Effect of fracture on longitudinal bone growth in rats.

The growth rate in proximal tibia and distal radius in rats was investigated by the tetracycline method after femoral fracture, tibiofibular fracture, and metatarsal fracture. Up to 1 to 2 weeks after the fracture, a higher growth rate was recorded on the fractured side than on the unfractured side. This effect occurred later after tibiofibular fracture than after femoral and metatarsal fracture, but was almost of the same size and about 8 per cent of the normal growth rate. This difference in growth rate was caused partly by a general group retardation compared with the normal growth rate, and partly by a local growth stimulation in the fractured extremity. The growth retardation was pronounced after tibiofibular fracture, but was insignificant after femoral and metatarsal fracture. The growth rate on the fractured side after the latter two types of fractures was higher than under normal conditions. Thirty days after all types of fractures, the growth rate was normal, both in fractured extremity and in other growth regions.