The Solution

OrthoDx has developed a wireless sensor system to monitor the stability of surgically placed orthopaedic implants utilizing near field inductive technology. Using this technique accurate implant motion detection is achievable within 50 microns (0.050 millimeters). Direct motion determination is performed in real time with no need for x-ray studies.

The system consists of two components: a wireless micromotion sensor coil(s) and a wireless communication module (WCM). The sensor coil is placed within the patient at time of surgery and is rigidly fixed to surrounding bone. It is placed close to, but not in contact with, a conductive prosthesis or implant. Placing the sensor in proximity to the prosthesis obviates the need for any modification of the prosthesis. The coil senses the distance, measured in microns, between itself and the target prosthesis, and communicates this data wirelessly to the WCM. The WCM, located outside the body, processes and stores the sensor data. Stability of the prosthesis is determined by sequential real time measurements which can be quickly and easily performed within an office setting at very low cost.

As an example, after total hip replacement, femoral micro motion can be dynamically collected during gait analysis, thus allowing precise implant motion monitoring throughout its’ lifetime.

This information will be readily available in the Cloud.

We have begun development of this patent pending system (US 15/805,726). To date, using bench techniques, we have been able to detect micron-scale displacements at practical target/sensor distances, and have performed simulations of sensor properties in a biological environment.

General view of the Hip Loosening Detection Using Inductive Proximity sensor.

A functioning prototype has been completed. Further cadaver and animal studies are pending.

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