THE PY.EMIC AFFECTIONS OF THE BONES (OSTEOMYELITIS) Etiology and Pathologic Anatomy.—The bones arc infected either from an infection in the neighboring tissues or, far more frequently, through the blood current (htematogenous infection), osteomyelitis after croupous pneumonia (Peer, vol. iii).
The inflammation usually begins in the bone-marrow, where the germs circulating in the blood are deposited and destroyed by the bactericidal substances in the leucocytes (Wassermann).
Should the power of resistance of the bone-marrow be lessened (trauma) or the germs be highly virulent, then the bacteria will be vic torious, producing purulent inflammation and at the same time poison ing and killing the marrow cells. In some rare cases this inflammation may be caused by bacterial thrombi which are caught in the fine terminal arteries of the bone near the epiphyses (Fig. 110. Plate 10). Only very rarely does the infection enter from without through the periosteum.
The suppuration always proceeds through the Baversian canals and reaching the periostetun causes a periostitis which raises it from the bone (Fig. 111, Plate 10). The bone being bathed in pus on all sides succumbs to necrosis, and the size of the necrotic piece varies according to the extent with which nutrition is interfered with and may at times the whole of the diaphysis. A layer of granulations forms at the border between the healthy awl the diseased bone which gradually separates them, and which attempts to dissolve this "sequestrum," eroding it on all sides (Fig. 1101,, Plate 10).
At the same time reparative processes will take place as in all inflam mations; the periosteum forms new bone in excess which surrounds the sequestrum as an "involuerum," it is perforated by many eloaex for the discharge of the pus, and it slowly solidifies from a pasty to a solid and firm plate.
The pus burrows through the soft parts to the surface, causing mul tiple fistula.. Even large sequestra may be removed in the course of some years through the dissolving action of the granulation fissile and the process may heal spontaneously, provided, however, that the patient does not die in the meantime from the severity of the disease or from the long-continued suppuration (atnyloid disease).
The disease is most frequent in the second stage of childhood, and it is observed oftener in boys than in girls, a fact which may depend upon the chances of injury; it is, however, by no means rare in infancy (Mohr, Broca).
The reason why the youthful bone is oftener affected may be found in its vascularity and in the abundance of cells of the bone-marrow in comparison to the fatty marrow of the adult (Lexer).
The long bones are the favorite sites of the disease; first in order is the lower tnetaphysis of the femur, then the upper end of the tibia, more rarely the humerus, the lower ends of the bones of the arm and leg, and the ribs. The short small hones, which are more subject to tuberculosis (vertebrae, sacrum, phalanges), are only exceptionally affected.
The symptoms and course are characteristic. A healthy child is taken ill suddenly with high fever and pain in the affected hone; in some cases a pneumonia or pleurisy may have preceded. Through the swollen soft parts we can palpate distinctly the thickened bone, the superficial veins appear dilated, the skin feels hot, the regional lymph-nodes are enlarged and painful.
The X-ray photograph will show a peculiar double contour around the affected bone after a very few days, due to the raised-off periosteum and the newly-formed bone arising from this (Fig. 111 and Fig. 112b, Plate 10). When we cut down upon the summit of the swelling and work through the soft parts, which are infiltrated with serum down to the bone, we find pus either under or above the periosteum and under this the white necrotic bone.
In the bone-marrow itself we find larger foci (marrow-phlegmon) and small disseminated foci near the epiphyseal line. These latter may either break through the epiphysis or may cause separation of the epiphysis, or they may finally destroy the epiphysis and invade and infect the joint. The infectious material may likewise be carried through the blood into the other bones (multiple purulent osteomyelitis).