In this study, the effects of controlled tissue expansion on the survi
val of unipedicled venous flaps were investigated in rats. In three gr
oups of Lewis rats, a 3 x 6 cm unipedicled Lateral thoracic venous fla
p was studied with group 1 as control group (n = 30) without ally mani
pulation, group 2 (n = 30) where an expander was introduced under the
flap area but was not expanded and group 3 (n = 30) in which a 40 ml e
xpander was introduced under the flap area and was expanded over a per
iod of 10 days. Observations included gross and histological examinati
on, reverse microangiography, reverse flow resistance and percentage o
f survival of flaps. Group 3 (expanded) showed more angiogenesis, a be
tter delineation on microangiography, lower reverse flow resistance an
d higher survival rates as compared to group 2 (non-expanded). In the
control group the survival rate of flaps was the poorest and the flaps
showed higher rates of reverse flow resistance. Microangiography was
not successful in the control group. In a pilot project prior to this
experiment microscopic examination of the Lateral thoracic vein in 10
Lewis rats had confirmed the presence of two or three valves in this v
ein.