Proliferation analysis of the growth plate after diaphyseal midshaft fracture by 5'-bromo-2'-deoxy-uridine.

Both stimulative and inhibitory growth disturbances may occur after a fracture during the growth period. The exact mechanism responsible for stimulative growth disturbances in the immature skeleton is unexplained. It's possible that chondrocyte proliferation leads to overgrowth. This study investigates the effect of a fracture on the proliferation of chondrocytes at the nearby growth plate and its effect on the contra-lateral leg. Fifty-six 1-month-old Sprague-Dawley rats (weight, 100-120 g) were randomised to either an experimental or a control group. A closed mid-diaphyseal tibial fracture was produced in all animals of the experimental group using a standardised technique. On day 3, 10, 14 and 29 of the experiment, the rats were euthanised and their tibial growth plates were subjected to histological analysis. 5'-Bromo-2'-deoxy-uridine labelling was used for the quantitative analysis of chondrocyte proliferation. Safranin O staining provided the histological overview for the subsequent analysis of BrdU-labelling. Immunohistochemical analysis showed increased proliferation of chondrocytes in the growth plates of broken bones during fracture healing. This proliferation peaked on day 3 post-fracture and then reduced gradually until day 29. No increase in the rate of proliferation was observed on the contra-lateral limbs of the animals in the experimental group. Following a diaphyseal fracture of the tibia, the growth plates located next to the fracture react with increased cell proliferation. This proliferation was not observed in the contra-lateral uninjured tibia. This investigation shows that the post-traumatic length discrepancy is a local biological process at the growth plate brought about by the fracture.