Contracted scars frequently cause deformity either by displacing parts, such as the eyelid or lip, or by fixing parts and preventing the normal movements—­for example, a scar on the flexor aspect of a joint may prevent extension of the forearm (Fig. 63).  These are treated by dividing the scar, correcting the deformity, and filling up the gap with epithelial grafts, or with a flap of the whole thickness of the skin.  When deformity results from depression of a scar, as is not uncommon after the healing of a sinus, the treatment is to excise the scar.  Depressed scars may be raised by the injection of paraffin into the subcutaneous tissue.

Painful Scars.—­Pain in relation to a scar is usually due to nerve fibres being compressed or stretched in the cicatricial tissue; and in some cases to ascending neuritis.  The treatment consists in excising the scar or in stretching or excising a portion of the nerve affected.

Pigmented or Discoloured Scars.—­The best-known examples are the blue coloration which results from coal-dust or gunpowder, the brown scars resulting from chronic ulcer with venous congestion of the leg, and the variously coloured scars caused by tattooing.  The only satisfactory method of getting rid of the coloration is to excise the scar; the edges are brought together by sutures, or the raw surface is covered with skin-grafts according to the size of the gap.

Hypertrophied Scars.—­Scars occasionally broaden out and become prominent, and on exposed parts this may prove a source of disappointment after operations such as those for goitre or tuberculous glands in the neck.  There is sometimes considerable improvement from exposure to the X-rays.

Keloid.—­This term is applied to an overgrowth of scar tissue which extends beyond the area of the original wound, and the name is derived from the fact that this extension occurs in the form of radiating processes, suggesting the claws of a crab.  It is essentially a fibroma or new growth of fibrous tissue, which commences in relation to the walls of the smaller blood vessels; the bundles of fibrous tissue are for the most part parallel with the surface, and the epidermis is tightly stretched over them.  It is more frequent in the negro and in those who are, or have been, the subjects of tuberculous disease.

[Illustration:  FIG. 106.—­Recurrent Keloid in scar left by operation for tuberculous glands in a girl aet. 7.]

Keloid may attack scars of any kind, such as those resulting from leech-bites, acne pustules, boils or blisters; those resulting from operation or accidental wounds; and the scars resulting from burns, especially when situated over the sternum, appear to be specially liable.  The scar becomes more and more conspicuous, is elevated above the surface, of a pinkish or brownish-pink pink colour, and sends out irregular prolongations around its margins.  The patient may complain of itching and burning, and of great sensitiveness of the scar, even to contact with the clothing.