Muscle contribution to tibial fracture strength in rats

We studied the contribution of anesthetized and dead muscle to the loading capacity of the tibia in ventral three-point cantilever bending directly by a newly developed method in rats. Ketamine anesthesia, known to give poor muscle relaxation, did not increase the loading capacity more than Hypnorm/Dormicum anesthesia and dead muscle. The ultimate bending moment increased by about 40 percent and the ultimate absorbed energy by about 85 percent when the tibia was tested in situ compared to testing in the dissected state; the tibia could withstand approximately 50 percent more deflection when loaded intact with soft tissues. No differences were observed between the tibia of anesthetized and newly-killed rats. The results indicate that the soft tissues are quantitatively important for the strength of long bones, and for the understanding and prevention of fractures.