Acute Osteomyelitis, showing Purulent Foci and Accompanying Disturbance (Kocher.)
Fig. 223
Typhoid infection of bone; focus in rib. (Lexer.)
The mechanism of the infection and the lesions produced by the organism are essentially similar, and may be described together. These consist of rapid thrombosis, coagulation necrosis, and suppuration, along with the local destruction incident thereto, and with unlimited possibilities in the way of auto-intoxication from the local lesions and from the disturbance of the general economy and interference with excretion. Every severe case is accompanied by more or less of general septic intoxication, presumably from the ptomaine produced by the bacteria, while in many instances, particularly those where the bacteria at fault seem extremely virulent, the intoxication is overwhelming and the course a rapidly fatal one. Death has been known to follow within thirty-six hours after the first symptom of an acute osteomyelitis. For the average case three more or less distinct stages can usually be distinguished: first, a period of purulent infiltration, with the formation of local foci in the bone-marrow and speedy secondary involvement of the periosteum and synovial membrane; second, a period of sequestration or formation of a sequestratrum inside of an abscess cavity; third, the stage of repair.
First Stage.
—During this period there occurs violent inflammatory infiltration, localized areas becoming at first hyperemic, then infiltrated with hemorrhagic exudate, whose rapidity of production will indicate the intensity of the infection. Often at the same time are found enlargement of the spleen and hemorrhagic exudations in distant serous cavities, such as the pleura and pericardium. The locally infected areas of bone-marrow break down into collections of pus, which spread either toward the epiphyseal line or else along the Haversian canals toward the periosteum, which becomes both infiltrated and loosened. The loosening is particularly marked about the shafts rather than the joint ends, while, as a rule, that end of the bone toward which the nutrient artery is directed is the one whose epiphyses are first loosened. Nevertheless about the knee it would seem as though the lower end of the femur and upper end of the tibia are the particularly predisposed localities.
In many instances obliteration of nutrient vessels and thrombosis are early features. The area of separation of the periosteum is usually an index of the extent of deep destruction. From the periosteum the infection may extend toward the covering of the soft parts, in which case there may be a parosteal abscess, or it may perforate toward the joint cavity, leading quickly to pyarthrosis and destruction of joint structures. It would appear in children, particularly, that the epiphyseal cartilage often forms a barrier to the advancement of the lesion in the direction of the joint, and thus it happens that we have acute necrosis of the shaft of a long bone, with perforation through the periosteum at both of its ends. In adults this takes place less often, the joint ends being often primarily involved. Softening and separation of cartilages are usually secondary to the other processes. It is possible even to have the primary infection in the joint end proper, and extension therefrom to the epiphyses permitting of epiphyseal separation and extrusion of this fragment as a sequestrum. This separation occurs in many instances rapidly and before the attendant is aware of what has happened.