Multi-axial loading micromechanics of the cement-bone interface

There is continued interest in the maintenance and functional response of the cement-bone interface to loads that act across the interface. Recent experimental work has found that the interface is quite compliant (~10 microns/MPa) with sliding and opening occurring from shear and tensile loading conditions, respectively. In addition, this interface becomes more compliant following in vivo service (~50 microns/MPa). The question remains as to whether this micromotion is loading angle dependent. To address this question we performed multiloading angle experiments on cement-bone interface specimens. We asked three research questions: (1) does interface compliance depend on loading angle?, (2) are there appreciable coupled transverse motions?, and (3) can interface compliance be explained by contact fraction between cement and bone and source of bone (lab prepared or postmortem retrieval)?