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Preservation of bone graft vascularity with the University of Wisconsin cold storage solution

The preservation of the microcirculation of bone has been evaluated with use of an in vitro canine tibia perfusion model. The production of relaxing factors by the osseous vascular endothelium was used as a metabolic marker for viability. This endothelial eccrine function was preserved for 5 days (120 h) by cold storage without continuous perfusion after a washout with the University of Wisconsin (UW) solution. This synthetic perfusate was superior to Krebs Ringer solution (p < 0.05), but storage without perfusion failed to prevent a significant rise in vascular resistance. Two techniques were effective for the preservation of bone vascularity for 24 h: washout with UW solution followed by nonperfusion cold (4°C) storage, and vascular washout with mannitol solution followed by continuous hypothermic (5°C) microperfusion (0.03 ml/min) with UW solution. The most consistent, and lowest, vascular resistance was produced by the microperfusion technique. However, UW solution does not consistently prevent an increase in vascular resistance with hypothermic ischemia. This technique may prove useful for the preservation of vascularized bone grafts, but it needs to be evaluated in a transplantation model.