Development of an Active Infection Monitoring Knee Spacer for Two-Stage Revision
Abstract
Infections requiring surgical revision occur in ~3% of total knee arthroplasty (TKA) procedures. The standard treatment for TKA infection in North America is referred to as the two-stage revision process. Unfortunately, the success rate of the two-stage revision is low, at roughly 85%. There are indications that the two-stage revision may fail to clear the infection due to unsatisfactory diagnostic tools. This thesis depicts the development and evaluation of a novel telemetric sensing package designed for integration into the two-stage revision process. Studies within evaluate its performance through sensor validation, thermal insulation testing, radio frequency penetration evaluation, a cadaveric loading study to confirm durability, a micro CT evaluation of the sensor’s impact on implant integrity and a comparison of internal vs external joint temperature during joint movement.
The results of this work describe a largely effective implantable tool for measuring, logging and transmitting diagnostic information about orthopaedic infection. Accuracy and precision of the sensing package were found to be ± 0.24°C and 0.09°C respectively with negligible hysteresis. Thermal insulation caused by the implant itself was found to produce a thermal time constant of 262.67 ± 4.56 seconds, which results in a very manageable ~17 minute rise time. Bluetooth stability was suitable for data and instruction transmission to both iOS and Android devices while the implant was in situ. Following cyclic loading of the cadaveric specimen with the instrumented implants installed, imaging and debridement revealed no obvious issues related to mechanical integrity of the bone cement spacer. However, some bone cement integration issues were observed. Although some engineering iteration and further testing is required, this research contributes a feasible proof-of-concept platform technology for ongoing investigation in orthopaedic infection and implantable telemetrics.