C1-2 Fusion Research Articles

Incidence of Congenital Posterior Arch Defects of the Atlas in Chinese Population

To study the incidence of congenital posterior arch defects of the atlas and in combination with other congenital variations in the Chinese population. 1405 images of cervical three-dimensional computed tomography (3D CT) and 1284 images of head and cervical three-dimensional computed tomography angiography (3D CTA) were retrospectively reviewed, including images of 1539 males and 1150 females. These images of cervical 3D CT and head and cervical 3D CTA were obtained in the Department of Radiology of two hospitals, Second and Third People's Hospital of Jingzhou, China, from January 2020 to October 2023. And congenital posterior arch defects of the atlas were classified according to the criteria of Currarino et al. Congenital posterior arch defects of the atlas combined with other congenital variations including occipitalization of the atlas, the ponticulus posticus variation of the vertebral artery groove of the atlas, cervical fusion, and the transversal foramen of the atlas variant were also observed. A total of 2689 subjects were included in this study. The overall prevalence of congenital posterior arch defects of the atlas was 0.74% (20/2689). There was no statistically significant difference in incidence between males (0.78%,12/1539) and females (0.70%,8/1150) (P >0.05). Among all posterior defects, type A and B defects were found in 0.6% (16/2689) and 0.15% (4/2689) cases, respectively. There were no type C, D, and E defects and no anterior arch defects. But in 20 cases of congenital posterior arch defects of atlas, 40%(8/20) combined with other congenital variations including occipitalization of atlas in 4 type A cases, bilateral complete ponticus posticus variation of atlas vertebral groove in one type A case, C2-3 fusion in one type A case, coexistence of unilateral complete ponticulus posticus variation of the vertebral artery groove of the atlas and unilateral unclosed transverse foramen in one type B case, and coexistence of unilateral unclosed transverse foramen in one type A case. The incidence of congenital posterior arch defects of the atlas was low in Chinese population. There was no difference between males and females. Type A and B were the two major defects in Chinese population, and the prevalence of type A and B combined with other congenital cervical variations were higher than those of type C, D, and E.

A screw algorithm for congenital C2-3 fusion with high-riding vertebral arteries: feasibilities and clinical outcomes of five different fixation techniques.

To propose a screw algorithm and investigate the anatomical feasibilities and clinical outcomes of five distinct fixation methods for C2-3 fused vertebra with high-ridding vertebral arteries (VA) (HRVA) when the C2 pedicle screw placement is unfeasible. Thirty surgical patients with congenital C2-3 fusion, HRVA, and atlantoaxial dislocation (AAD) were included. We designed a algorithm for alternative screw implantation into C2-3 fused vertebrae, including C2 pedicle screw with in-out-in (passing VA groove) technique (in-out-in screw), subfacetal screw, translaminar screw, lateral mass screw, C3 pedicle screw. VA diameter and position, C2 and C3 pedicles, superior facets, fused lamina, and fused lateral mass dimensions were evaluated for screw implantation indication. Implant failure, reduction loss, implant placement accuracy were investigated by computed tomography. A total of 5 VAs were identified as distant VAs; a total of 2 VAs were categorized as occlusive VAs. Sufficient dimension of lateral mass and lamina provided the broadest indications for screw implantation, while the distant or occlusive VA provided the most limited indications for in-out-in screw. The indications of five alternative methods ranged from narrowest to widest as follows: in-out-in screw, C3 pedicle screw, subfacetal screw, translaminar screw, lateral mass screw. The translaminar screws and the lateral mass screws increased the probability of implant failure. All patients who received in-out-in screws, C3 pedicle screws, and subfacetal screws achieved fusion. The accuracy ranged from lowest to highest as follows: C3 pedicle screw, lateral mass screw, in-out-in screw, subfacetal screw, translaminar screw. No translaminar screws deviated. The algorithm proved to be a valuable tool for screw selection in cases of C2-3 fused vertebrae with HRVAs. The subfacetal screw, boasting broad indications, a high fusion rate, and exceptional accuracy, stood as the primary preferred alternative.

