The motion of an intact cervical spinal segment is managed by the coordination of paravertebral muscles, discs, facet joints, and ligaments. Any injury to these structures can influence the function of the cervical spine, particularly in cases with PLC injury . In previous spinal kinematic studies, researchers analyzed changes in the ROM and locations of the instantaneous axes of rotation of spinal segments to evaluate the biomechanical role of each ligament by sequentially cutting the ligaments [24–27]. The results of these studies indicate that SSL or ISL ligaments are the most resistant structures of the PLC to compression forces, and FJC contributes less to resistance to compression forces. Therefore, when the PLC elements are injured, a major proportion of this force shifts onto the intervertebral disc because of the loss of resistance to compression forces. Meanwhile, the cervical spine loses the restriction of the posterior ligament, leading to vertebral instability, spinal canal compression, and cervical spine sequence disorder.
A posterior element failure commonly occurs alongside an anterior structure injury . Therefore, such a simple posterior tension band injury without fracture is rare. The commonly used operative treatment for cervical PLC injury includes pedicle screw and plate fixation through anterior approach, and screw-rod constructs using transfacet screws or lateral mass screws through posterior approach. To achieve the cervical spine fusion, they can also be combined to stabilize three-column damage or highly unstable cervical spine [28–35]. A posterior compression type construct and fusion is favorable for treating thoracolumbar spine PLC injury (often with fractures) due to its strong fixing ability, which is enough to withstand the gravity of the upper body . However, the cervical spine has high requirements for movement and flexibility, which are inevitably limited by fusion. Besides, an increased risk of adjacent segment degeneration cannot be ignored either . Conversely, the fusion treatment is less favorable for cervical PLC injuries.
Non-fusion therapy with artificial ligament reconstruction for PLC injuries on humans has not been reported. However, previous researchers have proposed some approaches similar to the one introduced in the present study. Ngo et al. used interlaminar wiring fixation looped between the spinous process base to treat patients with fracture and contralateral dislocation of the twin facet joints of the lower cervical spine . This is similar to our reconstruction of the interspinous ligament using the artificial ligament with a figure “8” cross-tie. However, this method is essentially a fusion therapy due to the high rigidity of the wire. Moreover, the technique has certain risks; it may cause serious neurologic sequelae because the wire is passed beneath the lamina. Wang et al. conducted biomechanical test of bilateral facet joint stabilization using a bioderived tendon with a figure “8” cross-tie through the bone tunnels drilled through the facet joint to simulate the function of broken joint capsule ligaments. This inspired the creation of our new technology . Besides, Hamoud et al. presented a new method for stabilization of a rare unstable flexion-distraction injury of the upper cervical spine in a toddler. They performed a posterior approach fixation of the spinous processes with absorbable sutures without fusion. The toddler had a good prognosis and no complications . Though the unique anatomy and biomechanics of the pediatric cervical spine determine the difference between pediatric and adult injury patterns and treatment options, it still illustrates the feasibility of non-fusion technologies.
Based on previous clinical research and patient condition, we created a novel surgical technique, involving artificial ligament anchoring of the facet joints and artificial ligament reconstruction between spinous processes, to simulate the function of damaged FJC, SSL, and ISL. However, currently, this technology is only applicable to a pure rear tension band damage case (AO type B2 according to the AOS pine subaxial cervical spine injury classification system ). It might be more suitable for traditional fusion if combined with a fracture or severe cervical instability.
The advantages of this technique are as follows: (1) The target structure of the surgical procedure is direct and the operation procedure is clear, which improves repeatability. (2) It uses ligament-screw anchoring construct and interspinous artificial ligament reconstruction to separately simulate the FJC and the interspinous spine ligament (SSL and ISL) functions. This restores the anatomical structure and biomechanical function of the cervical spine. (3) Three parallel artificial ligaments provide sufficient tension for the cervical spine and guarantee the maintenance of stability and normal physiological curvature of the cervical spine. In addition, the figure “8” fixation method between the spinous processes also achieves a balance of forces on both sides of the spinous process. (4) The ligament is an elastic material that can be properly extended or contracted according to the patient’s neck movement, which greatly preserves the patient’s neck mobility. (5) Finally, we improved the stabilization method of bilateral facet joints in Wang et al study . The bone tunnels drilled through the facet joint for the passage of bioderived tendon may cause facet joint degeneration; hence, we used lateral mass screw anchoring as an alternative.
However, our technology has some limitations. First, since this is a novel technology, only a single operation was applied. An insufficient number of cases limits the objective evaluation of surgical effect and safety. Second, since the long-term follow-up of the patient is in progress, long-term prognosis, especially the existence of unpredictable potential complications, cannot be presently addressed. Third, this technology was only applied to the PLC injury of the cervical spine. Future studies should apply the technology in the repair of the PLC injury of thoracolumbar segments or patients with minor cervical fractures, to improve the technology under various conditions. To fully understand the implications of this technique, active follow-up and evaluation of our present patient will be maintained. The technology will also be frequently applied to increase the number of cases. Further biomechanical experiments and finite element analysis with this technology are necessary for the future.