—To the portion of bone which dies is given the name sequestrum, while multiple sequestra are by no means uncommon. The sequestrum is white and ivory-like in hardness when it consists of original compact structure. It is rare to find a distinct sequestrum of spongy tissue, as this yields so readily to the presence of granulation tissue and of pyogenic infection. A sequestrum may include an entire bone shaft, or epiphysis, or only a small fragment. A portion of the bone having lost its vitality becomes a foreign body which the surrounding tissues endeavor to extrude or to wall off and surround. The extrusive effort is the one which is usually seen. This is done by the continued presence of granulation tissue, which gradually perforates the surrounding bone at places of least resistance, the result being the slow formation of a sinus or several sinuses, ultimately connecting with the surface, and in which in neglected cases the dead fragment of bone can be seen or felt, or from which it can be withdrawn almost without operation. While this weakening of bone is going on in certain portions a corresponding strengthening process is also being put into effect; and the result is a quantity of new bone, which is often wrapped around the sequestrum and is simply the effort to atone for its pathological weakness and to strengthen it. This new osseous tissue which so often surrounds the sequestrum is called the involucrum, and in many instances it is necessary to remove more or less of the involucrum before the sequestrum can be lifted out of its bed or removed. (See [Plate XXXVII].)
The whole necrotic process is intelligible if read aright as an endeavor on the part of Nature to get rid of dead and irritating material. When this effort is properly interpreted the natural efforts can be seconded by the interference of the surgeon at a time when disturbance is limited to the minimum and before external sinuses have had opportunity to form. On the other hand, ignorance and neglect may lead to the extreme condition, and most fantastic arrangements of sequestra and involucra are seen in all pathological museums, some of which seem to partake almost of the perplexities of Chinese puzzles. The explanation, however, is always as above afforded. (See [Figs. 233], [234] and [235].)
Treatment.
—The treatment should be surgical, and consist in removal of the dead portions and restoration of the parts to a condition favoring rapid regeneration. It should always be radical, but is sometimes made difficult by the inaccessibility of the fragment or by the density of the involucrum and the necessity for large external openings in order to remove the sequestrum.
Large and powerful forceps and strong and well-tempered bone chisels are usually necessary, while, after making the necessary opening for removal of the sequestrum, the sharp spoon should be used thoroughly to scrape away all the lining material of cavities in which fragments have been lying or all fungous tissue which may fill sinus tracks. It will be well after this to thoroughly cauterize the wall of the cavity, after which it is to be packed.
Fig. 233
Fig. 234
Fig. 235