052 IN VITRO BIOMECHANIC EVALUATION OF CEMENT-IN-CEMENT INTERFACE IN HIP ARTHROPLASTY REVISIONS

In selected patients in-cement revision of the total hip arthroplasty components is an attractive option. Recommended roughening of the primary mantle surface remains controversial. Aim of the study was to investigate the influence of the cement surface roughening on the strength of bilaminar cement interface. Flat, laboratory model of bilaminar cement interface was used. Prior to its creation, modeled primary mantle surface was machined to the roughness of either smooth surface observed after removal of a highly polished stem (Ra=200nm) or that following roughening (Ra=5μm). Two viscosities of interfering fluids (water and bone marrow) were also used. 6 variants (smooth or rough, both stained with water, bone marrow or with no fluid) with 7 repeats were exposed to single shear to failure. No significant difference in resistance to shear was observed between the groups with dry smooth (16.82MPa) and rough surfaces (16.96MPa), and those stained with large volume of low viscosity fluid. In the presence of water, roughening did not significantly influence the interface (smooth – 17.04MPa and rough – 16.25MPa respectively). In the smooth variant with large volume of viscous fluid, ultimate stress value dropped to 5.53MPa, and 9.87MPa in the roughened group with the same amount of viscous fluid (p Extra roughening may offer some benefit when performing in-cement revision in the presence of large volume of viscous fluid only though in-cement revision would not be then recommended. In the presence of low viscosity fluids (blood, irrigation fluid) benefit of roughening is dubious.