Surgical Intervention for Instability of the Craniovertebral Junction

Biomechanical comparison of anterior axis-atlanto-occipital transarticular fixation and anterior atlantoaxial transarticular fixation after odontoidectomy: A finite element analysis

Background: Anterior axis-atlanto-occipital transarticular fixation (AAOF) and anterior atlanto-axial transarticular fixation (AAF) are two common anterior screw fixation techniques after odontoidectomy, but the biomechanical discrepancies between them remain unknown. Objectives: To investigate the biomechanical properties of craniovertebral junction (CVJ) after odontoidectomy, with AAOF or AAF. Methods: A validated finite element model of the intact occipital-cervical spine (from occiput to T1) was modified to investigate biomechanical changes, resulting from odontoidectomy, odontoidectomy with AAOF, and odontoidectomy with AAF. Results: After odontoidectomy, the range of motion (ROM) at C1-C2 increased in all loading directions, and the ROM at the Occiput-C1 elevated by 66.2%, 57.5%, and 41.7% in extension, lateral bending, and torsion, respectively. For fixation models, the ROM at the C1-C2 junction was observably reduced after odontoidectomy with AAOF and odontoidectomy with AAF. In addition, at the Occiput-C1, the ROM of odontoidectomy with AAOF model was notably lower than the normal model in extension (94.9%), flexion (97.6%), lateral bending (91.8%), and torsion (96.4%). But compared with the normal model, in the odontoidectomy with AAF model, the ROM of the Occiput-C1 increased by 52.2%, -0.1%, 92.1%, and 34.2% in extension, lateral bending, and torsion, respectively. Moreover, there were no distinctive differences in the stress at the screw-bone interface or the C2-C3 intervertebral disc between the two fixation systems. Conclusion: AAOF can maintain CVJ stability at the Occiput-C1 after odontoidectomy, but AAF cannot. Thus, for patients with pre-existing atlanto-occipital joint instability, AAOF is more suitable than AAF in the choice of anterior fixation techniques.

Severe dysphagia after a posterior cervical spine fusion at the C1–C3 level and its improvement after correction surgery for malalignment: a case report

Background

The development of dysphagia and trismus following posterior C1–C3 fusion is rare compared to occipitocervical fusion, and there are very few reports in the literature.

Case presentation

A 75-year-old Thai man who had an extradural tumor at the C1/C2 level developed severe dysphagia and trismus immediately after tumor resection and C1–C3 fusion. During the surgery for malalignment correction, the C1–C2 screws were re-aligned into an increased lordotic position. The symptoms resolved immediately post-surgery.

Conclusions

Short upper cervical fusion can produce trismus and dysphagia in a relatively flexed position. Preoperative planning should be individualized based on the patient’s resting neutral alignment to prevent complications.

Modification of Wright’s Technique for C2 Translaminar Screws Based on Medical Imaging Analysis

Background: To describe and explain the improvement of Wright C2 transforaminal screw fixation technique. Methods: 23 male patients and 10 female patients (a total of 33 patients, average age of 55 years) were implanted with lamina screws on one side or both sides by improved technique. Adopt improved technology, there is a simple hole in the middle of the lateral brain plate, and the screw can be seen directly to prevent the spine from being invaded. Results: With the improved technique, 169 minutes (90–210 minutes) is the average operation time, and 136 ml (80–420 minutes) is the estimated average blood loss. Average length of 26.5 mm (range 24–30) plate screws. After an average follow-up of 12.4 (1.5–30) months, all patients achieved good clinical outcomes. Conclusions: To modify the Wright’s technique, an additional unicortical “hole” was in the middle of the backplane. Through this improved technique, the screw can be directly seen to be inserted into the dorsal cortex of the lamina, thereby reducing the risk of invading the spinal canal and shortening the operation time.

