Cervical pedicle screws fixation treatment the atlantoaxial instability of axis burst fractures

the and This study was to evaluated the clinical outcomes of axis burst fractures had C1C3 pedicles screws fixation treatment. From June to 2018, 45 patients with axis fractures were enrolled in this study; 23 patients was odontoid underwent C1C2 pedicles screws fixation, and 21 patients was odontoid combine body fractures had C1C3 pedicles screws fixation. The clinical outcomes of pain relief (visual analog scale, VAS), functional disability (neck disability index, NDI) were recorded at baseline and at the final follow-up. CT radiographs

3 traumatic spondylolisthesis of axial fractures. The atlantoaxial instable of axis burst fractures can be managed with C1-C3 pedicles screws fixation.

Background
The atlantoaxial complex bears approximately 50% of rotary motion and 12% of flexion and extension movement of the cervical spine. [1][2][3][4] The atlantoaxial joint was superior articular processes of C2 articulate with the inferior articular process of C1, which allow for rotation around the dens. Axis (C2) is a unique vertebra in that it serves as the transition from the upper cervical spine to the lower cervical spine. [5,6] However, the stability of atlantoaxial complex relies solely on the atlantoaxial joint and the transverse ligament. Then, any injury of structure above may cause atlantoaxial instability, which was common in the odontoid fractures and pedicles fractures of axis, as well as axial body fractures. [7][8][9][10] As an process of axis, odontoid fractures are very common, accounting for 18 to 20% of cervical injuries, of which 65 to 74% are type II fractures of Anderson and D'Alonzo classification. Type II fractures involve the base of the odontoid and do not extend into the C2 body and unstable associated with a nonunion rate of at least 32% with nonoperative treatment. [11][12][13] Odontoid fractures can causes the atlantoaxial instability, which may cause neck pain and stiffness, activity limitation, and progressive compression of the spinal cord. [14,4,15] As another special fractures of axis, Hangman's fractures was the pedicles fractures of C2 which may led to traumatic spondylolisthesis of the axis. [16,17] Levin and Edwards classified the C2 pedicles fractures into four types, and unstable fractures indicated for surgery. [18][19][20] Therefore, recovering normal anatomical position within a short period of time and maintaining its stability are needed for the treatment of atlantoaxial instability to prevent further spinal cord injury.
Unlike odontoid fractures and hangman's fractures, axial body fractures are uncommon 4 and have a variety of presentations. Although some axial fractures can be healed with nonoperative management, sequelae of varying degrees of nuchal pain because of malalignment and osteoarthrosis of the atlantoaxial joint were common. [10,19] Then, the current trend is surgical treatment in patients to align and stabilize the upper cervical spine protecting the neural elements. Due to axis specificity in structure and position, the axial body fractures still present a challenge for spinal surgeon. However, there are little paper about it in literature. The purpose of this study was to evaluate the clinical outcomes and efficacy of cervical pedicle screws fixation in the treatment of atlantoaxial instability of axis burst fractures.

Materials And Methods
From June 2014 to July 2018, 56 axis fractures patients with neurologically intact were enrolled in this study. All patients were diagnosed on the basis of clinical symptoms, Xrays of the cervical spine, computer tomography (CT), and magnetic resonance imaging (MRI). All patients were categorized into two groups, 35 patients was odontoid fractures or pedicle fractures were underwent C1C2 pedicles screws fixation (C1C2 group, included 13 men and 8 women with an average age of 38.74 ± 9.65 years), and 21 patients was axis body fractures had C1C3 pedicles screws fixation (C1C3 group, included 9 men and 6 women with an average age of 39.28 ± 7.36 years). The inclusion criteria were odontoid type II and type III fractures, C2 pedicle fractures, odontoid combine hangman fractures or body fractures; the . Exclusion criteria included pathologic conditions of the cervical spine (trauma, tumor, or infection). The injury times were 3.56 ± 1.73 day in C1C2 patients, and 3.14 ± 1.62 days in C1C3 patients. There were no significant difference among three group in age and sex distribution, older and the pain history (P > 0.05).

Surgical procedures
After general anesthesia, patient in the prone position. Based on the nature of the C2 fracture, skull traction was performed and preliminary fracture reduction was achieved by maximal cervical flexion or extension in accordance with the direction of fracture displacement. C1, C2, and C3 pedicle screw insertion was performed through the posterior approach as previously described. [21,22,4] To make sure that the screw and bone were appropriately fixed, X-ray and CT scans were performed. Finally, the wound was rinsed and the incisions closed. Patients were allowed to walk with a soft cervical collar at least four weeks post-operatively.

Critical of clinical outcomes
Before surgery and at the one year follow-up, operation times, blood loss, hospital stays, pain relief (visual analog scale, VAS), functional disability (neck disability index, NDI) were used to evaluate patient function. Furthermore, postoperative radiographs, CT, and MRI scans of the cervical spine were obtained for all patients and bone fusion was used as a means of radiological assessment.

Statistical analysis
All measurements were performed by a single observer and are expressed as means ± SD.
Using the SPSS 17.0 statistics software, classic t-test and chi-square test were performed.

6
There was no intraoperative death in this series. In ends 47 cases had follow-up at least one year and 9 cases lost, and the follow-up rate was 82.9% (29/35)

Discussion
Axis body fracture, as well as odontoid and pedicle fractures, may cause atlantoaxial instability which may cause neck pain and stiffness, activity limitation, and progressive compression of the spinal cord. [23,24] Atlantoaxial instability caused by C2 fractures need surgical reduction and stabilization to limit the anterior displacement of atlas effectively and enhance the atlantoaxial sagittal stability to prevent further spinal cord injury. [25,14] Because of the anatomical peculiarity of the axis and the complexity of injury pathology, clinical management of the axis fractures was hard work for spine surgeon. [15] Among the treatment of axis fractures, the posterior pedicles screws fixation was preferred for its relative simple exposure with no major vascular and visceral structures. According to the data of this series, cervical pedicles screw fixation was safely performed in all patients, and there were no complications of nerve and vascular injury in this study cases.
The key to the surgical treatment of atlantoaxial instability caused by axis fractures is to reconstruct the axis structures. [20,26,5] The pedicle screw had the advantage not only at the solid fixation for bone fusion, but also at the active manipulation and reduction of atlantoaxial subluxation. C1 screws combined with separate instrumentation of C2 screws allow for the active manipulation and reduction in atlantoaxial luxation or subluxation.
8 [27,16] In the situation of C2 body fractures and pedicle fractures, C3 pedicle screws was inserted in this series. C3 pedicle screws combined with C1 pedicle screws or lateral mass screw can work as a thoracolumbar spine pedicle screws fixation system and have shown obvious superiority in reduction the C2 body fractures. [28,29]

Conclusion
Cervical pedicle screws fixation was effective and safe procedures in the treatment of 9 traumatic spondylolisthesis of axial fractures. The atlantoaxial instable of axis burst fractures can be managed with C1-C3 pedicles screws fixation.

Ethical approval and consent to participate
This study was approved by the hospital ethics committee of the First People's Hospital of Zhaoqing, Zhaoqing City, Guangdong Province, and all patients signed had informed consent.

Consent for publication
Author Denglu Yan, Zaiheng Zhang, and Zhi Zhang all agree to publication.

Availability of data and materials
The datasets are available under reasonable request.

Competing interests
Author Denglu Yan, Zaiheng Zhang, and Zhi Zhang declare that they have no conflict of interest.

Funding
Not applicable of funding on this work.