Necrosis (Gr. vkupwus, from vekpuv, to cauee to die), a term employed to denote the death or mortification of bony tissue. It bears the same relation to the bones that gangrene does to the soft parts; the part of the bone affected with necrosis becoming a foreign body, like the eschar in gangrene, which, by the efforts of nature or of art, must be removed. Necrosis is the result of inflammation of bone (ostitis), caused by injury or arrest of nutrition; it frequently follows ill-treated or badly performed amputations, and is more apt to occur in scrofulous and debilitated subjects., (See Amputation.) Inflammation of bone does not, however, always end in necrosis; for resolution may take place, or superficial suppuration. The bones of the lower extremity, particularly the femur and tibia, are those most frequently attacked, although persons engaged in making lucifer matches, or otherwise exposed to the fumes of phosphorus, often have necrosis of the jaw bones. (See Match.) Necrosis may be traumatic (from mechanical injury) or ideopathic (without immediate exciting cause); and the inflammation from which it arises may be either acute or chronic. The progress of the necrosis itself (that is, the separation of bone) is more or less slow.

The extent varies; sometimes a mere leaf of bone may perish on the external surface, a process termed exfoliation; or a large exterior section or the cancellated interior may perish. (See Bone.) The dead portion is called a sequestrum, its position depending upon whether the necrosis is external, from periostitis, or internal, from endostitis. (See Osteo-myelitis.) Necrosis usually attacks the laminated structure of the shaft rather than the cancellated or spongy portion, this being more liable to caries. (See Caries.) By avoiding the articular extremities, therefore, necrosis is not apt to be complicated with synovial inflammation, but it occasionally attacks the head of the tibia. Its progress may be divided into two stages, the inflammatory stage and the stage of separation, the latter taking place when the inflammation reaches the point of suppuration. When the necrosis is external to the shaft, the periosteum, when not destroyed, generally secretes a shell of bone outside of the dead part, and through holes in this the pus passes out.

When the inflammation is in the membrane of the canal, or endosteum, and is followed by necrosis, the sequestrum will be surrounded by a shell of the true shaft. - The symptoms of necrosis are those of inflammation of bone in general, attended by other distinguishing physical signs, such as whiteness of the exposed bone, resonance on being struck, and absence of haemorrhage if scratched. If, however, the bone retains its vitality, the color is brown, it is covered with a secretion of its own, and it bleeds when scratched. The treatment is both expectant and active. Time, pain, and much suffering may be saved by an early and free incision into the diseased part. The detachment of the sequestrum must be left entirely to nature, or assisted only by constitutional treatment, such as leeches, fomentations, and other local antiphlogistic, but often general tonic treatment, great attention being paid to supporting the strength. When the sequestrum has become wholly detached from the living bone, nature should be assisted in its removal by art. There is error in waiting too long, as the irritation of the dead part may induce too much structural change; but there is greater danger in interfering too soon, before the piece of hone becomes loose.

When a careful examination has indicated the proper time, an incision is made through the superficial soft parts; then, through the cloacae in the exterior shell of bone formed by the periosteum, the form and position of the sequestrum may be ascertained with a probe. If necessary the exterior shell must be divided by cutting pliers, and an opening sufficiently large made to admit of extraction by the forceps, which must be carefully and gently done. Amputation is sometimes required.