In cases of less marked bony softening, partial fractures can take place during powerful muscular contraction, as for example, in the forearm following tetanic or eclamptic convulsions.
In almost all cases in which the disease has lasted for a number of months the body length of rachitic children is less than the normal average for their age. In such cases the shortening of the bones is caused not only by the bowing but, at least in the more severe cases, by a true injury to the longitudinal growth especially in the bones of the lower extremities. In many cases there develops toward the end or after the cessation of the active stage, an almost complete absence of growth which leads to dwarfing.
An impairment, of the motor functions usually coexists with this deformity of the skeleton. Only a minority of rachitic children learn to stand or walk at a period approaching the normal; with most of them the time is postponed for months or even years. Children that are walk ing at the onset of the disease quickly lose this function. In addition to the fact that rachitic children do not learn to stand or walk at. the proper time, the majority of them use their legs very little or indeed not at all, and if one attempts to place them upon their feet their knees strike to gether. If the legs are not used at all they remain as a rule free from deformity, and in such cases the epiphyseal enlargement frequently does not occur. The upper extremities are remarkably spared in many children, but in very severe cases they too are very little used.
This disinclination to move is associated with a striking laxity of the voluntary muscles. The physiological tone is wanting in these cases, and as a result the limbs of such children can be easily placed in posi tions that are otherwise impossible except in the case of so-called "snake men" or sometimes in individuals with wide-spread atrophic paralysis. This muscular hypotonieity is greatly misinterpreted, and rachitic children are described as having an abnormal laxity of the periarticular ligaments. Hagenbach-Burkhardt refer to this abnor mal hypotonicity as a specific (rachitic) weakness of the muscles but I am far more inclined to regard it as an interception of the innervation.
In many cases the rachitic bones are distinctly sensitive to pressure, but even where this is not so, the muscular contractions can cause very severe bone pains, because at such time the tendons necessarily exert traction on the softened thickened periosteum, upon which they are inserted. It is very easy, therefore, to suppose that children learn to inhibit any nervous stimulus which might bring pain in its wake. In the later stages of the disease the deformities may mechanically render motion difficult.
Only in rare cases does faulty nutrition cause a backwardness in learning to stand or walk. Often when rachitic children do finally learn to walk they have, in severe cases after a year or so, a waddling gait and become easily tired on account of the deformity of the pelvic girdle and of the lower extremities.
Rachitis very frequently leads to the following striking clinical changes on the part of individual portions of the skeleton.
A disproportion between the face and head often exists due to the fact that the growth of the facial bones is slower than that of the bones of the skull. This dispropor tion is especially striking in the case of older individuals. In rachitis the transverse diameter of the upper jaw is decreased but is definitely increased in the sagitt al plane so that it projects forward in the mid-line like a beak. In contrast to this the under jaw is shortened in the sagit tal plane; the physiological curve in the region of the in cisor teeth is flattened, and the normal curve in the re gion of the canine teeth be comes angular. The lateral portions of the jaw converge, while its thicker lower edge turns upward and the alveo lar margin bends inward. The incisor teeth are often bent sharply inward so that when the mouth is closed there remains a space of sev veral millimetres between the lingual surface of the upper and the labial surface of the lower ones. The inner surface of the upper molars often rests against the outer surface of the lower molars. As a consequence of the lack of development of the alveolar process there not infrequently results a lack of sufficient space for the teeth.