24 Hours Ex-vivo Hypothermic Acellular Perfusion of Porcine Forelimb: A 7-day Follow-up Study

Background: One of the limiting factors for vascularized composite allograft (VCA) storage is the short viable ischemic time (4-6 hours). Hypothermic machine perfusion (MP) enables near-physiological preservation, avoiding the deleterious effects of hypoxia and static cooling. This study aims to compare muscle injury after 24-hour acellular perfusion with static cold storage (SCS) in a porcine limb replantation model, examining outcomes for up to 7 days after reperfusion. Methods: Sixteen procured porcine forelimbs were perfused hypothermic for 24 hours with Histidine-Tryptophan-Ketoglutarate (HTK, n=8) or preserved on ice for 4 hours (SCS, n=8) before orthotopic replantation. Muscle injury was assessed using biochemical markers and muscle biopsies were analyzed using the Histologic Injury Severity Score (HISS). Results: During preservation, limb weight decreased by 2% in the SCS group and increased by 44% in the perfusion group (p<0.001). Twelve limbs (HTK, n=6; SCS, n=6) survived for 7 days. Three days after replantation, increased creatinine kinase levels were observed in the perfusion group (33781 mmol/liter versus 2163 mmol/liter; p<0.001). Mean endpoint HISS was 3.8 (SD 0.7) in the perfusion group and 1.8 (SD 0.7) in the SCS group (p=0.008), mostly due to increased edema (p=0.004). Conclusion: 24 hours of hypothermic MP and 4 hours of SCS of VCA demonstrated both minimal degenerated muscle tissue seven days after replantation.