The rotational molding technique was utilized in the fabrication of hollow
femur models for the expressed purpose of photostress analysis. Advances in
computer control coupled with the development of proper experimental proto
cols enabled the consistent and automated reproduction of the joint model.
Such considerations proved to be critical in overcoming the limitations of
prevailing rotational molding operations. The use of hollow rotation molded
models was advantageous as it better represented the physiologic constitut
ion of real bones, thereby, conferring a greater degree of accuracy in the
photostress experiments. The fabrication of the hollow models entailed flow
visualization studies, which assessed the variation in rotational speeds w
ith time as well as the optimum relative rotation speeds to be adopted The
preferred mode of rotational motion was also determined through a series of
simulated experiments to determine whether steady or repetitive cyclical r
otational modes were more beneficial. The fabricated hip models were loaded
and the stress profiles examined. Contour maps of the stress fringes manif
ested in the photoelastic analysis indicated several sites of stress concen
trations. These sites coincided with physiologic patterns of hip fractures,
verifying the validity of the hollow femoral models. Computer controlled r
otational molding has proven to be a feasible manufacturing process in the
development of hollow physiologically representative fern or models.