In utero allogeneic bone transplantation in primates: roentgenographic and histological observations

Intrauterine allogeneic bone transplantation was performed on 25 monkey fetuses at 120 to 135 days of gestation. Two surgical techniques for orthotopic transplantation of the humeral midshaft were utilized: (1) A segment (5 to 7 mm) of fetal humerus was transplanted from fetus (donor) to fetus (recipient). An intramedullary pin (Kirschner orthopedic wire) was used for fixation of the severed humerus. (2) Without severing the humerus, a midshaft area (5 to 7 mm X 5 to 6 mm) was surgically ablated. A bone paste composed of crushed bone particles mixed with an agar-enriched culture medium was sculpted to fill this lesion. We used fresh frozen or fresh allograft tissue with equal success. Postsurgical observations included serial roentgenographic and histological evaluation of humeral osteogenesis, as well as postnatal assessment of limb use. The contralateral arm served as a control. Our findings indicate that the immune surveillance system of fetal monkeys may be tolerant of these bone allografts; alternatively, healing by substitution may also occur. The roentgenographic and histological results demonstrate that both of the transplantation procedures used here achieved restoration of the long bone. The use of bone paste allowed us to sculpt the allograft to the desired conformation. These results from laboratory primate models encourage continued investigation of fetal allogeneic bone transplantation, because of its ultimate potential for intrauterine repair of skeletal anomalies in man.