C2 pedicle screw insertion assisted by mobilization of the vertebral artery in cases with high-riding vertebral artery

ObjectiveTo describe the feasibility, safety and efficacy of mobilization of the vertebral artery for C2 pedicle screws in cases with the high-riding vertebral artery (HRVA). MethodsDuring the period January 2020 to September 2022, fifteen patients underwent posterior occipitocervical fixation in our department. All patients had unilateral HRVA on at least one side that prohibited the insertion of C2 pedicle screws. There were 2 males and 13 females aged 47 ± 11.9 years (range: 17–64 years). After the correction of the vertical dislocation during the operation, the C2 pedicle screw insertion and occipitocervical fixation and fusion were performed using the vertebral artery mobilization technique. A routine three-dimensional reconstructed CT examination was executed to confirm the trajectory of C2 pedicle screws post-operation, and a CT angiography examination was performed when necessary. Neurological function was assessed using the Japanese Orthopedic Association (JOA) scale. The preoperative and postoperative JOA score and the main radiological measurements, including anterior atlantodental interval (ADI), the distance of odontoid tip above Chamberlain line, and clivus-canal angle (CCA), were collected and compared by paired t-test. ResultsAll 15 patients had atlas assimilation, among which 12 patients had C2–C3 fusion (Klippel-Feil syndrome). Mobilization of the HRVA was successfully completed, and C2 pedicle screws were then fulfilled after the vertebral artery was protected. There was no injury to the vertebral artery during the operation. Meanwhile, no severe surgical complications such as cerebral infarction or aggravated neurological dysfunction occurred during the perioperative period. Satisfactory C2 pedicle screw placement and reduction were reached in all 15 patients. All the patients achieved bone fusion 6 months after surgery. No looseness and shift of internal fixation or reduction loss was observed during the follow-up period. Compared to the preoperative, the postoperative JOA score and the main radiological measurements were remarkably improved and statistically significant. ConclusionsC2 pedicle screw insertion assisted by mobilization of the vertebral artery is safe and considerably effective, providing a choice for internal fixation in cases with high-riding vertebral arteries.

Comparative meta-analysis of implant-associated complications and spinal fusion incidence in Goel-Harms technique and posterior С<sub>1</sub>-С<sub>2</sub> transarticular screw fixation per F. Magerl

Transarticular fixation (TAF) of C1–C2 using the F. Magerl method and the Goеl–Harms technique (GHT) are the two most popular ways of forming spondylodesis at the atlantoaxial level. Nevertheless, comparative studies with a high level of evidence have not been published at present.The aim of the study was to conduct a comparative meta‑analysis of the incidence of implant‑associated complications and fusion. The initial search in revealed more than 5,000 abstracts, after applying filters, 202 studies were selected, of which 16 works were included in this study. According to the results of the meta‑analysis, no significant differences were found between the methods of Goel–Harms and F. Magerl in the duration of surgery and intraoperative blood loss, as well as in the frequency of postoperative implant‑associated complications and spinal fusion of C1–C2 vertebrae.

Vertebral Artery Pseudoaneurysm After Extreme Lateral Transcondylar Transodontoid Approach for Clival Chordoma: 2-Dimensional Operative Video

Chordomas can be treated surgically, with radiotherapy, and more recently, chemotherapy. 1,2 A 22-year-old female patient presented with recurrence of a clival chordoma, after subtotal resection at an outside institution 3 months prior. MRI showed a predominantly midline lesion at the craniocervical junction with significant lateral extension eccentric to the left. A 3-staged operation was planned. A redo-endoscopic endonasal transclival transodontoid approach 3-5 was used to resect the midline component, followed by an extreme lateral transcondylar transodontoid approach with transposition of the ipsilateral vertebral artery followed by drilling of the ipsilateral occipital condyle and C1 lateral mass to resect the lateral component, followed by occiput to C3 fusion given the induced craniocervical instability. Careful subperiosteal dissection with preservation of the periosteal sheath overlying the vertebral artery was performed. There was no overt evidence of vertebral artery injury intraoperatively or on immediate postoperative imaging. However, 3 weeks later, the patient presented with blood from the oral/nasal cavity. Computed tomography angiography showed an unexpected left vertebral artery pseudoaneurysm. Pseudoaneurysms can develop after microtears in the muscularis layer. 6-8 Management is based on size, location, and vertebral artery dominance. 9,10 This pseudoaneurysm was coiled. Postcoiling, the patient had left hypoglossal palsy. We demonstrate the step-by-step technique of an extreme lateral transcondylar transodontoid approach for a clival chordoma and the unfortunate complication of a vertebral artery pseudoaneurysm with discussion of its etiology and management options for this potentially devastating complication. The patient consented to the procedure/publication. Institutional Review Board approval not obtained as the patient was deidentified, and no additional risk is posed by the publication of this video.

