EFFECT OF TAPERED GEOMETRY ON THE LOAD TRANSFER OF AN IDEALIZED CEMENTED HIP IMPLANT

摘要

Implant loosening of cemented hip implants is one of the major causes of failure of the arthroplasty. In cemented hip implants, the polymethyl methacrylate (PMMA), also called bone cement, is used as grouting material between the stem and the surrounding bone. During polymerisation of the cement, residual stresses are generated in the bulk cement. The bone cement does not have a chemical bond with the stem nor the bone; however, it fills completely the space between the two and serves to distribute the load being transferred from the stem to the bone. Numerical analyses on the load transfer of cemented hip implants usually do not include the residual stresses due to cement curing at the stem-cement interface. A recent study has shown that the inclusion of the residual stresses at the stem-cement interface affected the load transfer for an early post-operative situation. Their finite element (FE) analysis was performed on an idealized cemented hip implant having a straight stem. This study investigated the load transfer of an idealized cemented hip implant of tapered geometry. The FE analysis was three-dimensional and used non-linear contact elements to represent the debonded stem-cement interface. The cement stress distributions were determined at the interface with the inclusion of the residual stresses.