Abstract
In an attempt to work up the healing mechanism of bone fracture, an experiment was conducted on young, male Wistar strain rats, 70 to 80 gm in weight, in which the animis were allocated to 4 groups according to the procedure employed for the production of fracture of the femur and the subsequetly applied orthopedic therapeutic measures ; i.e. (1) manual subcutaneous fracture without treatment, (2) osteotomy with a chisel plus intramedullary fixation with a Kirschner wire, (3) osteotomy with an electrical bone saw without concurrent application of physiological saline plus intramedullary fixation with a Kirschner wire, and (4) the same as in (3) except for the concurrent use of physiological saline, and were then observed for the bone salt deposition status at the affected site by the use of contact-microradiography, tetracycline (Achromycin®) labelling as a tracer, 45Ca-autoradiography (strip method) and roentogenography as well as by histologic (using haematoxylin-eosin staining) and macrosccopic examination over a period from the 4 th day up to the 6 th week after the injury. The results obtained are summarized as follows:
1) In group 1, the callus formation was initially rather poor probably and partly due to the working physical factors and became adequate toward the 3 rd week with favorable calcification as evidenced by increasing deposition of TC and 45Ca. The excess callus tended then to be reduced gradually and complete bony union attained at the 6 th week.
2) The animals of Group 2 generally showed somewhat retarded callus formation in comparison with those of Group 1 initially. From toward the 3 rd week, deposition of TC and 45Ca increased, calcification of the callus became prominent, but this was somewhat slower than in Group 1. Bony union was achieved in 6 weeks.
3) In Group 3, union of the broken ends was almost completely accomplished in 6 weeks, though both callus formation and uptake of TC and 45Ca were significantly delayed initially by the action of heat generated at osteotomy.
4) In Group 4, the initial callus formation was more marked than in Group 3. At the 3 rd week ossification at the injured site was prominent with increased TC and 45Ca uptake, diminished then gradually and resulted in bony union in 6 weeks.
5) In comparison with the bone salt deposition and histological pictures in the process of fracture healing, callus formation was most favorable in Group 1, followed by Group 2, Group 4 and Group 3 in that descending order of adequacy.
6) The fact that callus formation was markedly delayed in Group 3 (without phsiological saline) stresses the necessity of cooling the bone with physiological saline at osteotomy in actual clinical cases.
7) In young rats, as compared to mature rats, the healing of the fracture generally was quicker, in parallel with which deposition of TC and 45Ca at the site of fracture was accomplished in a shorter period of time.
8) The present study corroborates that a combination of TC-labelling as a tracer, 45Ca-autoradiography and microradiography provides a useful means for a close observation of the healing process of a fracture.