Evaluation of the Bone Union Occurring Subsequent to C1-2 Fusion Combined With C1 Laminectomy for the Surgical Treatment of Retro-Odontoid Pseudotumor.

Introduction Surgical treatments for retro-odontoid pseudotumors (ROPs) include C1 laminectomies and C1-2 and occipitocervical (OC) fusions. When a C1 laminectomy is combined with a C1-2 fusion, concerns arise regarding an increased risk of pseudarthrosis due to decreased bone grafting space. Extension of the fusion area to the OC region may be considered to ensure an adequate bone graft bed. However, this procedure is associated with a risk of complications. Thus, in this study, we investigated the bone fusion and clinical outcomes of C1-2 fusion combined with a C1 laminectomy. Methods Between January 2017 and December 2022, seven patients with ROPs who had undergone C1-2 fusion combined with a C1 laminectomy were included in the study. All patients were followed up for >1 year. Bone fusion was evaluated by computed tomography (CT) at one year postoperatively, while implant failure was assessed by radiography at the final follow-up. Clinical evaluations included preoperative and one-year postoperative Japanese Orthopaedic Association (JOA) scores and recovery rates. Results This study included five male and two female patients, with an average age of 71.9 years. The average follow-up duration was 3.3 years. The primary anchor choices included the C1 lateral mass screw and the C2 pedicle screw. In one case, the transarticular screw was utilized unilaterally, and in another case, a lamina screw was utilized unilaterally. One year postoperatively, CT revealed bone fusion in three of the seven patients. Fusion occurred at the lateral and median atlantoaxial joints in two cases and one case, respectively. Screw loosening was observed in one case. None of the patients required reoperations. The average JOA recovery rate was 34.6%. Conclusion This surgical technique is useful for stabilizing and decompressing the C1-2 region while preserving mobility at the OC joint. However, further long-term follow-up studies are required.

The effect of C2 screw type on perioperative outcomes and long-term stability after C2-T2 posterior cervical decompression and fusion.

To determine if C2 pedicle versus pars screw type predicts change in fusion status, C2 screw loosening, cervical alignment, and patient-reported outcomes measures (PROMs) after C2-T2 posterior cervical decompression and fusion (PDCF). All adult patients who underwent C2-T2 PCDF for myelopathy or myeloradiculopathy between 2013-2020 were retrospectively identified. Patients were dichotomized by C2 screw type into bilateral C2 pedicle and bilateral C2 pars screw groups. Preoperative and short- and long-term postoperative radiographic outcomes and PROMs were collected. Univariate and multivariate analysis compared patient factors, fusion status, radiographic measures, and PROMs across groups. A total of 159 patients met the inclusion/exclusion criteria (76 bilateral pedicle screws, 83 bilateral pars screws). Patients in the C2 pars relative to C2 pedicle screw group were on average more likely to have bone morphogenic protein (p = 0.001) and four-millimeter diameter rods utilized intraoperatively (p = 0.033). There were no significant differences in total construct and C2-3 fusion rate, C2 screw loosening, or complication and revision rates between C2 screw groups in univariate and regression analysis. Changes in C2 tilt, C2-3 segmental lordosis, C0-2 Cobb angle, proximal junctional kyphosis, atlanto-dens interval, C1 lamina-occiput distance, C2 sagittal vertical axis, C2-7 lordosis, and PROMs at all follow-up intervals did not vary significantly by C2 screw type. There were no significant differences in fusion status, hardware complications, and radiographic and clinical outcomes based on C2 screw type following C2-T2 PCDF. Accordingly, intraoperative usage criteria can be flexible based on patient vertebral artery positioning and surgeon comfort level.

