I-Corps: Ligament Tension Sensor

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is the development of a device to measure the tension in ligaments. Ligaments are tissues that connect bones together at joints and help guide the motion of the joint. Despite the critical importance of understanding ligament tension for a wide range of clinical applications (e.g., ligament repair and total knee replacement), there are no devices to directly and non-invasively measure ligament tension in vivo. Measuring ligament tension using the proposed device may help surgeons to better personalize treatments, which may reduce the need for costly follow-up procedures to correct improperly tensioned ligaments that often cause pain, stiffness, and/or instability. In addition, the proposed device may be used as a diagnostic and pre-operative planning tool as well as in orthopedic and rehabilitation clinics. This I-Corps project is based on the development of a device to determine ligament tension based on the propagation speed of shear waves in the ligament. This phenomenon is similar to the variation in a guitar string’s vibration frequency with tension (i.e., a tighter string has a higher shear wave speed and frequency). Alternative technologies (e.g., buckle transducers and optical fibers) measure ligament tension, but require invasive implantations preventing their translation into the clinic. The proposed sensor technology, called a ligament tensiometer, is placed against the skin superficial to the ligament of interest and the device excites a shear wave and tracks its propagation through the skin and subcutaneous tissues. It has been shown that the speed that the wave travels along the ligament accurately predicts the tension in the ligament. The proposed initial target application is total knee arthroplasty because the technology may enable surgeons to identify and correct individual structures that may be improperly tensioned, which could mitigate post-operative pain, stiffness, and instability. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.