A systematic review of the associations between aortic curvilinearity and preoperative abdominal aortic aneurysm outcomes

Objective: Traditional assessment of abdominal aortic aneurysm (AAA) progression has focused primarily on maximum transverse diameter. Emerging evidence, however, suggests that the metrics of other AAA geometric characteristics may enhance predictions of aneurysm growth and rupture risk. This systematic review aims to evaluate associations between curvilinearity metrics and AAA outcomes, while examining methodological variability within the literature. Methods: A systematic review was conducted in accordance with PRISMA guidelines. PubMed, Scopus, and Web of Science databases were searched from inception through December 2024 for human studies investigating the relationships between aortic curvilinearity metrics (tortuosity, curvature, and angulation) and AAA outcomes (growth or rupture). We included only studies in which these metrics represented primary variables; exclusions included non-AAA studies, patients with previous aortic interventions, and nonoriginal research. A total of 24 studies met the inclusion criteria. Quality was assessed using the Risk of Bias in Nonrandomized Studies of Interventions tool. Results: The 24 studies identified used three primary curvilinearity approaches: (1) tortuosity indices calculated from centerline length ratios, (2) angulation measurements quantifying vessel orientation changes, and (3) continuous curvature-based metrics assessing local bending. Among the four studies addressing AAA growth, three reported a significant positive association between increased curvilinearity and accelerated aneurysm expansion. Of the 20 studies evaluating AAA rupture risk, 17 demonstrated a significant positive association with greater curvilinearity. Considerable heterogeneity in centerline definitions, measurement end points, and computational algorithms limited direct comparisons across studies. Conclusions: Our review indicates that increased aortic curvilinearity is associated with accelerated AAA growth and a higher rupture risk. Incorporating curvilinearity metrics into AAA risk models may support a more individualized and refined clinical management. However, methodological inconsistencies, particularly regarding centerline definitions and control for confounding variables, need to be addressed. Future prospective studies employing standardized measurement protocols are necessary to validate the predictive utility of curvilinearity and promote its adoption in clinical practice.