BME Seminar Series: Orhun K. Muratoglu, Ph.D.
Co-Director, Harris Orthopaedics Laboratory, Massachusetts General Hospital
Total joint (hip and knee) arthroplasty for end-stage joint diseases most commonly involves a metal/polymer articular pair. Ultrahigh molecular weight polyethylene (UHMWPE) has been and remains the material of choice for the load-bearing, articulating surface for this articular pair. Despite high long-term success rates for such reconstructions, wear and fatigue damage of polyethylene limit the longevity of total joints. Adhesive/abrasive wear is the primary source of particulate debris leading to peri-prosthetic osteolysis, the primary cause of failure in total hips. In total knees, implant failure is caused primarily by fatigue damage to the polyethylene components.
One of the solutions that we developed to reduce wear and osteolysis in total hips is radiation crosslinking followed by melting. Crosslinking reduces polyethylene wear and subsequent melting eliminates the residual free radicals ensuring long-term oxidative stability. This technology has been in clinical use for over a decade and has been implanted in over 3M patients worldwide. This talk will detail laboratory and clinical findings with this technology. Post-irradiation melting reduces the fatigue strength of polyethylene, limiting its use in young and active patients and total knees where the components are subjected to high-stress cyclic loading. Another method that we developed involves diffusion of α-tocopherol (vitamin-E) into irradiated polyethylene or warm-irradiation of vit-E/polyethylene blends. Vit-E stabilized crosslinked polyethylenes not only have improved wear, oxidation, and fatigue strength but they also exhibit reduced functional biological activity in particulate form.