This project seeks to design innovative tools to measure in vivo biomechanical parameters of joint prostheses, orthopaedic implants, bones and ligaments. These tools, partly implanted, partly external, will record and analyze relevant information in order to improve medical treatments. An implant module includes sensors in order to measure the forces, temperature sensors to measure the interface frictions, magneto-resistance sensors to measure the 3D orientation of the knee joint as well as accelerometers to measure stem micro-motion and impacts. An external module, fixed on the patient.s body segments, includes electronic components to power and to communicate with the implant, as well as a set of sensors for measurements that can be realized externally. This equipment is designed to help the surgeon with the alignment or positioning phase during surgery. After surgery, by providing excessive wear and micro-motion information about the prosthesis, it will allow to detect any early migration and potentially avoid later failure. During rehabilitation, it will provide useful outcomes to evaluate in vivo joint function. The tools provided can also be implanted during any joint surgery in order to give the physician the information needed to diagnose future disease such as ligament insufficiency, osteoarthritis or prevent further accident. The proposed nanosystems are set to improve the efficiency of healthcare, which is both a benefit to the patient and to society. Although the scientific and technical developments proposed in this project can be applied to all orthopaedic implants, the technological platform which is being built as a demonstrator is limited to the case of knee prosthesis. In addition, by reaching the minimum size achievable thanks to clever packaging techniques and also by reducing, or even removing, the cumbersome battery, it paves the way for a new generation of autonomous implantable medical devices.

1. SImOS Smart Implants for Orthopedic Surgery Prof. Dr. Peter Ryser EPFL on behalf of SImOS partners

6. Introduction: the concept of the project Force & motion sensors Electronics Sensors interface Communication Packaging Biomechanical modeling Surgical implantation

8. Large-scale demonstrator architecture A smaller version of the demonstrator, acquiring the signals of the force sensors inside the polyethylene part of the prostheses, has been developed. Sensor Analog front-end Microcontroller Communication Power management Magnetometers HMC5843 I2C Accelerometers I2C/SPI Analog sensors Sensor Interface vdd2.7 vdd1.8 I2C Vdd1.8 vdd1.8 I2C/SPI vdd2.7 ip1 ip2 in1 in2 DISCRETE COMPONENTS CPLD PMU Power management unit MAX17710 vdd2.7 vdd1.8 MCU I2C and/or SPI SPI JTAG SPI MSP430 Serial memory JTAG Bridge For ISP CPLD JTAG Battery and/or supercap RF transponder TMS 37157 SPI

9. Remote Powering Best performance under the influence of the metallic parts. [Atasoy, Prime2010] Reader Antenna Implanted Antenna Image source: http://healthtopics.hcf.com.au/TotalKneeReplacement.aspx External coil circumferences the knee Internal coil inside the insert

10. Force sensors Si TiW Al PI Ti Pt Ti Strain gauge Fabrication Design Realization Specifications Excitation: 1.5V Power: 0.7mW Gauge factor: ~2 Volume: 0.24mm 2

11. Motion sensors d + (L) AMR sensors Magnet AMR sensors Artificial Neural Network  Reference sensor angle rms error during Rotation : 0.6 deg Translation : 0.8 deg Sensitive dist. range L=25mm L=8mm L=5mm d

15. First technology demonstrator