Stress analysis of glenoid component designs for shoulder arthroplasty.

Secure and lasting fixation of the glenoid component in total shoulder arthroplasty is difficult because there is an insufficient volume of strong bone in the scapula. Consequently, radiolucencies of the glenoid component are common (much more common than radiolucencies of the humeral component). Early glenoid component designs were fabricated wholly from polyethylene, were fixated with PMMA cement, and had various degrees of constraint and conformity between the glenoid surface and the ball of the humeral component. More recent design variations include metal backing and non-cemented anchorage systems. In this study, various designs of cemented glenoid component are analysed using the finite element method. These are examined for (a) two different abduction angles; 60 degrees and 90 degrees; (b) high and low conformity and (c) high and low constraint. Stress distributions are compared with the failure strengths of the components and the influence of the various design factors can be observed.