allow any inflammation and spasm of vessel walls, induced by the procedure, to subside prior to the operation.
It is preferable to connect the vessels of the free flap to the regional vessels using end-to-side anastomosis.23 This has the advantage of preserving distal blood supply and avoids problems associated with anastomosing vessels of different diameter. Simple linear slit arteriotomy is usually used, although excision of an elliptical portion of the vessel wall may make anastomosis easier in large thick walled vessels or in those with calcified or atherosclerotic walls. Excision of vein wall is almost never indicated (Fig. 7.5). End-to-end anastomosis is occasionally useful, particularly for damaged vessels with no distal run off. No difference has been noted between any of these different techniques nor is there any experimental evidence that there is any advantage of one over the other.
There is often-unjustified-concern about the "single vessel leg". An end-to-side anastomosis can always be done safely in these legs, but it should not be done within the zone of injury because dissection is difficult, the vessels are friable and throm-bosed veins are commonly encountered.
In extremities where a bypass vein graft has been used to restore circulation it is sometimes possible to use the bypass graft immediately, before scarring develops, for free flap circulatory attachment.
The choice of which vein to use for free flap drainage may be a difficult one. The deep companion veins are often thrombosed in severely traumatized extremities. It is then best to use a superficial vein for free flap venous drainage. For this reason when large superficial veins are encountered during the initial incision they should be preserved. In the lower extremity it is also sometimes possible to mobilize either the long or the short saphenous vein leaving the upper end in situ. The thick-walled
Fig. 7.4. F) Bone scan demonstrating viability of the transferred osseous flap.
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