Successful replacement of articular cartilage in the knee by a synthetic implant can help provide an alternative means of treating both osteoarthritis and rheumatoid arthritis as well as offer an alternative to total joint replacement for younger patients suffering from severe cartilage injury.
Synthesis and implementation of such a substitute must consider not only bulk material properties, but structure and interfacial physiology as well. Most implant-bone interface studies to date have been either intermedullary in nature, involved primarily cortical bone, or concerned integration with the periosteal membrane.
This study will instead focus on fixation of the implant directly to the condylar and tibial plateau cancellous bone surfaces. As opposed to the multiple-material composites that comprise traditional articular replacements, this study will investigate an implant constructed entirely of a single polymeric material selected to approximate the native properties of cartilage.
Fixation of this polymer articular cartilage replacement through a combination of mechanical and adhesive bonding approaches will be evaluated in three phases. First, the methods of mechanical and adhesive fixation will be designed and evaluated via benchtop testing using a two-dimensional approximation of the three-dimensional polymer/bone interface region.
Next, the mechanical and adhesive fixation techniques will be integrated and validated under physiological loading conditions, again using the two dimensional approximation. By defining critical parameters by which to judge the effectiveness of the fixation methods, refinements will be made and re-tested. In addition, the implant-bone interface will be analyzed using microscopy methods post-testing.
Fixation design will be altered as necessary until the target performance criteria are met or deemed unreachable for the specific materials investigated. If all design criteria are successfully met during the benchtop validation phase, then the effectiveness of the fixation technique will be evaluated in a true physiologic, three-dimensional loading environment using an in vivo test. The interface will then be examined and histologically characterized in order to evaluate general effectiveness of the final fixation design.