Modular titanium alloy neck adapter failures in hip replacement--failure mode analysis and influence of implant material.

Background: Modular neck adapters for hip arthroplasty stems allow the surgeon to modify CCD angle, offset and femoral anteversion intraoperatively. Fretting or crevice corrosion may lead to failure of such a modular device due to high loads or surface contamination inside the modular coupling. Unfortunately we have experienced such a failure of implants and now report our clinical experience with the failures in order to advance orthopaedic material research and joint replacement surgery.

Fixed bearing knee congruency -- influence on contact mechanics, abrasive wear and kinematics.

The objective of our study was to evaluate the in vitro wear behavior of fixed bearing designs for total knee arthroplasty in relation to contact mechanics and resultant kinematics for different degrees of congruency. a finite element model was created for three knee articulations with increasing degrees of tibio-femoral congruency (flat, curved, and dished design). For the three different knee design configurations, in vitro wear simulation was performed according to iso 14243-1.