269 Risk Factors for Fusion Failure in Children Undergoing Occipital to C2 Rigid Instrumentation and Fusion

INTRODUCTION: Studies of pediatric occipital-cervical fusions have been limited, and there is substantial variation among surgical constructs with reported failure rates as high as 20%. METHODS: The Pediatric Spine Study Group (PSSG) registry was queried to identify patients </= 21-years-old who had: (1) O-C2 posterior rigid instrumentation and fusion, (2) 2-year clinical and radiographic follow-up, and (3) available post-operative lateral cervical radiograph or CT. Failure was defined as hardware revision surgery >30 days following the index procedure or the presence of screw haloing or breakage on the most recent imaging study. Univariate comparisons were made using Mann-Whitney U-tests, Chi-square tests, and Fisher’s Exact tests followed by multivariable logistic regression. RESULTS: 76 patients were included. The median age at surgery was 9 years (range, 0.2 to 17.2 years), and 51% of the cohort was male. 55% percent of patients had syndromic etiology (41/75), and the most frequent diagnosis was Down Syndrome (28%). Of the 74 patients with complete information, 28/74 (38%) had fusion failure (95% CI, 27%-50%). Rib autographs were used more frequently in patients with successful fusions compared to failures (52% vs 25%; p = 0.04). Multivariable logistic regression determined that patients with rib autograft have a 75% decrease in the odds of failure compared to those without rib autograft (OR = 0.25; 95% CI = 0.08-0.75; p = 0.01). Other variables did not influence the risk for failure. CONCLUSIONS: In this multicenter, international registry study of children undergoing O-C2 rigid instrumentation, fusion failure was seen in 38% of patients, a higher rate than previously reported. Based on this study, the use of structural rib autograft should be considered to reduce fusion failure.

Atlantoaxial facet fixation using cervical facet cage: technical case report and review of the literature.

In 1994, the use of interfacet spacer placement was for joint distraction, reduction, and fusion to supplement atlantoaxial or occipitocervical fixation. Here, we present a unique case of bilateral atlantoaxial interfacet fixation using cervical facet cages (CFC) in a pediatric patient with basilar invagination. In addition, we review the literature on atlantoaxial facet fixation. We present a 12-year-old boy with Wiedemann-Steiner syndrome who presented with multiple episodes of sudden neck jerking, described as in response to a sensation of being shocked, and guarding against neck motion, found to have basilar invagination with cervicomedullary compression. He underwent an occiput to C3 fusion with C1-C2 CFC fixation. We also conducted a literature review identifying all publications using the following keywords: "C1" AND "C2" OR "atlantoaxial" AND "facet spacer" OR "DTRAX." The patient demonstrated postoperative radiographic reduction of his basilar invagination from 6.4 to 4.1mm of superior displacement above the McRae line. There was a 4.5mm decrease in the atlantodental interval secondary to decreased dens retroflexion. His postoperative course was complicated by worsening of his existing dysphagia but was otherwise unremarkable. His neck symptoms completely resolved. We illustrate the safe use of CFC for atlantoaxial facet distraction, reduction, and instrumented fixation in a pediatric patient with basilar invagination. Review of the literature demonstrates that numerous materials can be safely placed as a C1-C2 interfacet spacer including bone grafts, titanium spacers, and anterior cervical discectomy and fusion cages. We argue that CFC may be included in this arsenal even in pediatric patients.

Natural history of craniovertebral abnormalities in a single-center study in 54 patients with Hurler syndrome.

Craniovertebral junction (CVJ) abnormalities are common and well documented in mucopolysaccharidosis type I-Hurler syndrome (MPS IH), often causing severe spinal canal narrowing. However, the requirement for surgical decompression and/or fusion is uncommon. Although hematopoietic cell transplant (HCT) has been shown to prolong the lives of patients with MPS IH, its effect in halting or reversing musculoskeletal abnormalities is less clear. Unfortunately, there are currently no universal guidelines for imaging or indication for surgical interventions in these patients. The goal of this study was to track the progression of the CVJ anatomy in patients with MPS IH following HCT, and to examine radiographic features in patients who needed surgical intervention. Patients with MPS IH treated at the University of Minnesota with allogeneic HCT between 2008 and 2020 were retrospectively reviewed. Patients who underwent CVJ surgery were identified with chart review. All MPS IH cervical scans were examined, and the odontoid retroflexion angle, clivoaxial angle (CXA), canal width, and Grabb-Oakes distance (pB-C2) were measured yearly for up to 7 years after HCT. Longitudinal models based on the measurements were made. An intraclass correlation coefficient was used to measure interrater reliability. Nine children without MPS IH were examined for control CVJ measurements. A total of 253 cervical spine MRI scans were reviewed in 54 patients with MPS IH. Only 4 (7.4%) patients in the study cohort required surgery. Three of them had posterior fossa and C1 decompression, and 1 had a C1-2 fusion. There was no statistically significant difference in the spinal parameters that were examined between surgery and nonsurgery groups. Among the measurements, canal width and CXA varied drastically in patients with different neck positions. Odontoid retroflexion angle and CXA tended to decrease with age. Canal width and pB-C2 tended to increase with age. Based on the data, the authors observed an increase in canal width and pB-C2, whereas the CXA and odontoid retroflexion angle became more acute as the patients aged after HCT. The longitudinal models derived from these data mirrored the development in children without MPS IH. Spinal measurements obtained on MR images alone are not sufficient in identifying patients who require surgical intervention. Symptom monitoring and clinical examination, as well as pathological spinal cord changes on MRI, are more crucial in assessing the need for surgery than is obtaining serial imaging.

