Anatomical Importance Between Neural Structure and Bony Landmark in Neuroventral Decompression for Posterior Endoscopic Cervical Discectomy

Abstract

Objective: This study aims to investigate the anatomical relationship among the nerve roots, intervertebral space, pedicles, and intradural rootlets of the cervical spine for improving operative outcomes and exploring neuroventral decompression approach in posterior endoscopic cervical discectomy (PECD).

Methods: Cervical computed tomography myelography imaging data from January 2021 to May 2023 were collected, and the RadiAnt DICOM Viewer Software was employed to conduct multiplane reconstruction. The following parameters were recorded: width of nerve root (WN), nerve root-superior pedicle distance (NSPD), nerve root-inferior pedicle distance (NIPD), and the relationship between the intervertebral space and the nerve root (shoulder, anterior, and axillary). Additionally, the descending angles between the spinal cord and the ventral (VRA) and dorsal (DRA) rootlets were measured.

Results: The WN showed a gradual increase from C4 to C7, with measurements notably larger in men compared to women. The NSPD decreased gradually from the C2-3 to the C5-6 levels. However, the NIPD showed an opposite level-related change, notably larger than the NSPD at the C4-5, C5-6, and C7-T1 levels. Furthermore, significant differences in NIPD were observed between different age groups and genders. The incidence of the anterior type exhibited a gradual decrease from the C2-3 to the C5-6 levels. Conversely, the axillary type exhibited an opposite level-related change. Additionally, the VRA and DRA decreased as the level descended, with measurements significantly larger in females.

Conclusion: A prediction of the positional relationship between the intervertebral space and the nerve root is essential for the direct neuroventral decompression in PECD to avoid damaging the neural structures. The axillary route of the nerve root offers a safer and more effective pathway for performing direct neuroventral decompression compared to the shoulder approach.

Keywords: Cervical spine anatomy; Endoscopic spine surgery; Myelography; Posterior cervical discectomy.

Fig. 1.

Schematic diagram illustrating the establishment of the standardized observation plane at the C6–7 segment. Images from left to right represent respectively sagittal, coronal and transverse plane computed tomography images. The red, yellow and blue lines represent the coronal, transverse and sagittal axes, respectively. (A–C) Orient the pedicles on both sides of the lower vertebral body, and ensure that the coronal axis is parallel to the posterior wall on median sagittal plane. (D–F) Relocate the intersection of axes to the center of one side’s pedicle on the transverse plane. (G–I) Shift the intersection of axes to the highest point of the inferior edge of the nerve root on the coronal plane. (J–L) Align the coronal axis with the posterior wall of the lower vertebral body on sagittal plane.

Fig. 2.

Schematic diagram depicting measurements of all parameters at C6–7 level. (A1–3 and B1–3) UVRA/UDRA: the uppermost ventral/dorsal rootlets angle; MVRA/MDRA: the middle ventral/dorsal rootlets angle; LVRA/LDRA: the lowest ventral/dorsal rootlets angle. (C1–3) Point A: the highest point of the inferior edge of the nerve root; point B: the highest point of the superior edge of the nerve root; WN (AB): width of nerve root; NSPD: the nerve root-superior pedicle distance; NIPD: the nerve root-inferior pedicle distance. (D1–3) Point A: the projection point of the highest point of the inferior margin of the nerve root; points B and C: the intersection of the sagittal axis with the upper and lower margins of the intervertebral space.

Fig. 3.

The anatomic relation between the intervertebral space and the nerve root. (A1–3) The multiplane reconstruction images of the axillary type at the C6–7 level. (B1–3) The multiplane reconstruction images of the anterior type at the C4–5 level. (C1–3) The multiplane reconstruction images of the shoulder type at C2–3 level.