Assessing the Ability of Pressure Sensors Inserted into Intervertebral Discs to Detect Compression, Flexion, and Combined Flexion + Compression Loading

<div>Ongoing research in simulated vehicle crash environments utilizes postmortem human subjects (PMHS) as the closest approximation to live human response. Lumbar spine injuries are common in vehicle crashes, necessitating accurate assessment methods of lumbar loads. This study evaluates the effectiveness of lumbar intervertebral disc (IVD) pressure sensors in detecting various loading conditions on component PMHS lumbar spines, aiming to develop a reliable insertion method and assess sensor performance under different loading scenarios. The pressure sensor insertion method development involved selecting a suitable sensor, using a customized needle-insertion technique, and precisely placing sensors into the center of lumbar IVDs. Computed tomography (CT) scans were utilized to determine insertion depth and location, ensuring minimal tissue disruption during sensor insertion. Tests were conducted on PMHS lumbar spines using a robotic test system for controlled loading in flexion, compression, and a combination, while monitoring pressure changes. The compression force, flexion angle, and sensor-recorded IVD fluid pressure were recorded during tests. CT images were analyzed to assess sensor placement and its impact on sensing ability. Pressure readings during various loading conditions were examined for different specimens, with data reported from the beginning of tests through relevant loading phases. The study successfully established a methodology for inserting pressure sensors into the IVD and assessed their ability to detect changes in flexion angle, compression, and combined loading. Sensors accurately tracked compression force and detected changes in flexion angle, although with some differences in response. Sensors placed optimally showed expected responses, while those placed suboptimally exhibited variability, particularly in detecting changes during flexion. This variability underscores the importance of sensor placement for accurate detection of loading states. Overall, the study provides a foundation for utilizing pressure sensors to monitor loading states in sled tests, with future work focusing on refining differentiation between loading types.</div>