Predictive Ability of the Pedal Medial Arterial Calcification Score for Major Adverse Limb Events Among Patients with Chronic Limb-Threatening Ischemia

Background: Pedal medial arterial calcification (pMAC) is a potential predictor of major adverse limb events (MALEs) among patients with critical limb-threatening ischemia (CLTI). This study aims to validate the prognostic value of the pMAC score in predicting major lowerlimb amputation (MLLA) and need for redo revascularisation. Methods: A single-center study involving 196 patients diagnosed with CLTI, reviewed between 2012 and 2022. Patients' pMAC scores were obtained through X-ray assessments. Correlations between pMAC scores and the incidence of MALE and redo revascularization, were analyzed. A power analysis using G* Power 3 software determined a needed sample size of 157 participants. Whitney, Kaplan-Meier with log-rank test, and Cox regression for predictor identification. Results: The cohort was predominantly male (79.1%) and diabetic (59.2%). Redo revascularization need was 15.3%, increasing with pMAC scores: 3.3% (low), 24.5% (medium), and 50% (high) (P < 0.001). MLLA frequency also rose with pMAC scores: 6.7%, 27.5%, and 50% respectively (P < 0.001). Higher pMAC scores correlated with a higher incidence of MALE (P = 0.029). Multivariate analysis showed medium pMAC (hazard ratio (HR) 4.159, P = 0.002), high pMAC (HR 7.366, P = 0.015), and Global Limb Anatomic Staging System (GLASS) stage 3 (HR 3.529, P = 0.011) as independent MLLA predictors. Redo revascularization predictors included female sex (HR 2.106, P = 0.063), Black race (HR 64.498, P = 0.001), medium pMAC (HR 6.812, P = 0.002), high pMAC (HR 11.455, P = 0.008), and GLASS stage 3 (HR 2.899, P = 0.037). Conclusions: The pMAC score effectively predicts MALE in CLTI patients and enhances risk stratification. Using both, pMAC scores and GLASS stages enhances predictive accuracy, identifying patients at higher risk for MLLA, informing clinical decision-making and therapeutic strategies.