Skeletal changes in the hindlimbs of bipedal rats.

Experimental bipedalism in rats has been proposed as a model for studying evolutionary and orthopedic change. This study quantified the skeletal changes which occur in the hindlimbs of these bipedal rats. Bipedalism was produced in 16 male rats by forelimb amputation during the neonatal period. The rats were sacrificed at maturity and the femurs and tibia-fibulas from randomly selected hindlimbs were weighed and measured. Out of a total of 25 parameters, only one, anteroposterior diameter of the proximal femur, was found to differ statistically between the bipedal and control groups. No changes were found in bone length, weight, or curvature. The results of other bipedal studies were reviewed, in light of these findings; and it is concluded that rats do not achieve true bipedalism, or increased hindlimb loading.