The Influence of Cervical Traction, Compression, and Spurling Test on Cervical Intervertebral Foramen Size
The purpose of this study was to evaluate functional changes in the cervical intervertebral foramen during the axial compression test, axial distraction test, and Spurling test.
Although alterations of the cross-sectional area of the cervical intervertebral foramen during flexion/extension and rotation have been reported, there are no studies that have measured functional changes in foramen cross-sectional area or shape during the simulation of clinical tests for cervical radiculopathy.
Cervical radiculopathy is, by definition, a disease of the cervical nerve root and is most commonly caused by a cervical disc herniation or other space-occupying lesion, resulting in nerve root inflammation, impingement, or both. A number of tests have been reported as useful for the diagnosis of cervical radiculopathy and include the: foraminal compression test, Spurling test, distraction test, shoulder abduction test, and upper limb tension test. The purpose of these tests is to either induce or alleviate mechanical deformation on the cervical nerve roots by one the following mechanisms: enlargement or narrowing of the intervertebral foramen, and elongation of the neural elements creating increases in intrathecal pressure.
The foraminal compression test is designed to provoke symptoms and is used if the patient complains of pain potentially arising from compromise of a nerve root. It is advocated performing the foraminal compression test in 3 stages, each of which is increasingly provocative. If at any stage symptoms are increased then the test is positive. The first stage involves axial compression applied through the head, with the neck in neutral. The second stage involves axial compression with the neck in extension, and the final stage is axial compression with the neck in extension and rotation, first to the unaffected side, then to the symptomatic side. The third part of the test more closely follows Spurling test. In contrast, the distraction test is used to alleviate symptoms and is performed in the presence of radicular symptoms. With the patient in supine, the examiner places one hand under the patient’s chin and the other hand around the occiput, then slowly distracts the patient’s neck. An axial traction force of approximately 10 to 15 kg is applied. The test is classified as positive if the pain is relieved or decreased when the head is distracted, indicating pressure on nerve roots that has been relieved. To date no studies have investigated the validity of the foraminal compression test or the distraction test.
The cervical nerve roots and ganglions pass through the foramen at or below the level of uncovertebral and zygapophysial joint lines with the large sensory roots above and behind the small motor roots. The cervical intervertebral foramens are almost filled by the cervical dorsal root ganglions. For these anatomic reasons, it seems reasonable to suggest that cervical radiculopathy is strongly correlated with both the crosssectional area and shape of the intervertebral foramen.
Previously, it has been difficult to evaluate the shape of the foramen by quantitative methods. In this present study, the ratio of the anteroposterior
dimensions, compared with control condition (RAPC) was employed to measure the change in shape of the foramen during various tests used in the assessment of cervical radiculopathy. The authors found a significant difference in RAPC between the axial compression test and Spurling test only at the C4–C5 and C5–C6 foramen. Thus, it can be inferred that the combination of cervical extension, rotation, and lateral flexion alters the anteroposterior space of the intervertebral foramen only at C4–C5 and C5–C6. This result might be explained by the relatively greater segmental mobility and flexibility at C4–C5 and C5–C6 when compared to all other levels apart from C1–C2. It is possible that the range of movement employed in this study during Spurling test was not sufficient to reach as far as the lower cervical vertebrae.
Furthermore, a previous study has shown that segmental coupled lateral flexion during axial rotation, is much less in the lower than middle cervical spine. The protocol of Spurling test is obscure. These results indicate that further studies are required to more clearly define the important parameters of this commonly used clinical test to determine what range of motion is required to maximally impact on all cervical levels.
At the level of C7–Th1 foramen cross-sectional area did not increase during the distraction test. Increased foramen cross-sectional area seen at the C4–C5 to C6–C7 levels might be explained by a reduction in cervical lordosis during the distraction test, rather than vertebral separation. Reduction in the cervical lordosis will increase segmental flexion which is likely to increase foramen cross-sectional area. Support for this hypothesis is gained by our observation of change in the cervical lordosis on the monitor during MRI testing of the distraction test. Thus mechanical assessment using a combination of the distraction test and Spurling test seem to be more appropriate to evaluate middle cervical problems rather than lower problems.
In this study, the mean foramen cross-sectional area at the level of C4/C5– C7/Th1 in the control condition closely corresponded with previous reports. Additionally, during the distraction test the increasing ratio of the foraminal size at C5–C6 was almost the same as a previous study using CT for the measurement. Certainly, it has been shown that the foramen cross-sectional area measured by MRis not the true area of the foramen. Compared with CT, MR consistently underestimates the diameter of the foramen cross-sectional area because of magnetic susceptibility,truncation, and pulsation artifacts of cerebrospinal fluid. According to Tsuruda and Remley the size of the foramen cross-sectional area can vary when compared with CT between 8% and 27% when measured using a 3-dimensional-GE sequence with echotime (TE) of between 11 and 22 ms. Based on cadaveric measurement, the true size of the foramen at C4/C5–C7/Th1 has been shown to be between 35 and 20 mm2. However, this current study used a ratio to assess change in shape of the foramen. It can be argued that a ratio is less likely to be affected by artifacts generated during the MRI and is therefore appropriate to assess functional changes in the foramen during simulated clinical tests.
It has been said that clinically, for the middle and lower cervical spine, a distraction force of between 11 and 20 kg is effective in reducing symptoms in conditions where a separation of the intervertebral space is desirable. Additionally, it has been reported that more than 15 kg distraction force is excessive as it has the potential to cause neck pain. Therefore, in this study a 12 kg force was chosen from the view points of safety and effectiveness.
During 3 clinical tests for cervical radiculopathy functional, relevant, and changes in the cervical intervertebral foramen were evident particularly in the middle cervical spine.