Summary
Summary A transducer for measuring threedimensional segmental spinal motion was designed to directly measure dynamic rotations (Rx, Ry and Rz) about three orthogonal axes using an array of liquid metal strain gauges (LMSGs). The configuration of the LMSG array results in differential length changes due to segmental spinal motion. In vitro calibration utilized transducer attachment to Steinmann pins implanted into the dorsal spinous processes of anatomical spinal segments. The response of the LMSGs approximated linearity (R2 ≥0.980) over the calibrated ranges of angular displacement (i.e., ± 5°). On average, artifactual mechanical noise of the LMSGs was <3% of the signal recorded during locomotion. The minimum resolution of the transducer was 0.07 degrees of flexion-extension, 0.46 degrees of lateral bending, and 0.56 degrees of rotation. Average resistive force for all transducers was 0.31 ± 0.05 Nm at the neutral articular position (0°) and 0.51 ± 0.03 Nm at 5° of flexion. Clinically, the modest mechanical resistance of the transducers did not affect spinal mobility nor locomotion. In vivo application of the transducer was demonstrated at thoracolumbar and lumbosacral spinal segments in horses treadmill locomotion. The transducer was designed and tested on an equine model, but may be adapted for other quadrupeds. The dynamic and continuous measure of three-dimensional in vivo segmental spinal motion will provide an important new perspective for evaluating normal and altered spinal motion.
A technique was developed for directly measuring threedimensional segmental spinal motion in the thoracolumbar and lumbosacral spinal segments in horses during treadmill locomotion. The dynamic and continuous measure of three-dimensional in vivo segmental spinal motion will provide an important new perspective for evaluating normal and altered spinal motion associated with back problems.
Keywords
Kinematics - spine - liquid metal strain gauge - equine
