Anatomical Evaluation of Spinal Nerve and Cervical Intervertebral Foramina in Anterior Controllable Antedisplacement and Fusion Surgery: A Cadaveric and Radiologic Study

OBJECTIVE: To achieve the anatomical evaluation of spinal nerve and cervical intervertebral foramina in anterior controllable antedisplacement and fusion (ACAF) surgery, a novel surgical technique with the wider decompression, through a cadaveric and radiologic study. METHODS: Radiographic data of consecutive 47 patients (21 by ACAF and 26 by anterior cervical corpectomy and fusion [ACCF]) who have accepted surgery for treatment of cervical ossification of the posterior longitudinal ligament(OPLL) and stenosis from March 2017 to March 2018 were retrospectively reviewed and compared between an ACAF group and ACCF group. Three postoperative radiographic parameters were evaluated: the decompression width and the satisfaction rate of decompression at the entrance zone of intervertebral foramina on computed tomography (CT), and the transverse diameter of spinal cord in the decompression levels on magnetic resonance imaging (MRI). In the anatomic study, three fresh cadaveric spines (death within 3 months) undergoing ACAF surgery were also studied. Four anatomic parameters were evaluated: the width of groove, the distance between the bilateral origins of ventral rootlets, the length of ventral rootlet from their origin to the intervertebral foramina, the descending angle of ventral rootlet. RESULTS: The groove created in ACAF surgery included the bilateral origins of ventral rootlets. The rootlets tended to be vertical from the rostral to the caudal direction as their takeoff points from the central thecal sac became higher and farther away from their corresponding intervertebral foramina gradually. No differences were identified between left and right in terms of the length of ventral rootlet from the origin to the intervertebral foramina and the descending angle of ventral rootlet. The decompression width was significantly greater in ACAF group (19.2 ± 1.2 vs 14.7 ± 1.2, 21.3 ± 2.2 vs 15.4 ± 0.9, 21.5 ± 2.1 vs 15.7 ± 1.0, 21.9 ± 1.6 vs 15.9 ± 0.8, from C(3) to C(6)). The satisfactory rate of decompression at the entrance zone of intervertebral foramina tended to be better in the left side in ACAF group (significant differences were identified in the left side at C(3/4), C(4/5), C(6/7) level, and in the right side at C(4/5) level when compared with ACCF). And decompression width was significantly greater than the transverse diameter of spinal cord in ACAF group. Comparatively, there existed no significant difference in the ACCF group besides the C(5) level. CONCLUSION: ACAF can decompress the entrance zone of intervertebral foramina effectively and its decompression width includes the origins and massive running part of bilateral ventral rootlets. Due to its wider decompression range, ACAF can be used as a revision strategy for the patients with failed ACCF.