In vitro and finite element analysis of glenoid bone/baseplate interaction in the reverse shoulder design.

We developed biomechanical and finite element models, using high-strength polyurethane foam blocks, to represent the glenoid bone/baseplate junction to determine if increasing the distance between the glenoid bone and the center of rotation of the glenosphere increases baseplate motion during static loading in the reverse shoulder design. Although there was a general trend toward increased baseplate motion with increasing distance from the glenoid to the center of rotation, in vitro mechanical testing revealed no significant difference between the 7 glenosphere types tested, with average baseplate motion during 1000 load cycles ranging from 90 mum to 120 mum. Results from the finite element analysis strongly correlated with the in vitro mechanical testing. The magnitude of baseplate motion occurring in a modeled representation of bone under simulated physiologic loading conditions was similar for the 7 reverse shoulder glenoid components tested in this study.