Evaluation of the glenoid implant survival using a biomechanical finite element analysis: influence of the implant design, bone properties, and loading location.

Total shoulder arthroplasty has become a successful surgical procedure through design improvements. However, lucent lines around the glenoid component are of major concern for leading to component loosening. To better understand the mechanism causing loosening, a finite element biomechanical model of an in vivo scapula was developed. The effect of eccentric loading was analyzed on a keel glenoid and a peg glenoid implant. Results indicated that eccentric loading greatly increases stresses in the cement mantle at the bone-cement interface, and no significant difference was predicted between keel and peg implants. The results suggested that eccentric loading is a likely cause for initiation of cracks in the cement layer especially on the posterior side. Moreover, these results, compared with other studies, indicate that geometric and bone properties of the scapula may be more important factors in the success of shoulder arthroplasty than implant design.