Biomechanical evaluation of the novel assembled internal fixed system in C2–C3 anterior cervical discectomy and fusion: a finite element analysis

BackgroundTo analyze and compare the biomechanical characteristics of the new combined cervical fusion device (NCCFD) and the traditional cage-plate construct (CPC) to ascertain its effectiveness in anterior cervical discectomy and fusion (ACDF) using finite element analysis.MethodsA finite element model of the cervical spine, inclusive of the occipital bone was created and validated. In the ACDF model, either CPC or NCCFD was implanted at the C2–C3 segment of the model. A pure moment of 1.0 Nm combined with a follower load of 50 N was directed onto the superior surfaces of the occipital bone to determine flexion, extension, lateral bending (left and right), and axial rotation (left and right). The range of motion (ROM), stress distribution at the bone-implant interface, and facet joint forces were investigated and compared between CPC and NCCFD systems.ResultThe results showed that the ROMs of the fused levels in both models were nearly zero, and the motions of the unfused segments were similar. In addition, the maximum displacement exhibited nearly identical values for both models. The maximum stress of NCCFD screws in lateral bending and rotational conditions is significantly higher than that of the CPC, while the NCCFD model’s maximum stress remains within an acceptable range. Comparing the maximum fusion stress, it was found that the CPC experiences much lower fusion stress in anterior flexion and extension than the NCCFD, with no significant difference between the two in lateral bending and rotational states. Stress on the cage was mainly concentrated on both sides of the wings. Comparing the maximum IDP in the CPC and NCCFD, it was observed that maximum stresses rise in extension and lateral bending for both models. Lastly, stress distributions of the facet joints were generally similar across the two devices.ConclusionNCCFD not only provides the same level of biomechanical stability as CPC but also avoids postoperative complications associated with uneven force damage to the implant. The device offers a novel surgical alternative for ACDF in C2–C3 level.

Functional and radiological outcomes following craniovertebral junction surgery.

Craniovertebral junction (CVJ) pathologies include atlantoaxial instability/deformities resulting in myelopathy, respiratory failure, and even death. Here, we describe the indications, preoperative planning, and intra-operative/postoperative complications following surgical management of CVJ anomalies. A prospective analysis of 34 patients with CVJ pathology was evaluated between 2015 and 2022. Their various etiologies included atlantoaxial instability, trauma, tuberculosis, Down's syndrome, Morquio syndrome, os odontoideum, and atlantoaxial abnormalities. Clinical outcomes were assessed using the American spinal injury association (ASIA) impairment scale score and Benzel's modified Japanese Orthopedic Association (mJOA) score. Surgical assessments included length of hospital stay, operative time, blood loss, and intraoperative postoperative complications. Radiological parameters included fusion (i.e., implant loosening/implant failure), preoperative/ postoperative atlanto-dens interval (ADI), clivus canal angle (CCA), and space available for cord (SAC). Five patients were managed conservatively, while 29 patients had surgery. Operations included occipitocervical fusion (14 patients), C1-2 fusion (10 patients), C1-2 transarticular screw fixation (four patients), and one patient underwent anterior corpectomy decompression/fusion. Seven patients had vertebral artery anomalies, and 13 patients had atlantoaxial abnormalities. At the final follow-up, atlantoaxial instability (i.e., mean preoperative ADI of 6.6 ± 2.3 mm) was restored to 4.2 ± 0.6 mm, significant cord compression (i.e., with mean SAC of 8.3 ± 2.9 mm) was relieved to 17.2 ± 1.6 mm, and the mean preoperative CCA (i.e., 130.2 ± 15.3) was improved to 143.3 ± 8.3°. There was also a statistically significant improvement in the ASIA scale and mJOA score. Surgical management of CVJ abnormalities requires expertise and meticulous planning to avoid devastating complications such as wound dehiscence and catastrophic vertebral artery injury.

