Cervical nerve root displacement and strain during upper limb nueral tension testing
Clinical examination of neural pathology involving cervical nerve roots is difficult due to the transient nature of pathologies such as cervical radiculopathy, entrapment neuropathies, and thoracic outlet syndrome. Significant displacement and strain occur in lumbosacral nerve roots during neurodynamic testing of the lower limb; however, a complete examination into the biomechanics of cervical nerve roots during neurodynamic testing has not been performed. Biomechanical studies have found that the foraminal ligaments in the lumbar spine limit displacement and strain of the lumbosacral nerve roots, but similar studies have not been conducted in the cervical region. Therefore, the purposes of this dissertation were to determine the displacement and strain of cervical nerve roots C5-C8 during upper limb neural tension testing (ULNTT) and to determine the role of the foraminal ligaments in the cervical spine. Eleven unembalmed cadavers were positioned as though undergoing ULNTT. Radiolucent markers were implanted into cervical nerve roots C5-C8. Postero-anterior fluoroscopic images were captured at resting and ULNTT positions. Foraminal ligaments were then selectively cut and ULNTT and imaging procedures were repeated. Images were digitized and the markers were analyzed for positional changes between positions by t-tests and ANOVAs. Significant inferolateral displacement (average, 2.16-4.32 mm, P < 0.001) and strain (average, 6.80-11.87%, P < 0.001) of cervical nerve roots C5-C8 were detected during ULNTT. Additionally, there was a significant difference in inferolateral displacement and strain between the C5 and C6 nerve roots (3.15 vs. 4.32 mm, P = 0.009; 6.60 vs. 11.87%, P = 0.03). Selective cutting of the foraminal ligaments resulted in significant increases in inferolateral displacement (average, 2.94 to 3.87 mm, P < 0.05) and strain (average, 9.33 to 16.31%, P < 0.03) of cervical nerve roots C5-C8 during ULNTT. The results provide a mechanical foundation for provocative neurodynamic testing of the cervical region. Upper limb neural tension testing causes significant inferolateral displacement and strain in nerve roots C5-C8 and may be useful in clinical evaluation of neural pathology in the cervical region. The foraminal ligaments in the cervical spine limit cervical nerve root displacement and strain during ULNTT. The foraminal ligaments appear to play a protective role, dissipating strain to cervical nerve roots during tension events.