Study of impact loading on the cervical spine using digital image correlation

Digital Image Correlation (DIC) has become a staple of structural engineering. DIC is also particularly appealing in biomechanical studies as, contrary to other more traditional techniques, it allows visualisation of specimen strains and deformation over a large area. DIC has been successfully used by our group to study Cervical Spine Injuries (CSIs). The aim of this study was to assess strain and deformation patterns of cervical specimens under impact loading conditions using DIC. Six porcine cervical spines (containing C2 to C6 vertebrae bodies) were dissected, potted in PMMA bone cement, mounted in an impact cage and tested using a custom vertical impact rig. Impacts were applied via falling mass of 12.86 kg constrained within a linear bearing assembly. A drop height of 250 mm was used producing an impact velocity of 2.2 m/s. Image data was captured with two high-speed cameras and viewer software (Photron Europe Ltd, UK) and digital image correlation of the video data was performed (Vic-3D, Correlated Solutions, USA). The results showed that five out of six specimens demonstrated buckling behaviour, with two specimens presenting visible vertebral fracture injuries in C4 and C5. Higher strains were seen around C4/C5 in most of the specimens, with a mean of 2.4 +/- 1.3 % and peaks of 4 %. The pattern of observed deformation, i.e. buckling, is consistent with literature data attributing injury of the cervical spine to this deformation mode. This study illustrated the capability of DIC of analysing fractures in CSIs and re-enforced the theory of injury by buckling.