Effect of the design parameters on the in vitro wear performance of total shoulder arthroplasties

The loosening of the glenoid component is the main reason for the failure of a total shoulder arthoplasty. It may be caused either by high tensile stresses or by osteolysis of the surrounding bone in response to the presence of particle debris. This failure might be associated with the wear of the implant as occurs with replacement hip and knee joints. per reports the findings of a study of the in vitro performance of the currently used total shoulder prostheses to determine the effects of implant geometry on the wear of the polyethylene components and the friction conditions operating within the shoulder prosthesis. ar performance of the implants was evaluated using a self-developed tribotester, simulating the physiological conditions of a shoulder joint. This study revealed that significantly different wear occurred with conforming and non-conforming articulation and revealed the influence of the thickness of the polyethylene glenoid on the wear and friction occurring in the joint. In this preliminary study significant wear of the polyethylene glenoid component occurred, estimated to be up to 19 mm3/year, which is similar to that found in retrieved implants. The conforming implants demonstrated significantly greater wear than the non-conforming implants (p < 0.05). A significantly lower friction factor, about 0.05 ± 0.01 (p < 0.05), was obtained for the less conforming implants.