Telemetry system for monitoring anterior cruciate ligament graft forces in vivo

Eric Lynn McKee; Maury L. Hull; Stephen M. Howell

doi:10.1117/12.267118

14 February 1997 Telemetry system for monitoring anterior cruciate ligament graft forces in vivo

Eric Lynn McKee, Maury L. Hull, Stephen M. Howell

Proceedings Volume 3040, Smart Structures and Materials 1997: Smart Materials Technologies; (1997) https://doi.org/10.1117/12.267118
Event: Smart Structures and Materials '97, 1997, San Diego, CA, United States

Abstract

Quantifying changes in the tension of an anterior cruciate ligament (ACL) graft in vivo during rehabilitative exercises is vital for developing the optimal rehabilitation for patients who have had reconstructive surgery. The purpose of this project was to design, built, and test a telemetry system that can measure the in vivo ACL graft tension postoperatively. A commercially available fixation device was modified to sense the graft tension, house electronic components, transmit an output signal, and pass the power generating signal. A transcutaneous inductive link was used to power the implanted telemetry electronics. The current difference technique was used to measure changes in two strain gages that monitored shear strain developed on the femoral fixation device by the ACL graft. This current regulated a frequency modulated output signal and transmitted it, by using the ionic properties of body tissue as the medium, to external EMG surface electrodes. A signal conditioning board detected and converted the output to an analog voltage for collection by a computer data acquisition system. A performance evaluation demonstrated that the telemetry system either met or exceeded al of the criteria necessary for the application.

Citation Download Citation

Eric Lynn McKee, Maury L. Hull, and Stephen M. Howell "Telemetry system for monitoring anterior cruciate ligament graft forces in vivo", Proc. SPIE 3040, Smart Structures and Materials 1997: Smart Materials Technologies, (14 February 1997); https://doi.org/10.1117/12.267118

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