Optimized Prototype of Instrumented Knee Implant: Experimental Validation

Abstract Background: Embedding self-powered sensors into the knee implant for measuring in-vivo tibiofemoral force distribution can provide beneficial information to both clinicians and researchers. This information may help to reduce the risk of early failure after total knee arthroplasty. It can also be used to improve implant design, refine surgical techniques and enhance postoperative rehabilitation. Methods: An experimental prototype of instrumented tibial baseplate has previously been proposed, developed and tested. A few shortcomings have been observed and identified during the experimental testing. In this study, the design of the proposed prototype was optimized to avoid the mechanical failure of the embedded piezoelectric generator/sensor. Furthermore, piezoceramics of greater height and smaller section were accommodated and tested in the optimized prototype to generate more electric power. This optimized prototype was also experimentally tested using a knee simulator to validate the optimization result. Results: The optimization made to the experimental prototype allowed us to address the aforementioned shortcomings. The mechanical longevity of piezoceramics embedded into the optimized prototype was considerably enhanced with respect to the first prototype (optimized prototype: 54000 gait cycles, first prototype: a few cycles). The produced electric power was also increased (optimized prototype: 4.28 mW, first prototype: 1.81 mW). Conclusion: The optimized prototype lasted for 54000 gait cycles without any obvious mechanical or electrical failures. The electric power produced in this prototype and quantified during experimental trials is sufficient to power an efficient low-power-consumption telemetry system.