dislocation(redirected from mandibular dislocation)
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dislocation,displacement of a body part, usually a bone. When a bone is dislocated, the ends of opposing bones are usually forced out of connection with one another. In the process, bruising of tissues and tearing of ligaments may occur. The condition may be congenital, but usually it is the result of injury. In some persons recurrent dislocation, usually of the jaw or of the knee, is brought on by only slight provocation. Manipulation, bandages, splints, and other appliances are used to reposition the dislocated part. Occasionally corrective surgery may be required.
displacement of the joint ends of bones, preventing them from making proper contact. Depending on the degree of displacement, dislocations can be complete (complete separation of the joint ends) or partial—subluxation (in which the joint surfaces remain in partial contact). The peripheral part of a limb (that is, the part located farther away from the trunk) is considered dislocated. For example, when the dislocation is in the knee joint, the tibia is considered dislocated; when it is in the hip joint, the femur is considered dislocated. The spine is an exception—the higher vertebra is considered dislocated.
A distinction is made between congenital and acquired dis-locations. Congenital dislocations occur as a result of mal-development of the fetus inside the uterus—underdevelopment of the joint socket and head of the femur (dysplasia). Dislocations of the hip joint are most common (two to five per 1,000 newborn); dislocation of the kneecap and knee joint are more rare. In infants, dislocation of the hip is manifested by asymmetry of the folds on the inner surface of the thighs, limited abduction of the leg, and so forth. When the infant begins to walk and later, symptoms include limping and relative shortening of one leg. In cases of bilateral dislocation, the child waddles. The symptoms of congenital dislocations of the kneecap are pain, complete immobility of the joint, inflammation of the joint, and hemarthrosis; the children walk poorly and fall frequently. Treatment of congenital dislocations of the hip—reduction and application of special splints or plaster casts—should begin as early as possible. Results are best in infants under three months old and sometimes even in children up to two years old. If the treatment shows no results in children two to four years old, surgery is indicated. Prevention includes orthopedic examination of the newborn. A child should not be tightly swaddled or, indeed, swaddled at all. The legs should not be forcibly straightened, and the child should not be made to stand up prematurely (before it stands up by itself).
Acquired dislocations are the result of injuries. They may be traumatic or caused by disease (for example, osteomyelitis and poliomyelitis), pathological or spontaneous.
In most cases traumatic dislocations are caused by indirect injury, when the place where force is applied is separated from the injured joint. (For example, a fall on the hand while the arm is outstretched may cause dislocation of the shoulder joint.) A traumatic dislocation may be caused by abrupt contraction of muscles that causes movement beyond the normal mobility of the particular joint (for example, dislocation of the lower jaw after opening the mouth too wide). Dislocations from a direct injury, such as a blow in the region of a joint, occur less frequently. Children from one to three years old may suffer from so-called dislocations from stretching, which may occur in the shoulder and elbow joints if the child’s arm is sharply jerked when he stumbles while being led by the hand. Symptoms of dislocations from stretching include severe pain in the region of the joint, deformity, and impairment or loss of movement.
The joint capsule is almost always torn in a dislocation, and the tendons, muscles, bones, blood vessels, and nerves may be injured. Such dislocations are called complicated dislocations. Dislocations may be closed—without injury to the skin over the joint—or open, when there is a wound penetrating the joint cavity. Sometimes a dislocation recurs even after slight exertion, as a result of considerable stretching of the joint capsule and ligaments or incorrect treatment. This is called a habitual dislocation, which most often affects the shoulder joint.
Pathological dislocations occur most frequently in the hip and shoulder joints as a result of destruction of the joint surfaces by a pathological process. Paralytic dislocations are found in cases of paralysis or paresis of the muscles surrounding the joint. This type of dislocation seems to arise spontaneously, without any appreciable application of external force—for example, while walking, turning in bed, and so forth.
First aid includes fixation of the injured extremity with a triangular bandage, splint, and so forth. Treatment involves reduction of the joint ends (by a physician only, in order to prevent additional traumatization of the tissues) and immobilization of the joint as soon as the diagnosis has been made; this is followed by functional therapy, including exercise and massage. Surgery is indicated for dislocations that have gone unattended for three weeks. In cases of pathological dislocations, the disease that led to the dislocation is treated. Surgery is sometimes necessary to restore functioning of the joint.
REFERENCESKhromov, B. M. Vyvikhi i perelomy, 2nd ed. Leningrad, 1960.
Volkov, M. V. Diagnostika i lechenie khronicheskogo vyvikha bedra. Moscow, 1969.
V. L. ANDRIANOV