Biotribological engineering design for upper limb arthroplasty

点击翻译按钮获取中文摘要

Hip joint replacement implants have achieved low wear using crosslinked polyethylene (XLPE) as a bearing material. The previously significant clinical problem of wear particles causing bone death, implant loosening and revision surgeries that occurred with non-XLPE has been essentially eliminated. Also, in knee arthroplasty, more than half of the new procedures use implants with XLPE.***In upper limb arthroplasty, the increasingly popular reverse total shoulder arthroplasty (RTSA) is often used to treat severe osteoarthritis. It reverses the natural shoulder geometry and may use non-XLPE as a bearing material. Some laboratory testing has suggested that wear rates can be much reduced by using XLPE but other problems occur that tend to obscure any wear causation in the reported clinical failures. Thus, the need for XLPE remains uncertain.***To address the above issues, an existing simulator test machine will subject a number of RTSA implants to conditions as close as possible to those occurring in the body. A comparison of XLPE with non-XLPE wear rates is proposed that would correspond to their performance for the first few years in the body. Then, the influences of various implant design parameters will be investigated. The intent is to use these findings to engineer the design of RTSA implants to reduce wear and thus the clinical failure rates.***Another increasingly popular upper limb procedure (often needed after elbow fractures) is radial head hemiarthroplasty (RHH). It involves replacing only the radial surface of the elbow with a metal component which then slides against the opposing natural joint surface. The problem that arises here is one of progressive wear and damage to the natural joint surface that causes clinical failure and requires revision surgery.***A possible solution is to use a compliant, less damaging material for the implant surface. This is known to improve lubrication and reduce contact stress but the long term fatigue of the compliant material surface must be investigated to determine whether it will survive in the body. It is proposed to subject a number of specimens of an elastomeric material known as Bionate to surface fatigue. Once the surface fatigue has been explored, an improved design for RHH may be possible. Some current laboratory testing against natural surfaces will also be continued to ensure that the Bionate surfaces do not cause them overt harm and, of course, eventually clinical trials would be needed but they are not part of this proposal.***Thus, the proposed research program involves two projects of considerable scope that have the commonality that they both involve upper limb joint replacement and attempt to engineer the implant designs to reduce clinical failure rates.