Suitability of the Subaxial Cervical Laminae for Laminar Screws in the Pediatric Population: A Radiologic Anatomical Study

INTRODUCTION

The laminar screw method was popularized during recent years. Since no data exist in the literature on its suitability for subaxial levels in the pediatric population, a radiologic anatomical study was planned to evaluate the suitability of the laminae for laminar screws in children.

METHODS

The laminar thicknesses from C3 to C7 were measured in axial sections in 120 pediatric patients using computed tomography. The patients were divided into 3 age-groups: ages 4-6, 7-9, and 10-12. Each age-group consisted of 20 boys and 20 girls. The suitability of the laminae was evaluated for 3.5-mm-thick commercially available screws and also for the 3-mm screws that could be produced in the future. If the height of the base of the spinous process is ≥ 9 mm, the segment was accepted as suitable for the bilateral screw, and ≥5 mm is for the unilateral screw. Additionally, laminar thickness and length were measured for possible short screws longer than 15 mm in the laminae that were distally thin but proximally thick.

RESULTS

The C4 and C5 levels had the thinnest (2.77 ± 0.6 mm and 2.81 ± 0.6 mm, respectively) and C7 had the thickest laminae (4.66 ± 0.6 mm) in all age-groups. No significant differences were found between boys and girls and right and left laminae. According to the age-groups, an increase in laminar thickness was possible by growing, but only C7 laminae thickness was statistically different between 10-12 and 4-6 age-groups (p < 0.001). The last rate of the suitability was 9.1% for the 3.5-mm-thick screws and 13.75% for the 3-mm-thick screws after deletion of the bilateral insertion due to the short base of the spinous process and adding the possible short screws in the distally thin but proximally thick laminae. The rates increased with age, but the only statistically significant difference was found between 4-6- and 10-12-year-old age-groups (p < 0.001).

CONCLUSIONS

Laminar screws may be suitable for some levels of C7, C6, and C3 even in the young pediatric population. The use of thinner screws (3 mm) may increase the suitability rate. Therefore, laminar screw choice may be considered as a salvage method in pediatric patients, and all laminae may be evaluated individually for suitability. This study did not evaluate the safety and efficacy of the method in children, and these issues must be studied further.

Additional Surgical Method Aimed to Increase Distractive Force during Occipitocervical Stabilization : Technical Note

OBJECTIVE

Craniovertebral junctional anomalies constitute a technical challenge. Surgical opening of atlantoaxial joint region is a complex procedure especially in patients with nuchal deformity like basilar invagination. This region has actually very complicated anatomical and functional characteristics, including multiple joints providing extension, flexion, and wide rotation. In fact, it is also a bottleneck region where bones, neural structures, and blood vessels are located. Stabilization surgery regarding this region should consider the fact that the area exposes excessive and life-long stress due to complex movements and human posture. Therefore, all options should be considered for surgical stabilization, and they could be interchanged during the surgery, if required.

METHODS

A 53-year-old male patient applied to outpatients' clinic with complaints of head and neck pain persisting for a long time. Physical examination was normal except increased deep tendon reflexes. The patient was on long-term corticosteroid due to an allergic disease. Magnetic resonance imaging and computed tomography findings indicated basilar invagination and atlantoaxial dislocation. The patient underwent C0-C3-C4 (lateral mass) and additional C0-C2 (translaminar) stabilization surgery.

RESULTS

In routine practice, the sites where rods are bound to occipital plates were placed as paramedian. Instead, we inserted lateral mass screw to the sites where occipital screws were inserted on the occipital plate, thereby creating a site where extra rod could be bound. When C2 translaminar screw is inserted, screw caps remain on the median plane, which makes them difficult to bind to contralateral system. These bind directly to occipital plate without any connection from this region to the contralateral system. Advantages of this technique include easy insertion of C2 translaminar screws, presence of increased screw sizes, and exclusion of pullout forces onto the screw from neck movements. Another advantage of the technique is the median placement of the rod; i.e., thick part of the occipital bone is in alignment with axial loading.

CONCLUSION

We believe that this technique, which could be easily performed as adjuvant to classical stabilization surgery with no need for special screw and rod, may improve distraction force in patients with low bone density.

