental cost burden in a stepwise fashion. Cost-per-QALY data were sparse and showed no clear superiority of any technique, reflecting heterogeneous methodology and underpowered study designs. While these findings underscore important economic patterns, the narrative nature and small study numbers preclude definitive conclusions and highlight the need for larger, standardized cost-effectiveness investigations in ASD surgery.

ASD procedures impose a markedly greater resource burden when compared to deformity pathologies in pediatric populations such as adolescent idiopathic scoliosis (AIS) surgery, and our cost trends mirror those overarching drivers. Meta-analyses and multicenter cohorts report that ASD cases require on average 5–8 h of OR time, which is nearly 30–60 min longer than AIS, along with a hospital stay of 6–10 days versus 4–6 days for pediatric deformity (mean difference 37.9 min, 95 % CI: −10.7 to 86.6, p = 0.127; mean length of stay (LOS) difference 0.5 days, 95 % CI: −0.2 to 1.2, p = 0.188).^29–32 In our review, LLIF incurred 29 % higher index hospitalization costs than TLIF (mean $65,937 vs. $50,945; p < 0.01) and AP fusion showed a 30–75 % cost premium over PO approaches, reflecting both extended OR utilization and more implants per case. Implant and supply expenses in ASD are driven by extensive instrumentation, osteotomies, and use of adjuncts like BMP, leading to direct hospital costs of $57,600-$116,300 at three years -- with 75.5 % in the index admission -- compared with substantially lower median AIS costs.^31,33,34 Osteotomies, often necessitated by rigid adult curves and poor bone quality, added approximately $21,000 to two-year cumulative costs versus no osteotomy (p < 0.0001), concordant with the cost escalation from complex releases and revision risk in osteoporotic spines.^5,6 Adult-specific comorbidities (e.g., coronary disease, elevated Charlson Comorbidity Index) not only prolong LOS but elevate complication rates, with perioperative complications -- particularly reoperation -- nearly doubling aggregate costs when they occur.^32,33,35 These parallels underscore that the unique anatomical and medical profile of ASD may contribute to the premium we observed for advanced fusion strategies and osteotomies, reinforcing the need for targeted cost-containment measures in this high-risk population.

Osteotomy grade, surgical approach, and exposure strategy are key procedural and system-level economic drivers in ASD surgery. Compared with grade-2 osteotomies, we observed 3COs require significantly more OR time and greater implant and supply costs, with mean initial procedure expenses of $72,240-$76,294 and cost per QALY at two years exceeding $500,000; these high-grade osteotomies also carry elevated complication risk and resource utilization.¹¹ Approach-specific differences mirror these cost escalations: LLIF averages 350 min of operative time vs, 270 min for posterior-only fusion (p < 0.01), with implant costs of $54,466 versus $41,328 (p < 0.01) and total direct hospital costs of $65,937 versus $49,849 (p < 0.01).²⁷ Combined AP fusion further prolongs surgery (548 min versus 283 min, p < 0.01), increases ICU stay and blood loss, yet may halve two-year readmission rates (9.1 % vs 38.1 %, p < 0.05).^19,36 At the system level, Medicare DRG payments do not adjust for procedural complexity, instead scaling only with length of stay ($1400–$1879 per extra five days), posterior fusion ($6588), and complications or comorbidities ($13,000).^15,34,37,38 Bundled-payment models may further contribute to the demanding economics of some practices, as cost outliers above $100,000 occur in 12–19 % of ASD cases due to fusion levels, approach, and prolonged hospitalization.^15,34,37,38 Therefore, the stratification of perioperative resources such as ambulatory clinics, imaging techniques, and perioperative staff by the complexity of each individual ASD pathology may allow patients to gain the highest level of support for their level-of care needed and minimize direct hospital related expenditures.