Genetically encoded phosphatidylserine biosensor for in vitro, ex vivo and in vivo labelling

BackgroundThe dynamics of phosphatidylserine in the plasma membrane is a tightly regulated feature of eukaryotic cells. Phosphatidylserine (PS) is found preferentially in the inner leaflet of the plasma membrane. Disruption of this asymmetry leads to the exposure of phosphatidylserine on the cell surface and is associated with cell death, synaptic pruning, blood clotting and other cellular processes. Due to the role of phosphatidylserine in widespread cellular functions, an efficient phosphatidylserine probe is needed to study them. Currently, a few different phosphatidylserine labelling tools are available; however, these labels have unfavourable signal-to-noise ratios and are difficult to use in tissues due to limited permeability. Their application in living tissue requires injection procedures that damage the tissue and release damage-associated molecular patterns, which in turn stimulates phosphatidylserine exposure.MethodsFor this reason, we developed a novel genetically encoded phosphatidylserine probe based on the C2 domain of the lactadherin (MFG-E8) protein, suitable for labelling exposed phosphatidylserine in various research models. We tested the C2 probe specificity to phosphatidylserine on hybrid bilayer lipid membranes by observing surface plasmon resonance angle shift. Then, we analysed purified fused C2 proteins on different cell culture lines or engineered AAVs encoding C2 probes on tissue cultures after apoptosis induction. For in vivo experiments, neurotropic AAVs were intravenously injected into perinatal mice, and after 2 weeks, brain slices were collected to observe C2-SNAP expression.ResultsThe biophysical analysis revealed the high specificity of the C2 probe for phosphatidylserine. The fused recombinant C2 proteins were suitable for labelling phosphatidylserine on the surface of apoptotic cells in various cell lines. We engineered AAVs and validated them in organotypic brain tissue cultures for non-invasive delivery of the genetically encoded C2 probe and showed that these probes were expressed in the brain in vivo after intravenous AAV delivery to mice.ConclusionsWe have demonstrated that the developed genetically encoded PS biosensor can be utilised in a variety of assays as a two-component system of C2 and C2m2 fusion proteins. This system allows for precise quantification and PS visualisation at directly specified threshold levels, enabling the evaluation of PS exposure in both physiological and cell death processes.

An Underwater Dense Small Object Detection Model Based on YOLOv5-CFDSDSE

Underwater target detection is a key technology in the process of exploring and developing the ocean. Because underwater targets are often very dense, mutually occluded, and affected by light, the detection objects are often unclear, and so, underwater target detection technology faces unique challenges. In order to improve the performance of underwater target detection, this paper proposed a new target detection model YOLOv5-FCDSDSE based on YOLOv5s. In this model, the CFnet (efficient fusion of C3 and FasterNet structure) structure was used to optimize the network structure of the YOLOv5, which improved the model’s accuracy while reducing the number of parameters. Then, Dyhead technology was adopted to achieve better scale perception, space perception, and task perception. In addition, the small object detection (SD) layer was added to combine feature information from different scales effectively, retain more detailed information, and improve the detection ability of small objects. Finally, the attention mechanism squeeze and excitation (SE) was introduced to enhance the feature extraction ability of the model. This paper used the self-made underwater small object dataset URPC_UODD for comparison and ablation experiments. The experimental results showed that the accuracy of the model proposed in this paper was better than the original YOLOv5s and other baseline models in the underwater dense small object detection task, and the number of parameters was also reduced compared to YOLOv5s. Therefore, YOLOv5-FCDSDSE was an innovative solution for underwater target detection tasks.

Current Concepts in the Treatment of Traumatic C2 Vertebral Fracture : A Literature Review.

