Low-power SoC design for ligament balance measuring system in total knee arthroplasty

A design of a low-power wireless System-on-Chip (SoC) for the Ligament Balance Measuring System (LBMS) in Total Knee Arthroplasty (TKA) is presented in this paper. It includes a signal conditioning circuit that can support up to 15 force sensors, a 433 MHz RF front-end for data transmission, an 8-bit low-power microprocessor, and a FIFO with a digital filter. Idle and wake-up modes are well designed to reduce the power consumption since the device should be used for the whole surgical procedure. Test results show that the signal conditioning circuit with 16-bit single line output can operate under a wide voltage range, which is from 1.2V to 3.6V. The minimal power consumption is 139μ.W@1.2V with a 200 KHz clock. Experimental results demonstrated in static and body tests are given in the paper also. The chip will be used in an aided monitoring system for Total Knee Arthroplasty in the future work.