Xenografts versus Cryopreserved Allografts for Infrainguinal Bypass Surgery: A Systematic Review and Meta-analysis

Introduction When autologous vein is not feasible for infrainguinal bypass surgery, biological alternatives are often considered due to their low susceptibility to infection. Between two commonly employed options, the cryopreserved allograft and xenograft, no comparative literature review currently exists. Methods MEDLINE, Embase and Cochrane were searched for eligible studies. Studies reporting clinical outcomes of cryopreserved allografts and/or xenografts were included. The primary outcome was primary patency at 12 months. Secondary outcomes were graft infection (<30 days and >30 days), primary assisted patency, secondary patency, limb salvage, and mortality at 12 months. Clinical outcomes were pooled for comparison using random effects models. Results Thirty-seven cohort studies met the inclusion criteria: twenty-two single-arm cryopreserved allograft studies, fourteen single-arm xenograft studies, and one comparative study. Primary patency at 12 months was comparable between cryopreserved allografts and xenografts (47.1% vs. 65.5%; p = 0.09). Early infection ( p = 0.15), late infection ( p = 0.79), secondary patency ( p = 0.19), limb salvage ( p = 0.29) and mortality ( p = 0.76) were also not statistically significant. Primary assisted patency at 12 months was significantly higher in the xenograft group (p = 0.048). Statistical heterogeneity was substantial ( I 2 > 50%) across meta-analyses, except for early graft infection ( I 2 = 0%). Conclusions Current evidence surrounding cryopreserved allografts and xenografts for infrainguinal bypass surgery suggests potentially similar outcomes. High statistical heterogeneity, heterogeneity in surgery indication and the overall very low quality of evidence limit generalizability, and should therefore not be interpreted as evidence of comparative effectiveness or superiority of either graft type. Well-designed randomized controlled trials are warranted to clarify the comparative evidence of these conduits.