Injuries.—When a nail is contused or crushed, blood is extravasated beneath it, and the nail is usually shed, a new one growing in its place. A splinter driven underneath the nail causes great pain, and if organisms are carried in along with it, may give rise to infective complications. The free edge of the nail should be clipped away to allow of the removal of the foreign body and the necessary disinfection.
Trophic Changes.—The growth of the nails may be interfered with in any disturbance of the general health. In nerve lesions, such as a divided nerve-trunk, the nails are apt to suffer, becoming curved, brittle, or furrowed, or they may be shed.
Onychia is the term applied to an infection of the soft parts around the nail or of the matrix beneath it. The commonest form of onychia has already been referred to with whitlow. There is a superficial variety resulting from the extension of a purulent blister beneath the nail lifting it up from its bed, the pus being visible through the nail. The nail as well as the raised horny layer of the epidermis should be removed. A deeper and more troublesome onychia results from infection at the nail-fold; the infection spreads slowly beneath the fold until it reaches the matrix, and a drop or two of pus forms beneath the nail, usually in the region of the lunule. This affection entails a disability of the finger which may last for weeks unless it is properly treated. Treatment by hyperæmia, using a suction bell, should first be tried, and, failing improvement, the nail-fold and lunule should be frozen, and a considerable portion removed with the knife; if only a small portion of the nail is removed, the opening is blocked by granulations springing from the matrix. A new nail is formed, but it is liable to be misshapen.
Tuberculous onychia is met with in children and adolescents. It appears as a livid or red swelling at the root of the nail and spreading around its margins. The epidermis, which is thin and shiny, gives way, and the nail is usually shed.
Syphilitic affections of the nails assume various aspects. A primary chancre at the edge of the nail may be mistaken for a whitlow, especially if it is attended with much pain. Other forms of onychia occur during secondary syphilis simultaneously with the skin eruptions, and may prove obstinate and lead to shedding of the nails. They also occur in inherited syphilis. In addition to general treatment, an ointment containing 5 per cent. of oleate of mercury should be applied locally.
Ingrowing Toe-nail.—This is more accurately described as an overgrowth of the soft tissues along the edge of the nail. It is most frequently met with in the great toe in young adults with flat-foot whose feet perspire freely, who wear ill-fitting shoes, and who cut their toe-nails carelessly or tear them with their fingers. Where the soft tissues are pressed against the edge of the nail, the skin gives way and there is the formation of exuberant granulations and of discharge which is sometimes fœtid. The affection is a painful one and may unfit the patient for work. In mild cases the condition may be remedied by getting rid of contributing causes and by disinfecting the skin and nail; the nail is cut evenly, and the groove between it and the skin packed with an antiseptic dusting-powder, such as boracic acid. In more severe cases it may be necessary to remove an ellipse of tissue consisting of the edge of the nail, together with the subjacent matrix and the redundant nail-fold.
Subungual exostosis is an osteoma growing from the terminal phalanx of the great toe (Fig. 107). It raises the nail and may be accompanied by ulceration of the skin over the most prominent part of the growth. The soft parts, including the nail, should be reflected towards the dorsum in the form of a flap, the base of the exostosis divided with the chisel, and the exostosis removed.
Malignant disease in relation to the nails is rare. Squamous epithelioma and melanotic cancer are the forms met with. Treatment consists in amputating the digit concerned, and in removing the associated lymph glands.