Acetabular shell deformation as a function of shell stiffness and bone strength

This study aimed to model shell deformation as a process of shell stiffness and bone strength. A cohort of 32 shells with two different wall thicknesses (3 and 4 mm) and 10 different shell sizes (44- to 62-mm outer diameter) were implanted into eight cadavers. Shell deformation was then measured in the cadavers using a previously validated ATOS Triple Scan III optical system. The shell–bone interface was then considered as a spring system according to Hooke’s law and from this the force exerted on the shell by the bone was calculated using a combined stiffness consisting of the measured shell stiffness and a calculated bone stiffness. The median radial stiffness for the 3-mm wall thickness was 4192 N/mm (range, 2920–6257 N/mm), while for the 4-mm wall thickness the median was 9633 N/mm (range, 6875–14,341 N/mm). The median deformation was 48 µm (range, 3–187 µm), while the median force was 256 N (range, 26–916 N). No statistically significant correlation was found between shell stiffness and deformation. Deformation was also found to be not fully symmetric (centres 180° apart), with a median angle discrepancy of 11.5° between the two maximum positive points of deformation. Further work is still required to understand how the bone influences acetabular shell deformation.
Source: Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine - Category: Biomedical Engineering Authors: Tags: Original Articles Source Type: research