Manual of Surgery, Alexis Thomson [new books to read txt] 📗

of the brain or spinal cord in man ever takes place. Any loss of substance is replaced by cicatricial tissue.

The repair of Bone, Blood Vessels, and Peripheral Nerves is more conveniently considered in the chapters dealing with these structures.

Rate of Healing.—While the rate at which wounds heal is remarkably constant there are certain factors that influence it in one direction or the other. Healing is more rapid when the edges are in contact, when there is a minimum amount of blood-clot between them, when the patient is in normal health and the vitality of the tissues has not been impaired. Wounds heal slightly more quickly in the young than in the old, although the difference is so small that it can only be demonstrated by the most careful observations.

Certain tissues take longer to heal than others: for example, a fracture of one of the larger long bones takes about six weeks to unite, and divided nerve trunks take much longer—about a year.

Wounds of certain parts of the body heal more quickly than others: those of the scalp, face, and neck, for example, heal more quickly than those over the buttock or sacrum, probably because of their greater vascularity.

The extent of the wound influences the rate of healing; it is only natural that a long and deep wound should take longer to heal than a short and superficial one, because there is so much more work to be done in the conversion of blood-clot into granulation tissue, and this again into scar tissue that will be strong enough to stand the strain on the edges of the wound.

The Transplantation or Grafting of Tissues

Conditions are not infrequently met with in which healing is promoted and restoration of function made possible by the transference of a portion of tissue from one part of the body to another; the tissue transferred is known as the graft or the transplant. The simplest example of grafting is the transplantation of skin.

In order that the graft may survive and have a favourable chance of “taking,” as it is called, the transplanted tissue must retain its vitality until it has formed an organic connection with the tissue in which it is placed, so that it may derive the necessary nourishment from its new bed. When these conditions are fulfilled the tissues of the graft continue to proliferate, producing new tissue elements to replace those that are lost and making it possible for the graft to become incorporated with the tissue with which it is in contact.

Dead tissue, on the other hand, can do neither of these things; it is only capable of acting as a model, or, at the most, as a scaffolding for such mobile tissue elements as may be derived from, the parent tissue with which the graft is in contact: a portion of sterilised marine sponge, for example, may be observed to become permeated with granulation tissue when it is embedded in the tissues.

A successful graft of living tissue is not only capable of regeneration, but it acquires a system of lymph and blood vessels, so that in time it bleeds when cut into, and is permeated by new nerve fibres spreading in from the periphery towards the centre.

It is instructive to associate the period of survival of the different tissues of the body after death, with their capacity of being used for grafting purposes; the higher tissues such as those of the central nervous system and highly specialised glandular tissues like those of the kidney lose their vitality quickly after death and are therefore useless for grafting; connective tissues, on the other hand, such as fat, cartilage, and bone retain their vitality for several hours after death, so that when they are transplanted, they readily “take” and do all that is required of them: the same is true of the skin and its appendages.

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.

Methods of Skin-Grafting.—Two methods are employed: one in which the epidermis is mainly or exclusively employed—epidermis or epithelial grafting; the other, in which the graft consists of the whole thickness of the true skin—cutis-grafting.

Epidermis or Epithelial Grafting.—The method introduced by the late Professor Thiersch of Leipsic is that almost universally practised. It consists in transplanting strips of epidermis shaved from the surface of the skin, the razor passing through the tips of the papillæ, which appear as tiny red points yielding a moderate ooze of blood.

The strips are obtained from the front and lateral aspects of the thigh or upper arm, the skin in those regions being pliable and comparatively free from hairs.

They are cut with a sharp hollow-ground razor or with Thiersch's grafting knife, the blade of which is rinsed in alcohol and kept moistened with warm saline solution. The cutting is made easier if the skin is well stretched and kept flat and perfectly steady, the operator's left hand exerting traction on the skin behind, the hands of the assistant on the skin in front, one above and the other below the seat of operation. To ensure uniform strips being cut, the razor is kept parallel with the surface and used with a short, rapid, sawing movement, so that, with a little practice, grafts six or eight inches long by one or two inches broad can readily be cut. The patient is given a general anæsthetic, or regional anæsthesia is obtained by injections of a solution of one per cent. novocain into the line of the lateral and middle cutaneous nerves; the disinfection of the skin is carried out on the usual lines, any chemical agent being finally got rid of, however, by means of alcohol followed by saline solution.

The strips of epidermis wrinkle up on the knife and are directly transferred to the surface, for which they should be made to form a complete carpet, slightly overlapping the edges of the area and of one another; some blunt instrument is used to straighten out the strips, which are then subjected to firm pressure with a pad of gauze to express blood and air-bells and to ensure accurate contact, for this must be as close as that between a postage stamp and the paper to which it is affixed.

As a dressing for the grafted area and of that also from which the grafts have been taken, gauze soaked in liquid paraffin—the patent variety known as ambrine is excellent—appears to be the best; the gauze should be moistened every other day or so with fresh paraffin, so that, at the end of a week, when the grafts should have united, the gauze can be removed without risk of detaching them. Dental wax is another useful type of dressing; as is also picric acid solution. Over the gauze, there is applied a thick layer of cotton wool, and the whole dressing is kept in place by a firmly applied bandage, and in the case of the limbs some form of splint should be added to prevent movement.

A dressing may be dispensed with altogether, the grafts being protected by a wire cage such as is used after vaccination, but they tend to dry up and come to resemble a scab.

When the grafts have healed, it is well to protect them from injury and to prevent them drying up and cracking by the liberal application of lanoline or vaseline.

The new skin is at first insensitive and is fixed to the underlying connective tissue or bone, but in course of time (from six weeks onwards) sensation returns and the formation of elastic tissue beneath renders the skin pliant and movable so that it can be pinched up between the finger and thumb.

Reverdin's method consists in planting out pieces of skin not bigger than a pin-head over a granulating surface. It is seldom employed.

Grafts of the Cutis Vera.—Grafts consisting of the entire thickness of the true skin were specially advocated by Wolff and are often associated with his name. They should be cut oval or spindle-shaped, to facilitate the approximation of the edges of the resulting wound. The graft should be cut to the exact size of the surface it is to cover; Gillies believes that tension of the graft favours its taking. These grafts may be placed either on a fresh raw surface or on healthy granulations. It is sometimes an advantage to stitch them in position, especially on the face. The dressing and the after-treatment are the same as in epidermis grafting.

There is a degree of uncertainty about the graft retaining its vitality long enough to permit of its deriving the necessary nourishment from its new surroundings; in a certain number of cases the flap dies and is thrown off as a slough—moist or dry according to the presence or absence of septic infection.

The technique for cutis-grafting must be without a flaw, and