Although all major ASD techniques yield meaningful gains in disability and quality-of-life metrics, their two-year cost-per-QALY ratios generally exceed conventional willingness-to-pay thresholds, reflecting the substantial resource intensity of these interventions. For LLIF, the mean two-year cost-per-QALY of $463,798 accompanies a modest QALY gain of 0.18 alongside significant Oswestry Disability index (ODI) and SRS-22 improvements, yet it remains statistically indistinct from other approaches.^11,19,27 Similarly, grade-2 and 3CO demonstrate comparable QALY gains (0.13–0.15) with cost-per-QALY between $509,370 and $518,406 at two years.¹¹ PO and combined AP fusions achieve between 0.11 and 0.17 QALYs at two years for cost-per-QALY values ranging from $414,885 to $518,406, while TLIF has shown a median two-year cost-per-QALY of $45,628 with a 0.43 QALY gain at one year, though this figure derives from broader fusion literature rather than ASD-specific cohorts.^21,39 Higher expenditures do correlate with increased odds of achieving substantial clinical benefit on ODI and SRS-22 at two years (OR 2.4–3.0, p < 0.05), but the relationship is not linear; more costly procedures do not uniformly yield proportionately greater outcomes, and cost-effectiveness improves in patients with higher baseline disability and those in middle age.^12,20 Encouragingly, longer follow-up diminishes cost-per-QALY, dropping to approximately $142,058 at five years, and most patients reach acceptable cost-effectiveness when avoiding revision surgery.²¹ Taken together, these data suggest that while ASD surgery can deliver significant functional improvements, careful patient selection and strategies to minimize complications are essential to optimize the value of these high-cost interventions.

This study offers several important strengths. It is, to our knowledge, the first comprehensive, narrative systematic review to directly compare hospital costs and cost‐utility profiles across the full spectrum of surgical approaches for ASD to provide surgeons with broad insight into how procedural choice influences both short‐ and mid‐term economic outcomes. Nevertheless, several limitations warrant careful consideration. First, all included studies were retrospective observational cohorts, which introduces inherent selection bias and warrants cautious interpretation of findings. Second, the small number of studies per comparison and wide variability in sample sizes preclude formal meta‐analysis and limit this study to a narrative synthesis. Third, heterogeneity exists in cost definitions and capture windows, with some studies reporting only index hospitalization charges while others including two‐year cumulative costs or complication‐related readmissions with limited standardization of implant, supply, and indirect care expenses. Additionally, follow‐up durations varied from one to five years, limiting assessment of long‐term economic implications such as revision surgery beyond the two‐year horizon. Furthermore, the current study focused on direct hospital costs and did not incorporate societal or patient‐level factors such as return‐to‐work delays or broader healthcare expenditure which may understate the true economic burden of ASD surgery. Despite these limitations, our findings establish a foundational framework for future prospective, standardized cost‐effectiveness research in ASD.

5 Conclusion

This systematic review of cost‐utility comparisons across ASD surgical approaches observed that more complex procedures such as LLIF, combined AP fusion, and 3CO incurred greater index hospitalization and two-year cumulative costs than TLIF or posterior‐only strategies. Cost-per-QALY ratios at two years exceeded conventional willingness-to-pay thresholds for all techniques without a demonstrable superiority seen in such higher-cost approaches. Given the small number of retrospective cohorts, heterogeneity in cost definitions and capture periods, and limited utility data, these findings must be interpreted with caution. Spine surgeons should therefore weigh the increasing economic cost of advanced ASD techniques against a varying functional gain when selecting a surgical strategy. Prospective, standardized cost‐effectiveness studies with longer follow-up and uniform QALY measurement are needed to clarify the long-term value and optimize resource allocation in ASD care.

Consent statement

This study did not require patient consent or use individual patient data.

Ethical statement

This study is IRB exempt.

Author credits:

OSA, ANB, DM, KTC, GP, and JCH: drafted the work or revised it critically for important intellectual content; GT, NIC, and JV: made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data; or the creation of new software used in the work.

Funding statement

This study received no funding.