Influence of loading on bone growth at the growth plates in immature rat metatarsals

Abstract: Growth of different bones in children is facilitated by different mechanisms according to the anatomical site and function of the bone. Longitudinal bone formation in long and short bones occurs in the cartilaginous growth plates located at each end of the growing bone through a process known as endochondral ossification. This growth continues until a child becomes full-grown at which point the growth plate calcifies to solid bone [1]. It is still unclear how mechanical and biological factors affect bone growth. For the purpose of this study, immature rat metatarsals have been subjected to varying number of cycles (1, 5, 10 and 50 cycles) in order to better understand the effect that mechanical loading has on bone growth. This has been done using two consecutive trials. The trends in these trials were analyzed and compared. Specimens subjected to 5 cycles exhibited the most prominent effect of loading over the course of 16 days. The results of the trials reveal that immature bones are sensitive to cyclic compressive loading. The results revealed a potential threshold below which the loading resulted in an increased growth. Furthermore, simulations of longitudinal bone growth using a thermal-structural coupled analysis, with the findings from the experiment, has been performed. The model results in a stress free structure that is comparable to the growth of the experiments to a certain extent. The model also allowed incorporation of the bent growth that is observed in the experiments.