The Impact of Small Artery Disease (SAD) and Medial Arterial Calcification (MAC) Scores on Chronic Wound and Amputation Healing: Can It Tell Us More?

Background: In 2021, Ferraresi et al. created a novel scoring system based on the impact of small artery disease (SAD) and medial arterial calcification (MAC) on wound healing. SAD and MAC scores functioned similar to Wound, Ischemia, and foot Infection (WIfI) but with minimal resource expenditure. Despite its potential, few studies have expanded on the original dataset. We aim to validate SAD's impact and MAC's impact on wound healing outcomes and determine their utility in relation to current predictive models.

Methods: Single-institution retrospective review was used to identify amputations for chronic (>1 month) podiatric wounds between 2015 and 2020. Foot X-ray (MAC) or angiography (SAD) < 6 months of index procedure was required. Primary outcomes included major amputation, wound healing, major adverse limb events, and amputation-free survival (AFS). Statistical analysis included chi-squared, 1-way analysis of variance, nonparametric correlation, Kaplan-Meier, Cox regression, and Akaike/Bayesian Inclusion Criteria model comparison.

Results: Of 136 limbs, 67 received SAD scores (0-2) and 128 received MAC scores (0-2). SAD cohorts exhibited similar comorbidity profiles with exception of coronary disease, heart failure, and chronic kidney disease. MAC cohorts were notably disparate in prevalence of multiple conditions. High mean SAD/MAC scores were seen in severe (3-vessel) below-ankle disease (P = 0.001∗ [SAD], P = 0.041∗ [MAC]). Both SAD and MAC correlated with lower mean toe pressure (P = 0.043∗ [SAD], P ≤ 0.001∗ [MAC]), while only MAC correlated with higher overall WIfI score (P = 0.029∗). No significant procedural differences were noted. However, higher readmission rates (73.9% [2] vs. 46.9% [0], P = 0.014∗) and all-cause mortality (65.2% [2] vs. 26.0% [0], P = 0.002∗) were noted with higher MAC. Survival analysis revealed higher 1-year major amputation rates (P = 0.036∗), impaired wound healing (P < 0.001∗), and lower AFS (P = 0.001∗) with increasing MAC severity. Additionally, MAC-2 patients underwent amputation at faster rates than MAC-0 patients (hazard ratio 5.25, 95% confidence interval [1.82, 9.77]) with longer times to wound healing (hazard ratio 0.21, 95% confidence interval [0.08, 0.53]). Model comparison suggested a combination of WIfI and MAC could improve accuracy of predicted time to major amputation, wound healing, and AFS.

Conclusions: MAC scoring showed significant promise both as individual predictor and adjunct to current predictive models of long-term wound healing outcomes. Routine use of MAC scoring in chronic limb-threatening ischemia evaluation, especially when noninvasive testing is unavailable, could promote timely referral for intervention and efficient resource utilization in limited-resource or critical care settings. Furthermore investigation is necessary to determine MAC's impact on revascularization and how scoring can be used to guide surgical decision-making.