A two-dimensional stress analysis was used to study the effects of some
of the factors leading to early fatigue failure of the femoral stem in
total hip prostheses. The results show that loss of proximal stem support
at the level of the calcar femorale will result in stem stress levels which
can lead to fatigue failure. In addition, the role of body weight and range
of cyclic stress fluctuation play an important role in fatigue life under
conditions where the stem has lost proximal support. These results indicate
that stem design could be improved by incorporating some means of ensuring
adequate support at the calcar femoralre maximum tensile stresses are found
to occur.