Remote knee endoprosthesis monitoring – alignment requirements and prototyping of the external readout unit

Abstract

Knee arthroplasty follow-up involves only a limited number of X-ray-based implant condition assessments at extended intervals. Polyethylene (PE) wear of knee endoprosthesis often progresses unnoticed until symptomatic adverse effects become apparent or implant failure occurs. A PE wear measuring concept, consisting of an implanted passive sensor and an extracorporeal readout unit, was previously presented by our group. This system is intended to enable patients to regularly check their knee implants’ condition at home. In this context, an appropriate product design for the readout unit is essential to enable the user to record correct measurements. An experimental investigation of the optimized positioning of the system's readout unit was conducted and the measurement data were analyzed. The findings were then implemented in a prototype for readout unit attachment. A sleeve with Velcro and a sewn-in readout unit has been fabricated. A cutout for the patella ensures intuitive correct alignment of the measurement system according to the experimental results. A hardware housing incorporates the electronics.

Keywords

• knee
• prostheses
• implant
• monitoring
• arthroplasty
• sensor