Wireless Suture Button Accessory Sensor for Intra- and Post-Operative Monitoring of Suture Loading in Soft Tissue Reconstruction

Background Tensioning and relaxation of grafts in tendon and ligament reconstruction surgeries significantly influence operation success, yet there are no clinically available technologies that can effectively measure both graft tension intra-operatively and during post-surgical recovery and rehabilitation. Objective To address the lack of an effective technology to measure graft tension intra-operatively and post-operatively, an implantable sensor was developed to provide real-time suture loading biofeedback both during reconstruction for surgeons and during rehabilitation exercises for physical therapists. Methods This paper introduces a passively powered wireless sensor designed to monitor tension of tendon and ligament sutures fixed in orthopedic reconstruction surgeries. The inductive-capacitive-resistive (LCR) based sensor was designed to be used along with commercially available suture buttons to monitor loading in reconstructed tendons and ligaments. Results Sensor loading experiments demonstrated a detection range from 5 N to 180 N with high repeatability (1.8 % change in sensitivity over 10,000 cycles). Additionally, the effects of depth, alignment, and orientation on signal transmission between the implantable sensor and an external detection device were characterized. Finally, the sensor was deployed in an anterior cruciate ligament reconstructed cadaver knee and used to detect graft loading during various knee joint movements. Conclusion This study established the design and basic functionality of a suture button accessory loading sensor to potentially assist orthopedic surgeons with surgical technique and help physical therapists with optimizing rehabilitation protocols for enhanced recovery in an effort to reduce failure rates.