Application of circular statistics in the study of crack distribution around cemented femoral components

Cemented stem constructs were loaded in cyclic fatigue using stair climbing loading and the resulting fatigue damage to the cement mantle was determined in terms of angular position of crack and crack length. Techniques from circular statistics were used to determine if the distribution of micro-cracks was uniform. With a designated orientation of 0°–90°–180°–270° indicating lateral–anterior–medial–posterior anatomic directions, the overall distribution of cracks was not uniform (p<0.05) with a mean crack direction in the postero-medial (249°) quadrant of the mantle. The crack angular distribution for proximal (postero-medial; 251°) and distal (antero-medial; 112°) regions of the cement mantle was also different (p<0.025). These findings suggest that the location of cement damage depends on anatomic position and appears to correspond with the tensile stress field in the cement mantle.