The study of joint contact mechanics to better understanding of all processes leading to cartilage degradation is very necessary. Elbow replacement will be the only option if both inner and outer components of the elbow have severe arthritis, or usually rheumatoid arthritis. It may also be recommended if there is osteoarthritis which makes the elbow stiff and painful, or a severe fracture of the elbow. Recently the operation known as Lateral resurfacing elbow replacement has been developed and introduced in hospitals. This operation has been designed for those people whose disease in the elbow involves mainly the outer compartment of the joint. The components are made from the metal and polyethylene and are fixed to the bones. An improper design of implants can lead to toxicity for patients caused by excessive amount of metal debris.
The purpose of this paper is to investigate the effect of roughness in Lateral resurfacing elbow implants. This paper develops a contact model to treat the interaction of the new surfaces fixed to the top of radius and humeral. The contact model describes the interaction of implant rough surfaces including both elastic and plastic deformations. In the model, surfaces are investigated as macroscopically conforming semi-spheres containing micron-scale roughness. The derived equations relate contact force on the implant and the minimum mean surface separation of the rough surfaces. Based on the distribution of asperity heights, the force is expressed using statistical integral function of asperity heights over the possible region of interaction of the roughness of the implant surfaces. Closed-form approximate equation relating contact force and minimum separation is used to obtain energy loss per cycle in a load-unload sequence applied to the implant.
