Ultrasound imaging of cervical spine motion for extreme acceleration environments

Abstract

Neck and back pain is one of the most common musculoskeletal complaints in personnel in variable acceleration environments such as astronauts and military pilots. Ultrasound is known for dynamic imaging and diagnostic workup of the axial and appendicular skeleton, but is not currently used to image the cervical spine, the injury of which may change the biomechanics of the cervical vertebrae, which CT and MRI (the current gold standard in cervical spine imaging) are poor at capturing. To validate ultrasound as a modality for imaging dynamic motion of the cervical spine several experiments were performed in static and dynamic human and animal (ovine) models: 1. Static analysis of ex-vivo ovine cervical spines imaged by ultrasound, MRI, and CT demonstrated that the imaging modality affected the measured intervertebral disc height (p<0.01); similar evaluation was done in-vivo in Emergency Department patients who received a CT scan as part of their clinical course that showed that ultrasound could fit into existing clinical workflows. 2. Dynamic analysis of isolated ex-vivo ovine cervical spinal segments intervertebral disc displacement with a mounted ultrasound probe demonstrated a measurement uncertainty of ± 0.2 mm and no bias at low frequency sinusoidal spinal displacement. A similar evaluation in-vivo with humans with an ultrasound probe mounted on a cervical-collar found a 0.8-1.3 mm amount of cervical spine distraction from the C4-5 Functional Spinal Unit. In human cadavers subjected to passive flexion and extension of the cervical spine, ultrasound measurements of the relative flexion/extension angles between consecutive cervical vertebrae were similar to fluoroscopy. 3. Ultrasound was able to record dynamic motion of the cervical spine in-vivo in running on a treadmill, during parabolic flight, and traveling over a rough road in a military vehicle. The ultrasound methods developed and tested in this thesis could provide an inexpensive, portable and safe technique that can identify and characterize cervical spine anatomy and pathology.