Effects of Different Load Magnitudes on Longitudinal Growth of Immature Bones

Abstract: In vivo studies of mechanical loading on bone have suggested that load magnitude is one of the parameters that play a vital role in bone adaptation. This study examined how longitudinal growth of immature rat metatarsals is affected by different load magnitudes. The main hypotheses were that the longitudinal growth of immature bone would decrease with increased compressive load magnitude, and that the longitudinal growth would be more decelerated the higher the load mag- nitude. The three middle metatarsal bones in the back paws of 19-20 days old Sprague-Dawley rat fetuses were extracted. Metatarsal bones were loaded with 0.05 N, 0.25 N, 1.25 N and 6.25 N. Loading rate and number of cycles were constant at 0.01 mm/sec and 10 cycles respectively. Length measurements occurred every 2-3 day. Concluded from the study was that a load magni- tude of 0.05 N resulted in an increased longitudinal growth, compared to unloaded bones. For the other load magnitudes the results were insufficient and inconsistent and therefore nothing could be suggested for them. The problem remained as before and further studies are needed.