Defining a Surgical Invasiveness Threshold for Increased Risk of a Major Complication Following Adult Spinal Deformity Surgery

Brian J. Neuman, MD; Andrew B. Harris, BS; Eric O. Klineberg, MD; Richard A. Hostin, MD; Themistocles S. Protopsaltis, MD; Peter G. Passias, MD; Jeffrey L. Gum, MD; Robert A. Hart, MD; Michael P. Kelly, MD; Alan H. Daniels, MD; Christopher P. Ames, MD; Christopher I. Shaffrey, MD; Khaled M. Kebaish, MD


Spine. 2021;46(14):931-938. 

In This Article

Abstract and Introduction


Study Design: Retrospective review.

Objectives: The aim of this study was to define a surgical invasiveness threshold that predicts major complications after adult spinal deformity (ASD) surgery; use this threshold to categorize patients into quartiles by invasiveness; and determine the odds of major complications by quartile.

Summary of Background Data: Understanding the relationship between surgical invasiveness and major complications is important for estimating the likelihood of major complications after ASD surgery.

Methods: Using a multicenter database, we identified 574 ASD patients (more than 5 levels fused; mean age, 60 ± 15 years) with minimum 2-year follow-up. Invasiveness was calculated as the ASD Surgical and Radiographic (ASD-SR) score. Youden index was used to identify the invasiveness score cut-off associated with optimal sensitivity and specificity for predicting major complications. Resulting high- and low-invasiveness groups were divided in half to create quartiles. Odds of developing a major complication were analyzed for each quartile using logistic regression (alpha = 0.05).

Results: The ASD-SR cutoff score that maximally predicted major complications was 90 points. ASD-SR quartiles were 0 to 65 (Q1), 66 to 89 (Q2), 90 to 119 (Q3), and ≥120 (Q4). Risk of a major complication was 17% in Q1, 21% in Q2, 35% in Q3, and 33% in Q4 (P < 0.001). Comparisons of adjacent quartiles showed an increase in the odds of a major complication from Q2 to Q3 (odds ratio [OR] 1.8; 95% confidence interval [CI]: 1.0–3.0), but not from Q1 to Q2 or from Q3 to Q4. Patients with ASD-SR scores ≥90 were 1.9 times as likely to have a major complication than patients with scores <90 (OR 1.9, 95% CI 1.3–2.9). Mean ASD-SR scores above and below 90 points were 121 ± 25 and 63 ± 17, respectively.

Conclusion: The odds of major complications after ASD surgery are significantly greater when the procedure has an ASD-SR score ≥90. ASD-SR score can be used to counsel patients regarding these increased odds.

Level of Evidence: 3


Surgical correction of adult spinal deformity (ASD) can greatly improve a patient's quality of life.[1–5] Although major advances have been made recently in surgical techniques for ASD surgery, complications remain a concern. Methods of classifying postoperative complications in ASD patients vary among studies, resulting in reported rates of major complications ranging from 11% to 51%.[6–10] Studies have described risk factors for complications after ASD surgery, including major blood loss, neurological complications,[11] junctional kyphosis,[12–14] and the need for revision surgery.[15,16]

Although it is important to understand how certain factors may modify a patient's risk of complications, ASD is a heterogeneous condition with similarly heterogeneous options for surgical treatment. Thus, many surgical and radiographic factors vary among patients. Some patients may require short thoracolumbar fusions for correction of mild deformity, whereas others may need arthrodesis of many vertebrae and a three-column osteotomy to achieve adequate deformity correction. The ASD Surgical and Radiographic (ASD-SR) score was developed and validated to quantify the degree of invasiveness of ASD surgical procedures, allowing better prediction of estimated blood loss and operative time.[11] Certain variables used to calculate the ASD-SR score, such as three-column osteotomy and the number of levels fused, are associated with increased risk of complications,[17] but the ASD-SR score has not been used to assess overall risk of major complications.

The objectives of this study were to define a surgical invasiveness threshold that predicts increased odds of major complications after surgical treatment of ASD; use this threshold to categorize patients into quartiles defined by invasiveness cutoff score; and determine the odds of major complications in each invasiveness quartile. Secondarily, we sought to identify the association between this invasiveness threshold and the odds of minor complications. The ASD-SR score can be calculated easily by surgeons and accounts for many of the surgical and radiographic risk factors known to modulate complication risk in ASD patients. Thus, defining a surgical invasiveness threshold for major complications will allow for more personalized patient counseling during the perioperative period and will elucidate the ability of the ASD-SR score to accurately predict the risks associated with ASD procedures according to their invasiveness.