Browsing by keyword "*Bone Cements"
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Early cementing does not increase debond energy of grit blasted interfacesA fracture mechanics based approach was used to determine the debond energy or fracture toughness of the stem-cement interface for a variety of conditions. The goals of the study were to determine if early cementing of stems increased the debond energy of grit blasted stem-cement interfaces and if debond energy was dependent on mold type. Early (2 min) and late (6 min) times of cementation were considered for two different grit blasted surface finishes (16 and 60 grit, Ra=5.7 or 2.3 microm). Specimen fabrication was performed using a relatively simple, unconstrained rectangular mold and a mold that more closely simulated in vivo conditions. The rectangular mold was used with all components at room temperature whereas the in vivo simulated mold had a body that resembled the femoral canal in shape and was warmed to body temperature. Early cementing did not increase the debond energy using the in vivo simulated mold. Extensive porosity was found at the interface, and porosity had a strong negative effect on debond energy. When the simpler, rectangular mold was used, early cementing did result in higher debond energies, but few voids were found at the interface. It appears that porosity at the interface was the major factor affecting the debond energy. The results from this study do not support the concept that improved stem-cement interface strength can be obtained by application of the cement while it is in a low viscosity state.
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The importance of proximal cement filling of the calcar region: a biomechanical justificationClinical studies have suggested that a thicker proximal medial cement mantle improves the long-term outcomes of cemented femoral components. A 3-dimensional finite element model was used to determine the effect that replacement of proximal medial trabecular bone with cement has on cement mantle stresses. With removal of cancellous bone in the calcar region, there was a decrease in peak cement mantle stresses by approximately 20%. The greatest reduction in cement mantle stress was seen after cancellous bone was removed from the proximal medial aspect of the femur to a distance 30 mm distal to the femoral neck resection. Under fatigue loading conditions simulating gait, removal of proximal medial cancellous bone could increase the number of loading cycles to failure by a factor of 3.5. These results support the removal of proximal medial cancellous bone from the calcar region intraoperatively to increase the cement mantle thickness and reduce cement mantle stresses to improve the long-term fixation of cemented femoral components.