2. Non-carious, congenital, and acquired deformities.
Tuberculous lesions do not differ in pathology or other respects from the tuberculous diseases of bones and joints described in earlier chapters of this work. Inasmuch, however, as some of them form distinct and clinical types of deformity they assume an importance which justifies reasonable consideration by themselves. Of these we shall consider spinal caries, sacro-iliac disease, hip disease, and tumor albus.
SPINAL CARIES, SPONDYLITIS, KYPHOSIS, POTT’S DISEASE.
These various terms have reference to deformities of the spine of similar type, but with considerable variations, produced by caries (tuberculosis) of the vertebral column. Where osseous structures are separated by cartilaginous or more or less complete joint cavities the primary focus may form within the spongy structures of the vertebral bodies or in the softer tissues of the intervertebral joints. In other words, it is caries of the ordinary type which assumes special significance only because of the accident of its location. The entire vertebral column should be regarded as the main support of the body, while to it is due the maintenance of the erect position which raises man above the animal. When diseased and softened it yields to pressure, the result being exaggeration or distortion of its natural curves. As the instinctive tendency of the human being is to maintain the head in the line of the centre of gravity above the pelvis, any marked degree of curvature in one direction brings about, by natural causes, a compensatory curve in its opposite direction. A well-marked case of kyphosis, then, is characterized by more than one exaggerated curvature or protuberance, one being due to disease, the other to compensation.
While there may be several foci of active tuberculous disease, even in one vertebra, there may be found pronounced forms of angular curvature as the result of destruction occurring in but one or two of them. The carious process once begun may be checked at any point in its course, or it may proceed to complete softening and destruction, with formation of cold abscess. The tuberculous process once begun spares no tissue, and thus bone and intervertebral cartilage melt and disappear in the same manner. There may be a possible danger from spreading of tuberculous disease to the spinal meninges or to the cord, or of its being generalized. In the former case there is pachymeningitis and myelitis with paralysis; in the latter case it causes more or less rapid, acute general tuberculosis. Paralysis is more often induced, however, by actual compression than by mere tuberculous involvement, although the disease products which cause this pressure are likely to come from a caseous pachymeningitis.
The disease is most common in childhood, about 80 per cent. of cases occurring before puberty. Of the three regions of the spine the thoracic is the one most often involved, next the lumbar, and lastly the cervical. The most common site of all is in the lower dorsal region. Deformity once established as the result of this disease cannot be expected to spontaneously disappear.
Causes.
—Slight injuries occurring in those of tuberculous diathesis, by which there is produced a focus of least resistance, or secondary infections following upon such conditions as scarlatina and typhoid, constitute the most frequent recognizable causes. There can usually be obtained a history of some injury in about half of the cases. The disease once established may assume either an acute or chronic type.
Symptoms.
—As indicated when discussing caries in joints the principal signs and symptoms are pain, muscle spasm, muscle atrophy, tenderness, deformity, and impairment of function. These are all present in Pott’s disease, to which they give that distinct clinical picture which Pott so graphically described about a century ago.