SBIR Phase II: A New Vibration Mixer for Bone Cement

Clinical And Industrial Technology Co, Seneca SC

Investigators

Abstract

This SBIR Phase II project is aimed at developing a novel vibration mixer for the mixing of surgical grade bone cement. Self-curing polymethylmethacrylate (PMMA) or acrylic bone cement is used extensively in total joint replacements, in the repair of bony defects and in the fixation of pathological fractures. For surgical use, the methylmethacrylate polymer and the liquid monomer are hand mixed. This hand-mixing entraps air bubbles making the cement porous. Presence of these bubbles adversely affects the mechanical properties of bone cement, making it much weaker under load and may contribute to early failure of cemented artificial joints. Results of the Phase I study indicate that ultrasonic vibration during cement mixing significantly reduced its porosity and increased the fatigue life and mechanical strength of bone cement, compared to hand-mixed cement. Recently, it was shown that combining sonication and vacuum mixing reduced the porosity and further improved the fatigue life, compared to either mixing methods alone. During the Phase II study, the frequency and amplitude of sonication and the vacuum pressure to obtain the best mechanical properties of the cement will be optimized. Subsequently, a new cement mixer will be designed and built incorporating these mixing features. It is expected that the improved mechanical properties of vibrated bone cement will reduce the incidence of cement fracture and this will improve the success rate of total joint replacements. Considering that cement mixers are used in several thousand hospitals in the United States alone, we expect this new cement mixer to be adopted by a large number of Orthopaedic surgeons in these hospitals.