A Wireless, Battery-Free Embedded Sensor for Monitoring Tension on a Suture Anchor

Abstract

A passively powered wireless sensor based on an inductive-capacitive-resistive (LCR) sensor was developed to measure tensile stress at suture anchors used to repair soft tissue injuries such as ligament and tendon tears. The sensor, which is completely embedded within the suture anchor, consists of a strain gauge mounted on a substrate with a loop connector so a suture can pass through. When the suture experiences a tensile stress, it pulls at the loop connector and the strain gauge, allowing measurement of tensile stress at the suture. In this study, sensors of different designs were fabricated and characterized ex vivo to determine their force sensing capabilities. The effects of sensor placement and orientation on accuracy were also characterized. The LCR suture anchor sensor can be used to assess the quality of soft tissue treatments, such as rotator cuff repairs, as well as to detect failure of the implant post-surgery. The advantages of this sensor are its small size, wireless detection, and battery-free operation, making it ideal for use with both short- and long-term implants.