SBIR-STTR Award

Recent developments and experience in aerospace/engineering applications has established a clear superiority of layered composite zirconia/steel couples as ultra low wear. This has a great potential for implant applications in virtually eliminating wear particle mediated osteolysis and consequent implant failures. Wear rates comparable to ceramic/ceramic couples with demonstrated 2-3 orders lower wear volume than the best ceramic/PE couples can be expected. In contrast to the ceramic/ceramic couples however, the proposed composite ceramic/metal couple alleviates the major clinical concern stemming from brittle fracture. In a novel alternative approach to eliminating PE wear debris and lowering risk of brittle failure, a composite ceramic tibial component articulating against a Co-Cr femoral component is proposed. Developments and experience from the engineering fields is proposed to be applied to biomedical implant applications and is expected to lead to both superior wear resistance (comparable to the best ceramic/ceramic couples), with elimination of the PE tibial component. Toughness, enhancement of 2x over conventional ceramics significantly reduces risk of tibial failure. This is particularly relevant to mobile wearing knee designs where increased range of motion and resultant wear is observed. Phase 1 will establish the superior materials properties and demonstrate significantly reduced wear rates. In Phase 2, wear simulator tests will be conducted along with design and manufacturing process optimization. PROPOSED COMMERCIAL APPLICATION The novel combination of an ultra-tough composite ceramic tibial components articulating against Co-Cr femoral components will lead to negligible wear debris and implant failures. Adaptation and enhancement of an established engineering ceramic for articulation with the established Co-Cr condylar components will greatly enhance commercial applications.

Thesaurus Terms:
biomaterial development /preparation, biomaterial evaluation, ceramic, implant, knee, tibia, tissue engineering, zirconium biomaterial interface phenomena, biomechanics, cerium, composite resin, joint prosthesis, mechanical stress, skeletal stress, yttrium medical implant science, scanning electron microscopy

Mobile bearing TKA implants are preferred owing to their potential to better restore natural knee kinematics, and could find increased acceptance if the important clinical concern related to increased wear is addressed. Equally, overcoming the materials fatigue related failures of polyethlylene (PE) tibial inserts over the long term would be a significant step forward in extending the life, range of motion and function of the more popular fixed bearing TKA implants. In Phase I, we successfully demonstrated the feasibility of a novel, ultra-low wear bearing for TKA implants by developing and wear testing of a new ceramic optimized for low friction articulation against established CoCr alloys. The novel ceramic material was shown in standard tests to possess the highest combination of strength, toughness and Weibull modulus, with a significant enhancement over current state of the art Biolox Delta. We have also demonstrated in pin on disc tests a 10 fold reduction in multidirectional wear compared to CoCr-PE bearings, under a 3X higher contact stress. This success points to the clinical potential of a novel alternate TKA implant bearing with ultra-low wear and high safety characteristics: a CoCr femoral condyle/ with a ceramic tibia insert. If successful, this novel TKA bearing offers the potential to eliminate PE material failure and promises to increase the life of TKA implants by a factor of 2 - 3X. Indeed, this bearing has the potential to introduce a unique, safe and effective alternative bearing for the first time, for TKA implants. In Phase II, we aim to extend these results by developing and demonstrating the wear performance, mechanical and biological safety of actual TKA implant components in a physiologically / clinically more relevant geometry. In Phase II, we propose to extend these promising results by developing, optimizing and demonstrating in vitro, the wear performance, mechanical safety and function in a set of comprehensive, statistically rigorous experimental designs. We also propose to conduct wear tests to 10 million cycles in a knee simulator on actual TKA bearing components of both mobile and fixed bearing designs, using physiologically relevant test parameters, to confirm the superiority of the novel proposed bearings. Major orthopedic implant manufacturers have expressed interest in our technology and collaborating on the evaluation of the novel TKA bearings