Sources of Grafts.—It is convenient to differentiate between autoplastic grafts, that is those derived from the same individual; homoplastic grafts, derived from another animal of the same species; and heteroplastic grafts, derived from an animal of another species. Other conditions being equal, the prospects of success are greatest with autoplastic grafts, and these are therefore preferred whenever possible.
There are certain details making for success that merit attention: the graft must not be roughly handled or allowed to dry, or be subjected to chemical irritation; it must be brought into accurate contact with the new soil, no blood-clot intervening between the two, no movement of the one upon the other should be possible and all infection must be excluded; it will be observed that these are exactly the same conditions that permit of the primary healing of wounds, with which of course the healing of grafts is exactly comparable.
Preservation of Tissues for Grafting.—It was at one time believed that tissues might be taken from the operating theatre and kept in cold storage until they were required. It is now agreed that tissues which have been separated from the body for some time inevitably lose their vitality, become incapable of regeneration, and are therefore unsuited for grafting purposes. If it is intended to preserve a portion of tissue for future grafting, it should be embedded in the subcutaneous tissue of the abdominal wall until it is wanted; this has been carried out with portions of costal cartilage and of bone.
Individual Tissues as Grafts
The Blood lends itself in an ideal manner to transplantation, or, as it has long been called, transfusion. Being always a homoplastic transfer, the new blood is not always tolerated by the old, in which case biochemical changes occur, resulting in hæmolysis, which corresponds to the disintegration of other unsuccessful homoplastic grafts. (See article on Transfusion, Op. Surg., p. 37.)
The Skin.—The skin was the first tissue to be used for grafting purposes, and it is still employed with greater frequency than any other, as lesions causing defects of skin are extremely common and without the aid of grafts are tedious in healing.
Skin grafts may be applied to a raw surface or to one that is covered with granulations.
Skin grafting of raw surfaces is commonly indicated after operations for malignant disease in which considerable areas of skin must be sacrificed, and after accidents, such as avulsion of the scalp by machinery.
Skin grafting of granulating surfaces is chiefly employed to promote healing in the large defects of skin caused by severe burns; the grafting is carried out when the surface is covered by a uniform layer of healthy granulations and before the inevitable contraction of scar tissue makes itself manifest. Before applying the grafts it is usual to scrape away the granulations until the young fibrous tissue underneath is exposed, but, if the granulations are healthy and can be rendered aseptic, the grafts may be placed on them directly.
If it is decided to scrape away the granulations, the oozing must be arrested by pressure with a pad of gauze, a sheet of dental rubber or green protective is placed next the raw surface to prevent the gauze adhering and starting the bleeding afresh when it is removed.