The laboratory’s involvement with total joint arthroplasty began with Dr. Ramon Gustilo’s             development of the Genesis I total knee system in the early 1980s. Various implants have             been developed and evaluated in conjunction with the laboratory over the years (see

History). More recently, the OBL was involved in the design and evaluation of a modular             acetabular cup implant that accounts for acetabular bony deficiencies.

Although it is commonplace for a patient to have excellent results with primary hip and             knee replacement surgery, the outcome of the revision of failed primary arthroplasties has             been significantly less successful. Because the number of revision procedures is expected             to increase in coming years, a major emphasis of joint replacement research is to improve             the outcome of revision arthroplasty.             NIH has funded work based on a productive collaboration with Dr. Kjeld Søballe from             Aarhus, Denmark, on revision surgery. Numerous studies have been conducted on             materials and methods to encourage the growth of bone and increase stability at the             implant/bone interface in the revision setting through the use of hydroxyapatite coating,             RGD peptide coating, bone graft, bone morphogenetic proteins, platelet concentrates with             autologous growth factors, bisphosphonates, and local perforation of the sclerotic             endosteal rim.             Wear is one of the main factors that limits the life of hip and knee replacements, and as             such, is another major emphasis of our joint replacement research. For example, we have             used finite element modeling and statistical design of experiments to study the effect of             design features of hip replacement acetabular components on articulating wear. A three–             dimensional radiographic technique was used to measure wear between total hip             arthroplasty components as function of the design and type of fixation (i.e., all–polyethylene             or metal–backed cups with cemented or cementless fixation).             In addition to the articulating surfaces, wear is also generated at the interfaces between the             components of modular implants, in particular between the backside of a polyethylene liner             and its metal backing. This backside wear is a result of the gradual loosening of the             modular locking mechanisms with repeated load over time. These wear particles, in             addition to the unavoidable articular wear, can lead to increased osteolysis, and subsequent             increased component loosening and failure.             To address this issue, stability of locking mechanisms in commercially available             metal–backed acetabular cups was determined as a function of the temperature and force             of insertion, and under long–term cyclic loading. The laboratory is developing innovative             second–generation locking mechanisms of polyethylene inserts to their metal backing             based on shape memory alloys. Finally, a study was conducted to determine the effect of             design features of Morse tapers on locking stability, wear and corrosion.             Adequate stability of the fixation of prosthetic components to bone must be obtained for a             successful outcome of joint replacement. In vitro studies were performed to determine the             stability of knee and hip replacement components as a function of various design and             physiologic factors such as short stems versus long stems, osteoporotic bone versus             normal dense bone, cemented versus uncemented fixation with packed allograft or             autograft, and revision versus primary replacement.             The OBL is responsible for developing the concept of preparing bony surfaces for hip and             knee replacement by compaction of existing cancellous bone, rather than removal of this             bone with a rasp. This concept has been evaluated on many fronts including the             measurement of in vitro stability of hip and knee components with compaction versus             broaching, optimization of surgical instruments to avoid intraoperative fracture with             compaction, micro–CT scanning of compacted in vivo bone, and clinical follow–up of             perioperative results with compaction (e.g., occurrence of fracture, blood loss, operative             time, length of stay).             Instrumentation systems needed for insertion of knee and hip arthroplasty components are             very complex and expensive, thereby limiting their use. In an attempt to increase the             availability of joint replacement, particularly in third-world countries and to less experienced             orthopedists, the laboratory developed simplified, inexpensive and accurate knee             instrumentation that allows precise preparation of bony surfaces to receive knee implant             components. Improved instrumentation for minimally invasive arthroplasty surgery is also             being developed.