An implantable system for the in vivo measurement of Hip and Knee migration and micromotion

This paper describes an implantable system for the in vivo measurement of both micromotion and migration in applications such as total hip arthroplasty (THA) and total knee arthroplasty (TKA). The system is based on a modified linear variable differential transformer (LVDT) whose null-point is set automatically by a self-calibration algorithm. The self-calibration process not only allows the measuring bridge to work at maximum accuracy (i.e. for micromotion measurements but also automatically records gross changes in position (migration).