Dynamic failure localization in spinal specimens using acoustic emissions
Understanding the dynamic failure behavior of the spine is important in prevention of acute spinal injuries and chronic spinal pain. Traditional failure identification techniques are poor indicators of less severe injuries including incipient failure. One promising technique for sensitively assessing spinal injury is dynamic mapping of acoustic emissions. This technique allows detection of small failures in the spine, which are important for understanding spinal injuries at occupational exposure levels and for understanding the progression of catastrophic spinal injuries. A whole cervical spine was excised and instrumented with a position sensor, two 6-axis load cells, and an array of acoustic sensors. Tap tests were performed to determine the feasibility of using localization algorithms in the spine. The specimen was loaded in compression with increasing displacements until the first acoustic emission was measured. Acoustic emissions were localized with a mean error of 3.63mm and 10.7mm in the tap tests. The failure was localized to the right lateral side of C4 which was 12.2mm from a failure in the osteophyte seen in micro-CT and an associated failure in the anterior longitudinal ligament. These failures occurred during the loading and would not have been detected using traditional force time history analysis. This technique provides improved understanding of failure in spinal biomechanics, especially for low-level incipient and repeated loading injuries potentially associated with pain.
