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herniated discs, ultrasound, texture correlation, kinematics, vertebrae


Herniated discs in the spine are a significant patient burden, with potential links to lower back and leg discomfort and a considerable impact on daily life. These discs, located between spinal vertebrae, are comprised of the annulus fibrosus (AF) and the nucleus pulposus (NP). Herniations happen when the NP protrudes through a full-thickness annular tear, possibly compressing spinal nerves. The mechanical factors underlying herniated discs are poorly understood, necessitating research into these mechanisms and accessible diagnostic techniques. Our study employs high-resolution ultrasound and texture correlation to quantify strain patterns in intervertebral discs during dynamic loading.

A motion segment from the bovine caudal spine was prepared for investigating disc mechanics, secured in a mechanical tester, and subjected to axial compression. B-mode ultrasound images (40 MHz center frequency, Vevo3100) were acquired at two axial displacements: 0.5 mm and 1 mm. We used a direct deformation estimation (DDE) approach to analyze the image data and quantify strain within the disc, providing insights into its mechanics.

Our analysis revealed a heterogeneous strain pattern, with DDE highlighting interspersed areas of high tension and compression. Additionally, we observed that as displacement increases, first principal strain (E1) values rise, while second principal strain (E2) values decrease. Future work will encompass a broader sample size and a wider range of compression distances to further advance our understanding of NP and AF kinematics during loading. This research holds promise as ultrasound presents a novel, fast, and region-specific approach to quantify strain, offering exciting prospects for advancing our understanding of disc mechanics.