Total hip replacement is a very successful orthopaedic procedure for patients with disabling joint diseases. However, it is common for these implants to last for only l0-15 years before revision surgery is required. The major long term complication in total hip arthroplasty is aseptic loosening which has largely been attributed to wear of prostheses. Vy'ear particles emanating from any of the interfaces of the replacement system are known to interact with the tissues surrounding replacements causing an adverse tissue response and eventual loosening of the implant. Of particular concern is the amount of wear debris produced at the articulation of the femoral head and acetabular component. The aim of this thesis is to produce a new design of artificial hip prosthesis that addresses the problem of wear particles and subsequent loosening. Prior to designing a new replacement system an extensive historical review of hip replacement was undertaken. In addition the mechanisms, determinants and biological implications of wear have been examined. The anatomy and biomechanics of the hip joint were considered and current materials and their biocompatability assessed for possible use in this design. All of these subjects were analysed critically prior to design and development of a new system. A sealed modular hip replacement system has been designed and developed in this thesis. The joint is sealed with a polymer sleeve that attaches near the periphery of the acetabular insert and a flange on the modular femoral head. These components combine to form a sealed bearing which would be delivered sterile from manufacture, ready for implantation at the time The Design of a Sealed Artificial Hip Replacement of surgery. A sealed joint ensures that wear particles cannot escape to the surrounding tissues and also prevents debris from entering the articulation and causing third body wear The sealing membrane traps all wear particles produced at the articulating surface within the sealed joint and it is proposed that a wear particle collection chamber is employed to collect them. The use of a ceramic or other porous material in which particles can lodge will reduce second body wear of the joint surfaces. As some of the designs developed in this thesis are novel concepts with commercial potential, a provisional patent has been filed. A preliminary marketing exercise has also been undertaken with a major implant manufacturer The author believes that this novel design of hip replacement system has the potential to increase the survival of hip replacement systems by the elimination of a major long term failure mode of aseptic loosening caused by wear particlesThesis (M.Med.Sc.)-- University of Adelaide, Dept. of Orthopaedics and Trauma, 199
