Automated Analysis of Lumbar Spine Kinematics from Dynamic Videofluoroscopy
We hypothesize that intervertebral kinematics during flexion and extension motion in the presence of lower back pain will differ from that measured during pain-free motion. Thus, we are attempting to measure the motion of individual lumbar vertebrae noninvasively from dynamic fluoroscopic sequences. 2D normalized mutual information-based image registration will be used to track frame-to-frame motion. In use, the operator identifies each vertebra to be tracked on the first frame of the sequence using a four-point "caliper" placed at the posterior and anterior edges of the inferior and superior end plates of the target vertebrae. The program then resolves the individual motions of each vertebra independently throughout the entire sequence (Figure 1).
Figure 1: Automated software for vertebral kinematics quantification. On the left, the vertebral body was located manually (shown in green) in frame 1. On the right, a subsequent frame is shown where the location of the vertebral body was determined using an automated registration technique.
To validate this technique, 5 cadaveric specimens including the sacrum and lumbar spine were instrumented with sensors from an optoelectric kinematic data acquisition system (Optotrak Certus, Northern Digital, Inc.). The specimens were potted in PMMA and placed in a custom dynamic spine simulator and moved through flexion-extension cycles while three-dimensional kinematic and fluoroscopic sequences were simultaneously acquired. We found strong correlation between the absolute flexion-extension range of motion of each vertebra as recorded by the Optotrak and as determined from the VF sequence via registration, and conclude that this method is a viable way of noninvasively assessing 2D vertebral motion.
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