Finite element modelling of rheological and penetration characteristics of curing PMMA bone cement in total hip replacement

This thesis is concerned with the study of the rheological properties of PMMA bone cement that is used as a grout for bone and prosthesis in THR and TKR Interdigitation of bone cement through porous cancellous bone depends on the rheological characteristics of bone cement and porosity of the cancellous bone. The rheological characteristics of the bone cement are thus an important factor effecting the optimum penetration of bone cement through cancellous bone. In this project the rheological properties of commercial bone cement were collected from other researchers and used in this study as the input for the finite element simulation (FIDAP simulation software) to determine the flow patterns and degree of penetration of the cement. The thermal properties of curing PMMA bone cement were measured using a standard mould at different vacuum pressures. The changes in the rheological properties with respect to time were used as the inputs to the finite element software. The maximum temperature of bone cement was found to decrease with increasing cement mixing vacuum level for pseudoplastic bone cements. Each of the bone cements investigated has a minimum setting time at maximum vacuum mixing. The average penetration increased by increasing the prosthesis insertion velocity for pseudoplastic bone cement. The maximum pressure developed in the bone cement can be decreased significantly for pseudoplastic bone cement by increasing the prosthesis insertion velocity. No significant difference was found in the bone cement penetration when the duration of applied pressure used prior to prosthesis insertion for cement was altered The increase in bone cement penetration was high for cement with pseudoplastic behaviour as the time of prosthesis insertion was increased from 05 minute to 15 minutes. The maximum pressure developed in the bone cement was found to decrease significantly for bone cement with pseudoplastic behaviour when the prosthesis insertion time was increased. For bone cements with pseudoplastic behaviour decreasing the amount of bone cement increases the penetration