Computer model analysis of the Swanson and sutter metacarpophalangeal joint implants

A representative model which mimics the behaviour of Silastic (R) finger me tacarpophalangeal joint implants was constructed using a finite element sof tware package. The modelled implants were moved through a range of flexion, lateral deviation and a combination of both. Pistoning of both implants st ems occurred within the modelled medullary cavities, For equivalent flexion angles, the Sutter implant produced a higher stress field than the Swanson implant, and the field was positioned at the central hinge mechanism. In b oth implants, lateral deviation increased the internal stress concentration s more than when pure flexion was applied. Overall the Swanson style of imp lant had lower stress magnitudes than the Sutter implant, and it is predict ed that the Sutter implant will be more likely to fail than the Swanson, Th e failure mode for the Sutter implant mould be at the central hinge region. The Swanson implant is likely to fail at the central hinge-stem interface regions.