Development of Ultrasound to Measure In-vivo Dynamic Cervical Spine Intervertebral Disc Mechanics

Abstract

Abstract : Neck pain is pervasive problems in military population, especially in those working in vibrating environments. Previous studies show neck pain is strongly associated with degeneration of Intervertebral Disc (IVD), which is commonly caused by repetitive loading and aging. To reduce the risk of cervical spine disease, there is a need to measure the effect by helmet, equipment and seating. However, in-vivo displacement and loading condition of cervical spine are difficult to measure during operation. Clinical ultrasound (US) is being explored as a valuable tool to image motion of the cervical spine, specifically vertebral motion and intervertebral disc deformation. A dual US imaging system is being developed to measure 3D motion of contiguous cervical vertebrae and IVD strain ( height of IVD/original IVD height) of intervening functional spine units (FSU). This system was validated ex-vivo using cadaveric C-spines mounted in a servo-hydraulic material testing machine by comparing dynamic US measurement to direct measurements using a linear variable differential transformer (LVDT) system in our previous 2013-2014 annual progress report. In year 2014-2015, we further developed the performance of hardware/software of dual ultrasound system. The capability of dual US to measure C-spine properties in-vivo in simulation environment is currently being tested. Biomechanics finite element(FE) models were developed to examine how dynamic forces applied to the occipital-atlantal junction (i.e. C1) are transferred to the subaxial C-spine.