The lateral blocks of the cervical spine are located at the posterior lateral aspect of the vertebral body, at the union of the vertebral roots and the vertebral arches, and consist of superior articular processes that protrude cephalad and inferior articular processes that protrude caudad, respectively, one on each side. The upper and lower articular processes of adjacent segments form small joints and join the lateral blocks together to form a bony column. Together with the anterior vertebral body and intervertebral discs, the bilateral small joints and lateral blocks form the intervertebral joints of the cervical spine and form three bony columns parallel to each other, which form the basic framework of cervical spine stability. Detailed anatomical measurements of the lateral blocks have not been reported. Howards observed that the distance between the centers of adjacent lateral blocks averaged 13 mm and that screws entered the lateral blocks at 15° cephalad and 30° lateral to a depth of 10-11 mm without touching the nerve roots, which to some extent reflects the height and anterior-posterior diameter length of the lateral blocks. The posterior spinal nerve branch is another important structure surrounding the lateral mass, and Ebraheim found that the average height of the posterior spinal nerve branch tapers from C3 (2.2 ± 0.6) mm to C7 (1.2 ± 0.2) mm, and the average distance from the posterior spinal nerve branch to the tip of the superior articular eminence is at C5 (2.2 ± 0.6) mm. The average distance from the posterior branch of the spinal nerve to the tip of the superior articular eminence was greatest at C5 (7.4±1.6) mm and least at C7 (5.5±2.9) mm, and the angle between the posterior branch of the spinal nerve and the superior articular surface of the lateral mass ranged from 23.3°±14.3° to 29.8°±11.2°. The integrity of the small joints of the cervical spine plays a significant role in maintaining the stability of the cervical spine. zdeblick et al. made observations on the extension, flexion and rotation movements of human cervical spine specimens under axial loading and found that the torsional resistance of the small joints was significantly reduced after 50% of them were removed. In extension and flexion movements, there was no significant difference in stress deformation about the neck between intact specimens, laminectomized specimens and specimens with 25% subtotal joint resection, whereas strain increased by 2.5% in specimens with 50% subtotal joint resection and by 25% in specimens with 75% and 100% resection.Robert’s study confirmed that laminectomy destabilizes the cervical spine, while lateral-posterior subtotal joint fusion can regain stability and prevent progressive deformity in the laminectomized cervical spine. This is accomplished by drilling a hole through the tuberosity and tying a longitudinal strip of bone to the tuberosity with a wire. In a shear test of a cervical motion segment including two vertebrae and surrounding structures, Richard et al. found that the ability to resist shear was significantly weakened when more than 50% of the subtalar joint was removed (subtalar fractures occurred during the experiment). . Biomechanical tests by Joseph et al. showed that unilateral subtotal joint resection resulted in an average reduction of 31.6% ± 9.7% in its ability to carry flexion loads, while bilateral subtotal joint injury resulted in an average reduction of 53.1% ± 11%. Liming et al. further confirmed the effect of small joint injuries on the overall stability of the cervical spine. They found that the magnitude of rotational motion increased with the extent of subtotal joint resection, with the greatest change occurring in specimens with 50% and 75% bilateral subtotal joint resection and a concomitant increase in the stress on the annulus fibrosus; in lateral flexion, the increase in rotation was 11% and the stress on the annulus fibrosus was 30%. They concluded that the increase in annulus fibrosus stress caused by subtotal joint resection was greater than that caused by intervertebral joint straightening, and that bilateral subtotal joint resection of 50% or more significantly increased the stress on the annulus fibrosus and the range of motion of the motion segment. This shows that the small joints of the cervical spine play an important role in maintaining the stability of the cervical spine. The lateral blocks and joints on both sides play a pillar role for the posterior stability of the cervical spine, and the destruction of the small joints means the destruction of the overall stability of the cervical spine; on the contrary, the stability of the small joints constructs the overall stability of the cervical spine. 1. Application of cervical lateral blocks in posterior internal fixation Although studies on the anatomical measurement of lateral blocks have not been reported, posterior cervical internal fixation methods related to lateral blocks have long been used in clinical practice. The earliest use of plate screws for posterior cervical internal fixation via the lateral block was by Roy-Camille, and this technique was later improved by Magerl and Seemann with the aim of increasing the occlusion of the screws with the lateral block, the main difference being the different trajectory of the screws in the lateral block. Heller et al. compared Roy-Camille’s and Magerl’s techniques anatomically and screwed screws into C3-C7 lateral blocks on 26 fresh cervical specimens according to the methods described by Roy-Camille or Magerl to determine the potential risk to nerve roots, vertebral arteries, and small joints posed by both methods. The potential risk to the nerve roots, vertebral arteries and small joints was determined by both methods. In the Roy-Camille technique, the nail entry point is at the center of the lateral block (posterior apex of the tuberosity), the screw is oriented: from posterior medial to anterior lateral, at an angle of 10° to the sagittal plane to avoid the vertebral artery, and the screw is 3.5 mm in diameter and penetrates the anterior and posterior bilayers of the bone cortex. In the