Exostoses

Exostoses, bony formations that have peripheral growth and rise above the surface of the bone. According to Kaufmann, exostoses should be included in the group of bone tumors-osteomas; the latter are divided into exostoses and enostoses (see Osteoma) depending on the nature of their growth. Exostoses occur as solitary and multiple forms, with the latter form, associated with impaired growth of the entire bone system, being distinguished as a separate nosological unit. Both types most often occur in long tubular bones, and their starting point is the epiphyseal cartilage line. The growth of exostoses usually ends along with the growth of the entire organism. The structure of exostoses resembles that of normal bone tissue: with spongy substance in the center (where the quantity and size of Haversian channels are quite variable), with a cortical layer on the periphery, and a thin layer of hyaline cartilage covering the surface of the exostosis, either as a continuous layer (according to Riethus) or in separate islands (according to Recklinghausen). Changes typical of various stages of enchondral bone formation are often observed in the bone tissue. In some cases, exostosis has its own bursa. The form of exostoses can be very varied: warty, on an elongated stalk-like pedicle (bone polyps, according to Tikhoi) or in the form of more massive flat bulges. Cases have been described where a spontaneous fracture of the exostosis led to the formation of a typical pseudarthrosis (Schubert, Zil'berg and others). In the etiology of solitary exostoses, some authors (Alipov, Springer, Zil'berg) attribute a certain role to trauma as a predisposing factor, especially when it affects an area close to the epiphyseal line. The clinical significance of solitary exostosis is determined by such accompanying phenomena as bone shortening, which according to Bessel-Hagen is an expression of a certain inhibitory effect of the exostosis on normal bone growth, but mainly by its relationship with adjacent tissues, with often observed phenomena from the vessels and nerves: pains, circulatory disorders due to compression, and in individual cases (Zil'berg and others) with the formation of an aneurysm of the popliteal artery or even gangrene of the limb (case of Kienbock). A rare form of solitary exostosis is the so-called exostosis bursata, in which the exostosis has its capsule, and in some cases, the formation of free bodies in its cavity was observed (cases of Braun, Kuznetsovsky - localization of exostosis in the iliac bone area, Billroth, Fehleisen - lower third of the thigh). Fischer described a case of multiple exostosis bursata. The capsule of the exostosis consists of ordinary fibrous connective tissue, looser on the inner surface, where there is formation of villous growths lined with a membrane similar to synovial. Sometimes special cartilaginous formations are observed, attached to the capsule by a thin stalk; similar formations are also encountered as free bodies. The question of the etiology and pathogenesis of exostosis bursata remains unresolved. According to Rindfleisch, exostosis bursata is formed from that part of the articular cartilage that borders the synovial membrane, and the capsule of the exostosis is therefore an eversion of the joint capsule, i.e., there is an enchondrosis. A number of authors (Bornhaupt, Neugebauer, Fischer, Recklinghausen and others) consider the capsule to be a secondary formation of the type of bursae, with Riethus making a comparison with the formation of a capsule in pseudarthrosis. Finally, Cohnheim, Ribbert, Kuznetsovsky, based on the complex relationships between the exostosis and the capsule, resembling a normal joint, as well as the analogy that exists in joint pathology (formation of cartilaginous growths and free bodies), believe that the cause of the formation of exostosis bursata lies in a detached embryonic joint rudiment, i.e., it is as if a joint teratoma. In multiple cartilaginous exostoses, so-called Cooper's exostosis cartilaginea, Virchow's ecchondrosis ossificans, Bayer's and Walter's osteodystrophia exostotica, there is a widespread lesion of the bone system with the formation of multiple exostoses, with their primary localization in the area of the epiphyseal cartilage, with impaired growth of long tubular bones and often with hereditary transmission of this condition. The onset of the condition should be attributed either to the very first years of life or to the embryonic period. According to Virchow and Cooper, exostoses develop from the displaced part of the intermediate cartilage. Bessel-Hagen sees the cause of the disease in a local violation of normal growth, however Pels-Leusden observed cases of abnormal growth in bones not affected by exostoses, which is why he believes that there are general causes affecting the violation of enchondral growth, i.e., there is a constitutional defect of the entire osteogenetic tissue as a whole. In multiple exostoses, there are always violations in body proportions, mainly of the limbs, with subsequent secondary deformation of them, shortening of fingers, asymmetrical position of the pelvis. Often there is a combination with multiple chondromas, which gave Kienbock reason to propose the name 'chondral dysplasia' for this condition. All authors pay great attention to the state of the endocrine system in exostotic disease. Rotter, and among Russian authors Ginzburg, indicate a connection of the disease with thyroid insufficiency. The hypofunction of the sex glands without impairment of their generative function may also be of importance. Thus, according to Biedl, removal of the testes leads to delayed ossification of the epiphyseal cartilage and violation of proportions between the length of the limbs and the trunk. Of the two cases described by Zakharyin, in one there was general infantilism and in the other an infantile uterus. In addition, the same author points to a constitutional factor that carriers of exostoses were the last children of multiparous mothers. In view of the fact that the pathogenesis of the disease has not yet been clarified, patients with multiple exostoses should be treated, namely surgical intervention, only in cases where due to a certain localization or sharply expressed secondary bone deformation, the statics and dynamics of the limbs are significantly impaired.