Exploring upper cervical flexion to stress the transverse ligament of the atlas

Accurate assessment of traumatic upper cervical spine injuries in the physiotherapy clinical setting is challenging. Imaging and manual stress tests are utilized to evaluate the integrity of the craniovertebral (CV) ligaments. However, current approaches have limitations. These include a lack of standardized imaging protocols to identify CV ligament injuries, and the manual stress tests lack sensitivity and are difficult to perform. The objectives of this thesis were: 1) to understand the anatomical complexity and role of the TLA; 2) to understand how disruption of the TLA is assessed; 3) to explore a novel approach to ligamentous stress testing and imaging of the TLA in healthy subjects using magnetic resonance imaging (MRI). The anatomy, imaging and clinical testing of the TLA are explored in a narrative literature review. This informed a concept that upper cervical flexion could offer a novel approach to stress testing the TLA. This concept was first explored in a cadaveric dissection (n=1) which visually confirmed that the TLA was put under tension during upper cervical flexion. This was followed by a proof-of-concept (POC) MRI study of healthy participants (n=5) exploring length changes in the TLA in three positions (neutral, upper cervical flexion, Anterior Shear Test). Potential changes in TLA length were measured by two raters using the anterior atlanto-dental interval (ADI) in the sagittal and axial planes, and the bilateral atlanto-axial interval (AAI) in the coronal plane for each de-identified participant. The TLA was also directly visualized in the three positions. As a POC design, measurements from the MRI study resulted in substantial uncertainty. There was a general trend of the sagittal ADI increasing from neutral to flexion for both raters, but it was not statistically significant. The left AAI neutral to flexion measurement for Rater 2, who had a higher intra-rater reliability than Rater 1, was close to being statistically significant. The AAI measurement provided a higher ICC(2,1) for each rater than the ADI, indicating it may be a more consistent measurement. There were many factors (e.g. long sequences creating tissue creep, inexperience of raters with choosing and measuring CVJ MRI images) that may have limited the findings and comparability of this study with other literature. Although the MRI portion of this study was inconclusive, in combination with the results from the literature review and anatomical study there is evidence to indicate that the concept of flexion as a stress position for the TLA during imaging is worth exploring further. The MRIiii study also makes clear that there are significant technological measurement challenges to overcome in this field.