Mobility, stability and stress in artificial knees. A comparative study of nine prostheses representative of the condylar surface replacement type

The objective of this paper is to assess a representative number of the wide variety of condylar prostheses, on three accounts, all of which are consequences of the geometry. These are: 1. the range of flexion possible; being a limitng factor on the activities of the patient; 2. the amount of mechanical constraint on the prosthesis. This affects the stability of the joint in which the prosthesis is implanted. Furthermore, it is an extremely important factor in determining the long term soundness of the fixation of the components to the bone ends; 3. the contact areas and stresses arising in the prosthesis; since these are related to the life of the implant. The above mentioned assessment must be made, bearing in mind the difficulties met by and the limitations imposed on the designer. In order to appreciate these better the relevant design requirements and associated problems are discussed referring to the natural knee both as a starting point and guide. 12 refs.