Finite element models (FEMs) generated from pre-operative computed tomography images of seven male patients with type A1 osteoarthritis were compared with simulated polyurethane (PU) foam block FEMs to evaluate normal and tangential micromotions during initial fixation of an all-polyethylene central pegged glenoid component. Models incorporated three commonly used PU foam stiffnesses and assessed micromotion between the implant backside and virtually reamed glenoid surface. Of 36 PU foam simulations, 10 demonstrated tangential micromotions and 15 demonstrated normal micromotions outside the interquartile range of osteoarthritic bone FEMs. These findings suggest standardized PU foam models may inadequately replicate osteoarthritic glenoid mechanics and should be used cautiously when evaluating glenoid implant micromotion.
Knowles et al. (Tue,) studied this question.