The Impact of Compressive and Cyclic Loading Frequency on Longitudinal Growth, Given a Constant Amplitude

Sammanfattning: Mechanical stress exerted on long bones stimulate ossification and it has been shown that the mechanical variable frequency promotes osteogenesis. This ex-vivo study aimed to investigate how compressive and cyclic loading frequency impacts longitudinal growth of long bones. Three separate experiments were performed utilizing fetal Sprague-Dawley rat bones as experimental model. In the first two trials metatarsals where used while tibias were tested in the third trial. The bones were loaded once with a material testing system, cultured in an incubator and had their length measured on several occasions throughout their growth period. Loading protocol and days of length measurement differed between the trials. The first trial failed, since all of the control bones decreased in length in relation to the day of loading, while they should at least have grown 30% on the fifth day after loading. The results obtained from the second trial indicate that the frequency 0.4 Hz has a great impact on longitudinal growth, with a length increase of 50%-60% in relation to the day of loading. A conclusion regarding the other frequencies studied could not be made due to high spread of length alteration data. The tibias from the last trial did not show any significant results. Moreover, it was concluded that compressive and cyclic loading do promote longitudinal growth, despite the great variation in length alteration for most of the bones, including the control bones. The findings of this study could serve as a foundation for a research study further investigating the relation between frequency and longitudinal growth.