Abstract: BACKGROUND: Degeneration of the uncinate process and the development of osteophytes are recognized as prevalent factors contributing to cervical intervertebral foramen stenosis in individuals suffering from cervical spondylotic radiculopathy. Nonetheless, there is a notable scarcity of research data, both domestically and internationally, regarding C6 cervical spondylotic radiculopathy induced by mutations in the C6 uncinate process. Furthermore, the current body of imaging data is insufficient to establish a definitive diagnostic protocol for identifying the specific region affected by cervical spondylotic radiculopathy due to uncinate process degeneration.
OBJECTIVE: To delineate the spatial relationships between the uncinate process and adjacent anatomical structures using three-dimensional CT image reconstruction, to identify specific diagnostic regions within CT images for C6 nerve entrapment associated with uncinate process degeneration, and to guide key-hole surgical procedures aimed at decompressing the C6 nerve root canals.
METHODS: A cohort of 56 patients presenting with C5/6 unilateral cervical spondylotic radiculopathy, each patient fulfilled the predefined inclusion criteria, was enrolled in the study. This group comprised 29 males and 27 females, ranging in age from 35 to 71 years. Cervical spine CT data were imported into Mimics 21.0 software to construct a three-dimensional model of the cervical spine. The following parameters at the C5/6 level were measured: (1) Measurement on the sagittal plane of the uncinate process situated within the most constricted segment of the cervical intervertebral foramen: The vertical distance from the uncinate process situated within the most constricted segment of the cervical intervertebral foramen to the transverse section of the lower edge of the C5 pedicle and the upper edge of the C6 pedicle (a, b); (2) measurement on the cross section of the uncinate process situated within the most constricted segment of the cervical intervertebral foramen: The horizontal distance from the uncinate process situated within the most constricted segment of the cervical intervertebral foramen to the sagittal plane where the lowest point of the posterior edge of the upper endplate is located (c); (3) the horizontal distance from the uncinate process situated within the most constricted segment of the cervical intervertebral foramen to the sagittal plane of the medial and lateral margin of the pedicle of C6 (d, e); (4) the narrowest distance of intervertebral foramen (f); (5) measurement on the cross section of the lowest point of the posterior edge of the C6 upper endplate: the left and right distance from the upper endplate to the sagittal plane of the medial edge of the left and right pedicle of C6 (g, h); (6) on the median sagittal plane, the line connecting the anterior and inferior edge of the C5 inferior endplate (the line of inferior edge of the vertebral body ) was established, and the parallel line of the line of inferior edge of the vertebral body (the inferior endplate line) was established through the highest point of the C5 lower endplate. The parallel line (uncinate process line) of the line of inferior edge of the vertebral body was established through the uncinate process situated within the most constricted segment of the cervical intervertebral foramen, and the location between the line of inferior edge of the vertebral body, the inferior endplate line and the uncinate process line was observed on the median sagittal plane; (7) observation of the morphological characteristics of intervertebral foramen on the sagittal plane of the uncinate process situated within the most constricted segment of the cervical intervertebral foramen. All patients underwent single-port split endoscopic key-hole surgery on the cervical spine under the guidance of the above imaging data. The clinical efficacy was evaluated by visual analog scale and Japanese Orthopaedic Association scores before operation and 1 month, 6 months and the last follow-up after operation.
RESULTS AND CONCLUSION: (1) There was no significant difference in the related parameters between the two genders (P > 0.05). (2) There was no significant difference between the left side and the right side of a, b, c, d, e, f, g, and h (P > 0.05), and there was also no significant difference between g and h in the total sample (P > 0.05). (3) Visual analog scale score and Japanese Orthopaedic Association scores were improved at 1 month, 6 months, and the last follow-up after operation, and the difference was statistically significant (P < 0.05). (4) The region between the line of inferior edge of the vertebral body and the inferior endplate line was the absolute region and above the inferior endplate line was the region of above the inferior endplate line. The uncinate process region composed of the two regions was the specific region for the diagnosis of uncinate process degeneration by CT. (5) The intervertebral foramen region between the inner and outer edges of the sagittal pedicle included by the uncinate process region was a specific region in the diagnosis of cervical spondylotic radiculopathy. The uncinate process region with clinical symptoms and signs was accurate and reliable in the diagnosis of cervical spondylotic radiculopathy caused by uncinate process degeneration. (6) The uncinate process situated within the most constricted segment of the cervical intervertebral foramen was only the narrowest point of the intervertebral foramen, and the compression of the nerve root was often caused by the stenosis of the intervertebral foramen with the uncinate process at the uncinate process situated within the most constricted segment of the cervical intervertebral foramen as the center. (7) Different pathomorphological types of intervertebral foramen could be observed in the sagittal plane where the uncinate process situated within the most constricted segment of the cervical intervertebral foramen was located, and different types oppressed cervical nerve in different parts of intervertebral foramen. (8) Additional resection of uncinate process could be considered for grade 2 cervical intervertebral foramen stenosis; during the operation, the inferior margin of C5 pedicle and the upper, medial and lateral margin of C6 pedicle could be located and the uncinate process that was severely compressed cervical nerve can be removed. (9) Cervical spondylotic radiculopathy resulting from uncinate process degeneration warrants careful attention. The uncinate process region is particularly useful for CT diagnosis. Diagnosing cervical spondylotic radiculopathy caused by uncinate process degeneration using CT scans focused on this area, along with clinical signs and symptoms, is accurate and dependable, reducing the chance of missed or incorrect diagnoses. In cases of severe cervical nerve compression due to uncinate process degeneration, key-hole uncinate process resection may be considered.

Key words: cervical spondylotic radiculopathy, uncinate process, key-hole, imaging anatomy, three-dimensional reconstruction