The Curing and Pressurisation Behaviour of Bone Cement During Acetabular Cup Implantation in Cemented Hip Replacements

Abstract

Total hip replacement is the second most frequently performed arthroplasty surgery in the UK according to the National Joint Registry. It consists of resection of damaged bone and cartilage and implantation of an artificial acetabular cup and femoral head. These components are commonly fixed to the bone using polymethyl methacrylate (PMMA) bone cement which acts as a grout. A strong interface between the bone cement and bone relies on close mechanical interlocking. To achieve this, a load is applied to the cement to force it into the porous trabecular bone. The implant is then inserted into the pressurised cement and a load is applied to the acetabular cup until it is correctly positioned. The work that follows in this thesis was based on the hypothesis that the pressure achieved during surgery at the bone cement-acetabulum interface is suboptimal and may contribute to the development of radiolucent lines and therefore, early loosening. It was also hypothesised that, as PMMA bone cement is a polymerising plastic, the application of deformation whilst it is setting may result in the generation of residual stresses, weakening the cement. The results confirmed the initial hypotheses and hence provided evidence for the requirement of a new surgical device. A new device was designed, manufactured, and tested. It was found that it performed better than the device currently in use. A patent has been filed and work is planned to further validate the novel cementing device.