AbstractA Swiss research laboratory is developing a new concept for in vivo monitoring of metallic implants by electrochemical techniques. A prototype system consisting of implanted sensors and electronics combined to hip or knee prostheses, as well as a telemetry device, allows the measurement of implant’s function and degradation during its life span. Abnormal wear or corrosion of the implant can be detected. The laboratory is looking for license agreement and further development partnership.
DetailsMetallic implants in living tissues are subject to the corrosive environment of body fluids. The biomaterials are selected for their corrosion resistance in order to avoid contamination of the surrounding tissues by corrosion products such as metallic ions. This resistance to corrosion is usually achieved by the spontaneous formation of a protective surface oxide film which shields the metal from the environment. If relative motion takes place between the implant and the surrounding tissues, the surface film may be damaged. Uniform corrosion of metallic materials may take place due to inflammation of the surrounding tissues, which leads to a change of pH.
Electrochemical techniques allow the monitoring of such events with high sensitivity thus providing a means to assess the surface condition of the implant. Additionally, it is possible to obtain local information and thus identify the source of the problem.
The monitoring system, developed by the Swiss research laboratory, consists of a secondary implantable electronic device. The latter includes measurement sensors, a signal processor, a communication subsystem composed of a Radio Frequency front-end and its antenna which allows the wireless external downloading of the measured data. Such a device can be constructed to be completely passive, i.e. without internal battery, which will avoid limitations of life span.
This technology is presently being assessed in knee prostheses in order to measure in vivo biomechanical parameters.
Implantable measuring devices which are powerful enough for electrochemical testing and passive wireless interface for the communication with the external reader already exist. The electrochemical techniques to be used are well understood in vitro. The challenge and the innovative aspect of this technology are to combine the two. Another challenge is to properly calibrate the electrochemical sensors (electrodes) and to optimize their use in living tissue.