A contusion or bruise is a laceration of the subcutaneous soft tissues, without solution of continuity of the skin. When the integument gives way at the same time, a contused-wound results. Bruising occurs when force is applied to a part by means of a blunt object, whether as a direct blow, a crush, or a grazing form of violence. If the force acts at right angles to the part, it tends to produce localised lesions which extend deeply; while, if it acts obliquely, it gives rise to lesions which are more diffuse, but comparatively superficial. It is well to remember that those who suffer from scurvy, or hæmophilia (bleeders), and fat and anæmic females, are liable to be bruised by comparatively trivial injuries.

Clinical Features.—The less severe forms of contusion are associated with ecchymosis, numerous minute and discrete punctate hæmorrhages being scattered through the superficial layers of the skin, which is slightly œdematous. The effused blood is soon reabsorbed.

The more severe forms are attended with extravasation, the extravasated blood being widely diffused through the cellular tissue of the part, especially where this is loose and lax, as in the region of the orbit, the scrotum and perineum, and on the chest wall. A blue or bluish-black discoloration occurs in patches, varying in size and depth with the degree of force which produced the injury, and in shape with the instrument employed. It is most intense in regions where the skin is naturally thin and pigmented. In parts where the extravasated blood is only separated from the oxygen of the air by a thin layer of epidermis or by a mucous membrane, it retains its bright arterial colour. These points are often well illustrated in cases of black eye, where the blood effused under the conjunctiva is bright red, while that in the eyelids is almost black. In severe contusions associated with great tension of the skin—for example, over the front of the tibia or around the ankle—blisters often form on the surface and constitute a possible avenue of infection. When deeply situated, the blood tends to spread along the lines of least resistance, partly under the influence of gravity, passing under fasciæ, between muscles, along the sheaths of vessels, or in connective-tissue spaces, so that it may only reach the surface after some time, and at a considerable distance from the seat of injury. This fact is sometimes of importance in diagnosis, as, for example, in certain fractures of the base of the skull, where discoloration appears under the conjunctiva or behind the mastoid process some days after the accident.

Blood extravasated deeply in the tissues gives rise to a firm, resistant, doughy swelling, in which there may be elicited on deep palpation a peculiar sensation, not unlike the crepitus of fracture.

It frequently happens that, from the tearing of lymph vessels, serous fluid is extravasated, and a lymphatic or serous cyst may form.

In all contusions accompanied by extravasation, there is marked swelling of the area involved, as well as pain and tenderness. The temperature may rise to 101° F., or, in the large extravasations that occur in bleeders, even higher—a form of aseptic fever. The degree of shock is variable, but sudden syncope frequently results from severe bruises of the testicle, abdomen, or head, and occasionally marked nervous depression follows these injuries.

Contusion of muscles or nerves may produce partial atrophy and paresis, as is often seen after injuries in the region of the shoulder.

In alcoholic or other debilitated patients, suppuration is liable to ensue in bruised parts, infection taking place from cocci circulating in the blood, or through the overlying skin.

Terminations of Contusions.—The usual termination is a complete return to the normal, some of the extravasated blood being organised, but most of it being reabsorbed. During the process characteristic alterations in the colour of the effused blood take place as a result of changes in the blood pigment. In from twenty-four to forty-eight hours the margins of the blue area become of a violet hue, and as time goes on the discoloured area increases in size, and becomes successively green, yellow, and lemon-coloured at its margins, the central part being the last to change. The rate at which this play of colours proceeds is so variable, and depends on so many circumstances, that no time-limits can be laid down. During the disintegration of the effused blood the adjacent lymph glands may become enlarged, and on dissection may be found to be pigmented. Sometimes the blood persists as a collection of fluid with a newly formed connective-tissue capsule, constituting a hæmatoma or blood cyst, more often met with in the scalp than in other parts.

The impairment of the blood supply of the skin may lead to the formation of blisters, or to necrosis. Death of skin is more liable to occur in bleeders, and when the slough separates the blood-clot is exposed and the reparative changes go on extremely slowly. Suppuration may occur and lead to the formation of an abscess as a result of direct infection from the skin or through the circulation.

Treatment.—If the patient is seen immediately after the accident, elevation of the part, and firm pressure applied by means of a thick pad of cotton wool and an elastic bandage, are useful in preventing effusion of blood. Ice-bags and evaporating lotions are to be used with caution, as they are liable to lower the vitality of the damaged tissues and lead to necrosis of the skin.

When extravasation has already taken place, massage is the most speedy and efficacious means of dispersing the effused blood. The part should be massaged several times a day, unless the presence of blebs or abrasions of the skin prevents this being done. When this is the case, the use of antiseptic dressings is called for to prevent infection and to promote healing, after which massage is employed.

When the tension caused by the extravasated blood threatens the vitality of the skin, incisions may be made, if asepsis can be assured. The blood from a hæmatoma may be withdrawn by an exploring needle, and the puncture sealed with collodion. Infective complications must be looked for and dealt with on general principles.