Reactions of transplanted neurocentral synchondroses to different conditions of mechanical stress. A methodological study on the rat.

In order to elucidate the reactions of neurocentral synchondroses to different forces, the first cervical vertebra of 10 or 25 days old rats was transplanted into sex-matched litter mates. Some vertebrae were transplanted as a whole, in some only the ventral part with its synchondroses was transplanted and, in others the lumen was furnished with an expanding sponge or a spring. The transplantation was done subcutaneously and, in the case of the fragments, intracerebrally as well. The synchondroses of the vertebrae transplanted at 10 days did not differ very much from those of the host 5, 10 or 15 days after the operation, whereas in the vertebrae transplanted at 25 days the synchondroses underwent synostosis earlier than in situ. The synchondroses of the transplanted fragments, and especially of those placed intracerebrally, remained open longer than those in the whole vertebral transplants; the sponge and and the spring also delayed closure. In the synchondroses transplanted at 25 days there was a strong reduction in alcian blue staining, whereas in the spring loaded synchondroses the stainability persisted longer, maybe as an adaptation to the tensile force. It seems that the inherent potential of the neurocentral synchondroses to obliterate at a certain time can be altered by changing the biomechanical conditions.