Magerl technique, the screw entry point is 2-3 mm above the midpoint of the lateral block, tilted upward parallel to the articular surface of the superior articular eminence, and tilted outward at 25°, with the screw penetrating the anterior and posterior cortices and the tip located on the superior lateral aspect of the anterior articular eminence. In both methods, the location of the tip of the nail is determined by the three-zone grading sys-tem of the lateral block, i.e., the lateral block is divided into three zones: upper zone from the superior edge of the superior articular eminence to the root of the superior transverse eminence; middle zone between the upper and lower edges of the transverse eminence; and lower zone from the lower edge of the transverse eminence to the lower edge of the inferior articular eminence. The upper 1/3 (upper zone) of the lateral block represents the position where the tip of the Magerl technique screw is located, and the lower 1/3 (lower zone) is the correct position where the tip of the Roy-Camille technique nail is located. In the experiment, the position of each screw was evaluated according to its potential risk to the nerve root, vertebral artery, its effect on the small joint, and the zone in which it was located. The results showed that the Roy-Camille technique had a low probability of damaging the nerve root and a low probability of the screw entering beyond zone three, while the Magerl technique had a low risk of damaging the small joints and neither technique posed a threat to the vertebral artery or spinal cord. The experiment also showed that the chance of nerve root injury was related to the surgeon’s technical proficiency, and that the chance of nerve root injury was significantly reduced once the technique was skilled. Howards et al. also studied the distance between the C3-C7 tuberosity and the morphology of the C7-T2 pedicle in order to determine the potential risk of posterior cervical transforaminal plate screw fixation. To this end they studied 22 cervical specimens and found that the distance between the centers of adjacent blocks from C3-C7 up and down varied considerably from individual to individual, ranging from 9-16 mm with an average of 13 mm, and that the design of the plates had to accommodate this variation in different individuals and between segments. Since the nerve root penetrates anterolaterally in the superior articular process, the greater the angle medially and cephalad, the greater the likelihood of injury to the nerve root, and the ideal penetration point for the screw is at the union of the superior edge of the transverse process and the lateral block. Anderdon et al. performed posterior cervical A0 reconstruction plate internal fixation and bone grafting in 30 patients with cervical instability, using the same nail entry point and Howards method, with the nail entry direction: 10° outward, 30° upward -Ebraheim et al. concluded that Magerl and Anderson’s approach was more likely than Roy-Camille’s technique to injure the posterior branch of the spinal nerve and cause unilateral cervical dorsal pain or sensory abnormalities, based on their determination of the location of the posterior branch of the spinal nerve. The anatomical study by Ebra-heim et al. confirmed that a 10° outward approach to the nail does not pose a threat to the vertebral artery. While most of the above-mentioned studies address the surgical risks, John et al. focused on the magnitude of the binding force of different types of screws to the lateral block. The study used 12 fresh cervical specimens, which were radiologically determined to be intact, followed by CT scans to determine the bone density of the cancellous bone of the C 2-C7 vertebral body in each specimen; six different screw diameters and threads were tested (2.7, 3.2, 3.5, and 4.5 mm cortical screws, 3.5 mm cancellous screws, and 3.5 mm self-tapping screws), were accurately fixed to the lateral cervical block, and then the axial pull-out resistance of the screws was measured. The data were analyzed to determine the correlation between screw diameter, thread shape, cervical segment, bone density, and penetration of the double-layered bone cortex. The results showed that the maximum pull-out resistance was for 3.2, 3.5, and 4.5 mm diameter cortical screws, all of which had to pass through the bilaminar cortex, and the minimum pull-out resistance was for 3.5 mm self-tapping screws (either through the single or bilaminar cortex). The cancellous bone density of the vertebral body was not associated with pull-out resistance, and there was no significant difference in bone density between cervical segments, yet there was a significant difference in screw pull-out resistance between segments, with the greatest pull-out resistance at C4 and decreasing cephalad and caudad. The study data suggest that the surgeon should consider not only the type and size of the screw, but also whether the screw should be drilled through a single or double layer of bone cortex, as penetrating a double layer of bone cortex poses a greater risk to the local anatomy, but because the lateral blocks of the cervical spine on the cephalocaudal side have a weaker bite with the screw, it is desirable to drill through a double layer of bone cortex in these areas. A biomechanical trial of a cervical stabilization device using human cervical specimens and Roy-Camille plates found that Roy-Camille plates were effective in fixing severely unstable or severely injured cervical vertebrae; screw dislodgement was most likely to occur at the cephalocaudal end of the cervical spine, i.e., the screws at the ends of the plates were the weak link in fixation. Statistical analysis of the medical records supports these results. 