The integrity of the high cervical spine, the transition zone from the brainstem to the spinal cord, is crucial for survival and daily life. The region protects the enclosed neurovascular structure and allows a substantial portion of the head motion. Injuries of the high cervical spine are frequent, and the fractures of the C2 vertebra account for approximately 17-25% of acute cervical fractures. We review the two major types of C2 vertebral fractures, odontoid fracture and Hangman's fracture. For both types of fractures, favorable outcomes could be obtained if the delicately selected conservative treatment is performed. In odontoid fractures, as the most common fracture on the C2 vertebrae, anterior screw fixation is considered first for type II fractures, and C1-2 fusion is suggested when nonunion is a concern or occurs. Hangman's fractures are the second most common fracture. Many stable extension type I and II fractures can be treated with external immobilization, whereas the predominant flexion type IIA and III fractures require surgical stabilization. No result proves that either anterior or posterior surgery is superior, and the surgeon should decide on the surgical method after careful consideration according to each clinical situation. This review will briefly describe the basic principles and current treatment concepts of C2 fractures.

Treatment of unstable C1 semi-ring fractures with direct C1 pedicle screw fixation using a navigational template: A case report and literature review.

Because of the risk of C1 to C2 instability, which would reduce the mobility of the occipito-atlanto-axis articulation, unstable C1 semi-ring fractures are typically treated with C1 to C2 or C0 to C2 fusion. The vertebral artery and spinal cord are at risk of harm during the installation of C1 pedicle screws. There is a need for a method that can maintain the occipito-atlanto-axis articulation's mobility and increase the safety of C1 pedicle screw fixation, particularly for surgeons who have less experience inserting C1 pedicle screws freehand. A 45-year-old man who had suffered a severe fall from a height of 2.5 m presented with pain in his cervical spine. Magnetic resonance imaging and computed tomography were used to diagnose unstable atlas fractures. According to radiographic studies, the patient had a unilateral anterior and posterior arch fracture (semi-ring fracture, Landells type II), as well as fractures and transverse ligament avulsion at the attachment site. We fixed the C1 directly with a pedicle screw using a navigational template. Both during and after the operation, there were no connected complications. Imaging at 12 months after surgery demonstrated that the fracture had united. The average visual analog scale score decreased from 8 before surgery to 2. In particular for surgeons with less experience placing freehand C1 pedicle screws, direct C1 pedicle screw fixation with the aid of a navigational template was a good option because it can preserve the mobility of the occipito-atlanto-axis articulation and improve the safety of C1 pedicle screw.

Incidences, causes and risk factors of unplanned reoperation within 30days of craniovertebral junction surgery: a single-center experience.

To investigate the incidences, causes, and risk factors for unplanned reoperation within 30days of craniovertebral junction (CVJ) surgery. From January 2002 to December 2018, a retrospective analysis of patients who underwent CVJ surgery at our institution was conducted. The demographics, history of the disease, medical diagnosis, approach and type of operation, surgery duration, blood loss, and complications were recorded. Patients were divided into the no-reoperation group and the unplanned reoperations group. Comparison between two groups in noted parameters was analyzed to identify the prevalence and risk factors of unplanned revision and a binary logistic regression was performed to confirm the risk factors. Of 2149 patients included, 34(1.58%) required unplanned reoperation after the initial surgery. The causes for unplanned reoperation contained wound infection, neurologic deficit, improper screw placement, internal fixation loosens, dysphagia, cerebrospinal fluid leakage, and posterior fossa epidural hematomas. No statistical difference was found in demographics between two groups (P > 0.05). The incidence of reoperation of OCF was significantly higher than that of posterior C1-2 fusion (P = 0.002). In terms of diagnosis, the reoperation rate of CVJ tumor patients was significantly higher than that of malformation patients, degenerative disease patients, trauma patients, and other patients (P = 0.043). The binary logistic regression confirmed that different disease, fusion segment (posterior) and surgery time were independent risk factors. The unplanned reoperation rate of CVJ surgery was 1.58% and the major causes were implant-related failures and wound infection. Patients with posterior occipitocervical fusion or diagnosed with CVJ tumors had an increased risk of unplanned reoperation.

C1-2 Fusion in Atlantoaxial Dislocation and Basilar Invagination with and without Chiari Malformation: Clinical/Radiological and Craniometric Results

