Master of Engineering Science
Musculoskeletal Health Research
Teeter, Matthew G.
Robarts Research Institute
Holdsworth, David W.
Robarts Research Institute
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.
Summary for Lay Audience
Knee replacement surgeries are among the most commonly performed operation in North America. Generally, these procedures are quite successful but occasionally complications arise. Serious complications may require further surgery to rectify. Currently, the most common cause for additional “revision” surgeries is infection. Unfortunately, current solutions are unable to eliminate the infection in an alarming ~15% of cases, which may result in serious long-term mobility challenges, amputation or even death. The hypothesis suggests that the diagnostic tools being used are insufficient for determining infection status during treatment. This project outlines the development of a novel sensing package intended for seamless integration with the current North American standard treatment protocol, the “two-stage revision”. This implantable device will collect biometric (temperature) readings and store them for bulk wireless offloading to a physician’s mobile device for analysis. Future human trials will be used to hopefully find a correlation between infection and mean knee temperature during treatment.
This thesis outlines the entire design process including an evaluation of current tools, problem definition, concept generation/selection, implementation and design validation. During testing of this device, temperature sensing performance was evaluated using a custom-built, programmable temperature chamber in addition to a water bath. The device was then surgically installed in a cadaver knee to demonstrate appropriate sensing, telemetric and mechanical capabilities while in a simulated working environment.
The exciting test performance results of this device imply great optimism, not only for the success of the proposed project, but for sensing applications throughout the healthcare industry.
Lavdas, Michael K., "Development of an Active Infection Monitoring Knee Spacer for Two-Stage Revision" (2020). Electronic Thesis and Dissertation Repository. 7285.
Available for download on Thursday, July 21, 2022