A Histological Study of the Fusion Process of the Human Pubic Symphysis : With Special Reference to that of the Human Mandibular Symphysis

In order to determine the fusion proceess of the pubic symphysis, a histological study was performed, using 13 fetal cases (7 males and 6 females) and 46 postnatal cases (24 males and 22 females). With the aid of the previous reports on the mandibular symphysis, it was also aimed to determine the difference between both symphysis and to characterize the fusion process of the pubic symphysis. The results were summarized as follows. 1. The symphysial area consisted of two layers : connective tissue and cartilaginous tissue layers. 2. The collagen fibers in the connective tissue layer was always slight in the amount during the fetal period, except for female cases of more than 25cm in length, showing a moderate amount of fibers. In the postnatal cases, it was only female that had a moderate amount of fibers. The connective tissue layers disappeared at the age of 2 in males and at 12 years in females. 3. The extent of the maturation of collagen fibers in the connective tissue layer was parallel to the amount of fibers in the fetal periods, followed by the constant predominance of matured fibers in the postnatal period. The array of the fibers shifted from vertical to horizontal via oblique one in the postnatal period. The first appearance of chondrocytes in the connective tissue layer was noted at the same time with the occurrence of the horizontal fibers. Subsequently, the chondrocytes increased in number with the increasing age, showing the dominant appearance at the age of 15. 4. The amount of chondrocytes in the inner part of the cartilaginous layer was always remarkable in the fetal period, followed by the reduction after birth. The chondrocytes were few after the age of 12. In the outer part of the cartilaginous layer, the first appearance of swollen chondrocytes was confirmed in the case of 21cm in length, followed by the unchanged number until 21 years after birth, when they disappeared. The first appearances of calcium deposits, columnar array of chondrocytes, provisional calcification and osteoclasts were observed in the fetal case of 31cm in length, followed by the increased degrees of appearances until birth. After birth, these findings decreased in degrees with the increasing age, showing the disappearances following the age of 19. 5. The bilateral pubic bones were connected by the chondroid tissue ; and the connection was completed at the age of 25. 6. Following the completion, the chondroid tissue underwent degeneration, necrosis and liquefaction. These degenerative changes were more dominant in females, especially in those with a history of delivery. 7. The comparison between the fusion processes of both pubic and mandibular symphysis revealed the earlier occurrence of initiation as well as completion of the latter symphysis and the later fusion of the former symphysis. Besides, the cartilaginous fusion of pubic symphysis showed the different biological significance from the mandibular symphysis, and also showed the reasonable structure for the function of the pelvis containing the pubic symphysis.