No special type of deformity merits special attention; the condition in each case must be decided by inspection and X-ray examination.
In many of these cases, especially where the lesion affects the digits, the capability of the individual is but little impaired, whilst in other cases, where bones are absent, marked deformity and impairment of function may occur. Some of the cases, notably webbed toes, are comparatively easily corrected; other cases however, offer little chance of sufficient cosmetic or functional gain to make a surgical operation necessary or desirable.
Atrophy of Bone. Various causes may lead to atrophy of bone. The method by which atrophy is brought about is peculiar, and is due to the action of special giant cells, called osteoclasts. Wherever extensive atrophy of bone takes place, microscopic inspection shows such giant cells lying closely adjacent to the trabeculae of the bone which is being resorbed, and the trabeculae in that immediate vicinity slowly disappear under the action of these giant cells. Their action is very similar to the action of giant cells in the soft tissues about absorbable foreign bodies. This process is called lacunar resorption.
In old people the amount of absorption oftentimes is very great; the process is then termed senile atrophy. It may be marked in the skull and in the long bones, and in many cases of fracture of the neck of the femur, a moderate amount of lacunar resorption precedes the fracture which results from slight violence. In certain cases this resorptive process in old people is extreme, and leads to great fragility of the bones, with repeated fractures from slight violence, which under ordinary circumstances, would cause no injury at all.
A mere lack of use of bones may also lead to a certain amount of atrophy from lacunar resorption. This may be seen after amputations, where the stump of bone which is left from the amputation slowly undergoes lacunar resorption and sometimes a marked diminution in size. The same thing may also be seen in the bones of people who for long periods of time have been deprived of the use of their limbs, either by the application of apparatus around fractures, or by disuse for other reasons.
Lacunar resorption also occasionally follows lesions of the central nervous system, part of the atrophy being due to disuse of the limbs from the paralysis, and part of it also being dependent in some indirect way upon the nerve lesion.
Atrophy of bone also may be brought about by pressure. It is to be remembered that the bone, as a matter of fact, is not a perfectly rigid material, but that processes of new formation and resorption are constantly taking place, even under normal conditions. If, for any reason, bone is put under constant pressure, a certain amount of readjustment of the bony constituents takes place in order to adapt the bone to its altered condition. The most striking example of this sort of atrophy is perhaps the Chinese ladies’ feet, where the bones, being bent into an abnormal position, beginning early in childhood, ultimately show enormous deformity and an entire rearrangement of the trabeculae of the bone. The same thing also may be seen occasionally after pressure and deformity from contracture of muscles or from the pressure of scars. This process, which ordinarily leads to loss of function, in a certain limited number of cases aids function, for whilst certain fractures of the joints may lend to deformity of the articular facets of those joints, by absorption of certain portions and new formation in others, a readjustment of the joint surface may take place, so that a marked increase of function may occur.
A certain amount of atrophy also may be brought about by the pressure and development of tumors.
Hypertrophy of Bone. In many cases new growth of bony tissue is due to the new formation of periosteal bone, and is an expression of an attempt at repair of one or the other of the numerous destructive processes. In other cases true hypertrophy of the bone, with no connection with any reparative process, may occur.