Although free tissue transfer success has been greatly improved by dev
elopments in operating microscopes, microsutures, microinstruments, an
d technique, free flap and replant failure remain a significant proble
m under certain adverse circumstances. The nature of these failures is
often multifactorial and remains poorly understood. A greater underst
anding of the processes involved would provide the potential for great
er pharmacological control of any adverse conditions prevailing and wo
uld thus offer the prospect of more effective adjunctive therapy in th
e presence of such adverse conditions. Research endeavors in this area
have been hindered by the absence of good research models. The isolat
ed rat cremaster muscle model is a recently developed model that simul
ates the conditions of free tissue transfer. Using this model, both th
rombus formation and numerous microcirculatory parameters can be measu
red. The microcirculatory parameters studied to date include the forma
tion of thromboembolism, capillary perfusion, vessel diameters, red bl
ood cell velocity, leukocyte-endothelium interaction, and microvascula
r leakage. The isolated rat cremaster muscle model addresses many of t
he shortcomings of earlier research models and offers the promise of a
nswering at least some of the many unanswered questions relating to fr
ee flap and replant failure.