Patients with Chiari malformation (CM) associated with atlantoaxial dislocation (AAD) and basilar invagination (BI) may present with a small posterior cranial fossa, but data on the volumetric analysis are lacking. Additionally, whether additional foramen magnum decompression (FMD) is needed together with atlantoaxial fusion remains controversial. This study evaluated the volumetric alterations of the posterior cranial fossa in these patients and analyzed the radiological and clinical outcomes after posterior C1-C2 reduction and fixation plus C1 posterior arch resection. Thirty-two adult CM patients with AAD and BI (CM-AAD/BI group) and 21 AAD and BI patients without CM (AAD/BI-only group) who received posterior atlantoaxial fusion plus C1 posterior arch resection were retrospectively studied. The clinical and radiological outcomes and volumetric measurements of the posterior cranial fossa were evaluated. The majority of CM-AAD/BI patients (94%) improved clinically and radiologically at 12mo postoperatively, and none required additional FMD. Morphological analysis revealed a significant reduction in the bony posterior cranial fossa volumes of the CM-AAD/BI group (P<0.01) and the AAD/BI-only group (P<0.01) relative to those of the CM group. No significant differences were observed between the CM-AAD/BI and AAD/BI groups. Compared with patients with simple CM, patients with AAD/BI with or without CM demonstrated a considerably and equally reduced bony posterior cranial fossa volume. No additional FMD is needed in the treatment of CM-AAD/BI patients after posterior reduction and fusion plus C1 posterior arch resection.

662 Navigation in Cervical Spine Surgery: A Review of Past and Current Uses

INTRODUCTION: The last two decades in spine surgery have resulted in an expansion of innovation and new enabling technologies. Within those new developments, spinal navigation has been adopted widely. Nonetheless, the use in the cervical spine remains a less explored METHODS: A scoping review of the literature was performed via PubMed. Limited to English and no date limit. Different search queries with MesH terms such as “Surgical Navigation Systems" "Spatial Navigation”, "Surgery, Computer-Assisted”, "Cervical Vertebrae", “cervical spine” with combination of OR and AND. Inclusion criteria: articles discussing the use of any navigation platform in the cervical spine. RESULTS: A total of 365 articles were found. After title and abstract selection, a total of 87 articles were reviewed. All the articles were retrospective. A total of 2101 patients underwent cervical procedures with spinal navigation, 54% were male. Average age of the cohort was 53.6 years. The Stealth navigation system (Medtronic) was the most commonly used followed by BrainLab and the large majority used CT based navigation. Degenerative conditions were the most common followed by trauma. There were 1872 total screws placed under navigation. Most common use for navigation was placement of cervical pedicle screws with a range of pedicle screw accuracy from 76.5-97.1%. The most common level for misplacement was C4. Additional uses include occipital and C1-2 fusion, corpectomies, transoral, transnasal approaches, and tumor localization. Direct complications from screw placement: C5 palsy, vertebral artery injury and dural tears. Mean follow up was 22.6 months. CONCLUSIONS: Spinal navigation in the cervical spine remains an understudied field. The current reports show good accuracy for placement of cervical pedicle screws, with minimal complications but other uses within the cervical spine remain somewhat limited. Given our evolving understanding of cervical pathology

Central or axial atlantoaxial dislocation and craniovertebral junction alterations: a review of 393 patients treated over 12 years.

The authors reviewed their scientific publications and updated their clinical material obtained over the last 12 years for cases of central or axial atlantoaxial dislocation (CAAD) identified in the presence of craniovertebral musculoskeletal and/or neural alteration(s). The management implications of diagnosing and treating CAAD are highlighted. During a 12-year period, CAAD was diagnosed in 393 patients with craniovertebral junction-related musculoskeletal and neural alterations who underwent atlantoaxial fixation. No bone decompression was done. All CAAD-related craniovertebral junction structural changes were identified to have a naturally protective role. Hence, in this paper the term "craniovertebral alterations" is used for "craniovertebral junction anomalies" and the term "Chiari formation" is used instead of the commonly used term "Chiari malformation." The major radiological diagnosis was determined either singly or in cohort with one or more of other so-called pathological entities that included Chiari formation (367 cases), syringomyelia with Chiari (306 cases), idiopathic syringomyelia (12 cases), type B basilar invagination (147 cases), bifid arch of the atlas (9 cases), assimilation of the atlas (119 cases), C2-3 fusion (65 cases), Klippel-Feil alteration (4 cases), and dorsal kyphoscoliosis (15 cases). The follow-up period ranged from 6 to 155 months. Clinical improvement was observed in all patients. Understanding and treating CAAD may have significant implications in the surgical treatment of a number of clinical entities. The gratifying clinical outcomes obtained in patients after atlantoaxial fixation, without any type of decompression involving bone or soft-tissue resection, consolidate the concept that atlantoaxial instability has a defining role in the pathogenesis.