17 patients with multisegmental cervical spondylosis were fixed internally by posterior trans-lateral block, and l case showed loosening of the C7 lateral block screws (asymptomatic). Another important anatomical structure adjacent to the lateral block of the cervical spine is the pedicle. The widespread use of the pedicle internal fixation technique in the thoracolumbar spine has prompted a similar fixation of the cervical spine with the entry point of the screw on the lateral block. In this regard, Sun Yu et al. in China observed the cervical arch in 50 healthy adults and showed that the conditions for internal fixation with pedicle screws were available for C3-C7, which provided an anatomical basis for screw design and surgical positioning. Biomechanical tests were performed for both transforaminal and lateral internal fixation. The results confirmed that the pull-out resistance of the pedicle screws was significantly greater than that of the lateral block screws. Further anatomical studies of the lower cervical arch fixation were performed to precisely locate the nail entry point, and no neurological, vascular, or internal fixation complications were observed in any of the 19 clinical applications. However, as far as the load on the cervical spine is concerned, further research is needed to determine whether the lateral block internal fixation can achieve the fixation requirements without the need for the more complicated transpedicular internal fixation technique. Comparison of several cervical internal fixation techniques Posterior cervical internal fixation techniques have become an effective treatment for cervical injuries and instability, and Gill et al. compared four different posterior internal fixation methods in an attempt to reveal the relative stability provided by different surgical methods through biomechanical experiments. These included (1) Rogers interspinous wire internal fixation, (2) Halifax plate hook, (3) trans-lateral block 1/3 tubular plate internal fixation (with single-layer cortical screws), and (4) trans-lateral block 1/3 tubular plate with double-layer cortical screws internal fixation. Using flexion and extension motion tests on human cervical specimens, it was found that the fourth procedure described above provided the strongest stability, while the stability achieved by the other three methods was relatively weak.Weis et al. also showed that posterior trans-lateral block internal fixation provided significantly greater stability to the cervical motion segment and the total cervical spine than posterior wire internal fixation.Roy-Camille’s study of Gill et al. found that all posterior internal fixation techniques were superior to Garspar anterior cervical plates in cases of flexion-type ligament injuries. et al. compared sublaminar wire fixation, Rogers wire fixation, Bothlman triple wire fixation, AO hook plate fixation, and Cas-par anterior plate fixation in in vitro animal models and human cervical specimens. There were no significant differences between any of these two methods in terms of flexion resistance and rotational stability, however, Caspar anterior plate significantly increased posterior cervical stress compared to all posterior internal fixation methods. Thus, it is less effective in the treatment of flexion injuries. In terms of trans-lateral plate internal fixation itself, there are differences in the stabilizing effect provided by different nail approach directions or different travel distances of the screws in the lateral block.Montesano and Jnach compared the Roy-Camille and Magerl approaches and found that the Magerl technique had a more plausible stabilizing effect. Among the posterior internal fixation techniques, the most stable is the Magerl hook plate technique, especially in terms of resistance to flexion stresses. The upper part of the plate is screwed to the lateral block and the lower part is hooked to the lamina of the inferior vertebrae. In extension injuries, the posterior wire internal fixation technique is less stabilizing, in which case the posterior plate, however, provides a more credible stabilizing effect. Although Rogers Mcfee, Edwards et al. reported the credible efficacy of posterior cervical wire internal fixation techniques for different types of cervical spine injuries, the use of wire internal fixation techniques is also limited in patients with multisegmental laminectomy and lamina and spinous process fractures.Joseph demonstrated that in segmental pushover cervical spine, transarticular eminence and cervical spinous process penetration below the laminectomy segment Wire binding of the longitudinal bone block does not maintain cervical stability. 3. Conclusion The bilateral lateral block joints and the anterior vertebral body and intervertebral disc structures together constitute the basic framework of cervical spine stability. Disruption of the above structures means disruption of the stability of the cervical spine. The posterior cervical internal fixation technique is being more and more widely used, and the procedure can be summarized into two categories: one is wire-bound internal fixation, and the other is trans-lateral block plate and screw internal fixation, of which the latter has a wider use. The incidence of injury to nerve roots, vertebral arteries, and small joints is related to the operator’s proficiency. The feasibility of transperineal internal fixation has been experimentally demonstrated and has been used clinically for the first time. Since satisfactory fixation has been achieved with trans-lateral block internal fixation, the need for transpedicular internal fixation has yet to be demonstrated. In addition, the surgical risks of the two have not been compared. A 5-year search of Chinese and foreign language data did not reveal any reports of detailed anatomical measurements of the lateral block. However, Johng Heller’s experiment used 3.5 mm diameter screws, and Howards’ study found that the distance between the centers of adjacent lateral blocks averaged 13 mm and the depth of screw entry averaged 10-11 mm. This outlines the size of the lateral blocks to some extent. Biomechanical tests showed that cortical bone screws with diameters of 3.2, 3.5, and 4.5 mm, which penetrated the double-layered bone cortex, had the greatest pull-out resistance, with the 3.5 screws having the greatest strength. With internal fixation via lateral plate screws, the screws at the head and tail of the plate are the weak points of fixation.