In Vivo strain measurements in rat femur
The purpose of the present study was to evaluate strain in the femora of rats during walking. Uni-directional strain gauge units were implanted. Peak strain at the anterior and medial aspects of the rat femur was compressive, while peak strain at the posterior aspect was tensile during walking. Median strain values at the anterior mid-diaphyseal aspect varied between 297x10-6 and 434x10-6. There were no statistical differences between recordings at different times after implantation as evaluated by daily measurements for one week. Neither was there any statistically significant difference in strain values between the walking speeds of 6.0, 10.2, and 14.7 m/min, or between values for right and left femur. In vitro measurements on replaced gauges corresponded within 5 per cent with results from bones where gauges had been implanted for one week. Waterproofing the strain gauge unit with a resin did not significantly affect the measurements. The method, therefore, enables studies of strain behavior of bone from small species in vivo under physiological and pathophysiological conditions.