24-Hour Ex Vivo Hypothermic Acellular Perfusion of Porcine Forelimb: A 7-Day Follow-up Study.

Background: One of the limiting factors for vascularized composite allograft storage is the short viable ischemic time (4 to 6 hours). Hypothermic machine perfusion enables near-physiologic 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 under hypothermic conditions for 24 hours with histidine-tryptophan-ketoglutarate ( n = 8) or preserved on ice for 4 hours (SCS; n = 8) before heterotopic replantation. Muscle injury was assessed using biochemical markers, and muscle biopsies were analyzed using the Histologic Injury Severity Score.

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 (histidine-tryptophan-ketoglutarate, n = 6; SCS, n = 6) survived for 7 days. Three days after replantation, increased creatinine kinase levels were observed in the perfusion group (33,781 versus 2163 mmol/L; P < 0.001). The mean end point Histologic Injury Severity Score 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: A total of 24 hours of hypothermic machine perfusion and 4 hours of SCS of the vascularized composite allograft demonstrated minimal degenerated muscle tissue 7 days after replantation.

Clinical Relevance Statement: This project will widely advance the field of reconstructive research and provide strong preclinical data to allow human clinical trials with great potential to change the standard of care in reconstructive transplantation.