Cement microcracks in thin-mantle regions after in vitro fatigue loading.

An in vitro study of cemented femoral hip components was conducted to determine if microcracks in the cement mantle would preferentially form in thin-mantle regions as a result of cyclic fatigue loading via stair-climbing. Overall, there was not an increased amount of microcracks in thin-mantle (<2 mm) regions (number found/number expected = 0.59, P<.03). However, through cracks that extended between the stem to the bone were more prevalent in thin-mantle regions (number found/number expected = 2.93, P<.03). Although cracks form throughout the cement mantle and appear to grow at the same rate, thin-mantle regions are most likely to have through cracks after fatigue loading. This is consistent with results from at-autopsy studies of well-fixed femoral components and supports the general guideline that thin-mantle regions should be avoided in the cementing of the femoral stem.