"Direct vision" operation of posterior atlantoaxial transpedicular screw fixation for unstable atlantoaxial fractures: A retrospective study

BACKGROUND

The posterior screw fixation in atlas via posterior arch and lateral mass, also called C1 "pedicle" screw, combined with C2 pedicle screw fixiation has shown better biomechanical stability in unstable atlantoaxial fractures. However, its popularization has to fulfill the limitation imposed by anatomical characteristics. The aim of this study was to explore the manipulation, effect, and safety of the atlantoaxial transpedicular screw fixation under "direct vision" for the treatment of unstable atlantoaxial fracture.

METHODS

All the patients diagnosed with unstable atlantoaxial fracture, who received surgery treatment of C1,C2 internal fixation from January 2012 to December 2014 were reviewed. Only these patients that were diagnosed with atlantoaxial unstability secondary to trauma and were treated with atlantoaxial transpedicular screw fixation under "direct vision" and iliac autograft were included. The safety of transpedicular screw placement, postoperative outcome, atlantoaxial stability, autograft fusion, and complications was observed and analyzed retrospectively. The pain visual analog scale (VAS) and the Japanese Orthopedic Association (JOA) score were used as surgical curative effect evaluation standards.

RESULTS

We reviewed a total of 92 patients diagnosed with unstable atlantoaxial fracture, who received surgery treatment of C1,C2 internal fixation from January 2012 to December 2014, and 87 patients were treated with atlantoaxial transpedicular screw fixation under "direct vision" and were included this analysis. A total of 306 transpedicular screws in atlas and axis were placed successfully. All cases were followed-up >12 months. The overall breach rate was 11.36%. None of the breaches resulted in new-onset neurological sequela. The neurological status in cases with bilateral upper extremities numbness and lower extremities weakness had improved after surgery. At the latest follow-up, the neck VAS and JOA scores were significantly improved (P < .01) than those preoperatively. No cases demonstrated implantation failure and bone graft absorption on the postoperative x-ray films and CT scans.

CONCLUSION

Atlantoaxial transpedicular screw fixation under "direct vision" and iliac autograft for the treatment of unstable atlantoaxial fracture has shown simple manipulation and efficient performance. Thus, the technique of C1-C2 fixation is feasible in treating unstable atlantoaxial fracture.

Surgical Intervention for Unstable Craniovertebral Junction Anomalies with Narrow C2 Pedicle

OBJECTIVE

We sought to investigate and report a novel surgical technique of screws insertion and posterior surgical reduction, as well as explore its clinical results.

METHODS

From September 2008 to September 2012, we treated 41 cases of unstable craniovertebral junction anomalies with a narrow C₂ pedicle at our department. All patients underwent "posterior reduction and internal fixation of the occipital bone with superior or inferior articular process of C₂ and lateral mass of C₃ on the narrowed C₂ pedicle side-for non-narrowed C₂ pedicle side, the screw was only inserted into C₂ pedicle without extending the fixation to C₃ vertebrae-using a titanium screw-rod (plate) fixation system." The preoperative and postoperative atlantodens interval, Chamberlain line, McRae line, and cervicomedullary angle were all measured. In addition, the preoperative and postoperative Japanese Orthopedic Association score was used to evaluate the cervical myelopathy.

RESULTS

A total of 134 screws were inserted into the C₂ pedicle (30 screws), superior (35 screws) or inferior (17 screws) articular process of C₂, and lateral mass of C₃ (52 screws). There was a significant statistical difference between the preoperative and postoperative results in the reduction of the odontoid process, decompression of the upper cervical spinal cord and medulla, as well as the improvement of neurologic functions (P < 0.05). All patients have exhibited a major neurologic improvement and solid bony fusion.

CONCLUSION

This novel surgical technique is safe, feasible, and effective for the treatment of unstable craniovertebral junction anomalies with a narrow C₂ pedicle.