C2 Pedicle Screw Research Articles

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.

Improving C1 Pedicle Screw Placement for Atlantoaxial Instability with Ultrasonic Bone Burr Assistance

This study aims to evaluate the safety and efficacy of the ultrasonic bone burr (UBB) in facilitating C1 pedicle screw placement for atlantoaxial instability (AAI) treatment, compared to the conventional high-speed drill (HSD) technique. A retrospective analysis was conducted on patients undergoing posterior screw-rod fixation for AAI between December 2017 and July 2023. The patients were divided into two groups based on the tools used for screw placement: UBB and HSD. Data on surgical duration, estimated blood loss, spinal cord and arterial injury incidence, screw placement accuracy, neurological status measured by the Japanese Orthopedic Association (JOA) score and fusion rates, were collected and analyzed. 13 patients received C1 pedicle screw placement via UBB facilitation, while 8 were treated using the HSD approach. The UBB group showed a significant reduction in blood loss and operation time compared to the HSD group (P=0.002 and P<0.001, respectively). No spinal cord or arterial injuries occurred in either group. Optimal screw placement was confirmed in all UBB cases versus 87.5% in the HSD group (P=0.139). Both groups demonstrated significant improvements in JOA scores with no inter-group difference. The fusion rate was 100% in the UBB group and 87.5% in the HSD group, not statistically different (P=0.381). UBB is a viable alternative for C1 pedicle screw placement, associated with reduced blood loss and shorter operation time, while achieving comparable clinical outcomes to the conventional HSD method. Nevertheless, further research with a larger sample size is needed.

A novel technique for C1-C2 posterior screw insertion using patient-specific guides created by CT-based 3D printing.

C1-C2 fixation has been developed for the rigid fusion of atlantoaxial instability. C1 lateral mass screw (C1 LMS)-C2 pedicle screw fixation is used more frequently due to its rigid fixation and high bone fusion rate. However, C1 screw placement is relatively unsafe even with recently developed image-based navigation systems. Patient-specific screw guide templates (PSGT) were developed to improve the accuracy and safety of C1 screw placement. Herein, we investigated the outcomes of the C1-C2 posterior fixation technique using PSGT. This was a retrospective study of six patients who underwent posterior cervical spinal fusion using the PSGT between January 2022 and April 2023. Operative time, estimated blood loss, intraoperative radiation dose, surgical cost, and screw placement accuracy were evaluated and compared with those achieved with preoperative CT-based navigation (navigation group, n = 15). Screw accuracy was assessed using Neo's classification. PSGT showed good results, although the differences were not statistically significant (operation time: 104.3 ± 9.7 min vs 116.4 ± 20.8 min; estimated blood loss: 56.7 ± 72.4 mL vs 123.2 ± 162.3 mL; and radiation dose: 1.8 ± 1.2 mSv vs 2.6 ± 0.8 mSv, respectively). PSGT was particularly better in terms of the accuracy of C1 LMS (PSGT: 100%, navigation: 83.3%). The deviation at the entry point was minimal, and the difference between the sagittal and transversal angles from the preoperative plan was small. We investigated the clinical efficacy of using the PSGT for C1-C2 posterior fixation. PSGT improved the accuracy of C1 LMS insertion.

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.

Reply to "Concerning the Article Feasibility of C2 Pedicle Screw Fixation with the "in-out-in" Technique for Patients with Basilar Invagination".

Reply to "Concerning the Article Feasibility of C2 Pedicle Screw Fixation with the "in-out-in" Technique for Patients with Basilar Invagination".

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 C2 isthmus screw provided sufficient biomechanical stability in the setting of atlantoaxial dislocation-a finite element study

BackgroundThe emerging of the C2 isthmus screw fixation technique is gaining popularity in the setting of atlantoaxial dislocation or other conditions requiring fixation of C2. However, the biomechanical stability of this fixation is poorly understood.PurposeTo compare and elucidate the biomechanical stability of C2 pedicle screw (C2PS), C2 isthmus screw (C2IS) and C2 short isthmus screw (C2SIS) fixation techniques in atlantoaxial dislocation (AAD).MethodA three-dimensional finite element model (FEM) from occiput to C3 was established and validated from a healthy male volunteer. Three FEMs, C1 pedicle screw (PS)-C2PS, C1PS-C2IS, C1PS-C2SIS were also constructed. The range of motion (ROM) and the maximum von Mises stress under flexion, extension, lateral bending and axial rotation loading were analyzed and compared. The pullout strength of the three fixations for C2 was also evaluated.ResultC1PS-C2IS model showed the greatest decrease in ROM with flexion, extension, lateral bending and axial rotation. C1PS-C2PS model showed the least ROM reduction under all loading conditions than both C2IS and C2SIS. The C1PS-C2PS model had the largest von Mises stress on the screw under all directions followed by C1PS-C2SIS, and lastly the C1PS-C2IS. Under axial rotation and lateral bending loading, the three models showed the maximum and minimum von Mises stress on the screw respectively. The stress of the three models was mainly located in the connection of the screw and rod. Overall, the maximum screw pullout strength for C2PS, C2IS and C2SIS were 729.41N, 816.62N, 640.54N respectively.ConclusionIn patients with atlantoaxial dislocations, the C2IS fixation provided comparable stability, with no significant stress concentration. Furthermore, the C2IS had sufficient pullout strength when compared with C2PS and C2SIS. C2 isthmus screw fixation may be a biomechanically favourable option in cases with AAD. However, future clinical trials are necessary for the evaluation of the clinical outcomes of this technique.

Posterior atlantoaxial fixation of osteoporotic odontoid fracture: biomechanical analysis of the Magerl versus harms techniques in a cadaver model

BACKGROUND CONTEXTOdontoid fractures are among the most common cervical spine fractures in the elderly and are associated with increased morbidity and mortality. Clinical evidence suggests improved survival and quality of life after operative intervention compared to nonoperative treatment. PURPOSEThis study seeks to examine the stability of an osteoporotic Type II odontoid fracture following posterior atlantoaxial fixation with either the Magerl transarticular fixation technique or the Harms C1 lateral mass screws C2 pedicle screw rod fixation. STUDY DESIGNBiomechanical cadaveric study. METHODSEighteen cadaveric specimens extending from the cephalus to C7 were used in this study. Reflective marker arrays were attached to C1 and C2 and a single marker on the dens to measure movement of each during loading with C2–C3 and occiput-C1 being allowed to move freely. A biomechanical testing protocol imparted moments in flexion-extension, axial rotation, and lateral bending while a motion capture system recorded the motions of C1, C2, and the dens. The spines were instrumented with either the Harms fixation (n=9) or Magerl fixation (n=9) techniques, and a simulated Type II odontoid fracture was created. Motions of each instrumented spine were recorded for all moments, and then again after the instrumentation was removed to model the injured, noninstrumented state. RESULTSBoth Harms and Magerl posterior C1–C2 fixation allowed for C1, C2, and the dens to move as a relative unit. Without fixation the dens motion was coupled with C1. No significant differences were found in X, Y, Z translation motion of the dens, C1 or C2 during neutral zone motions between the Magerl and Harms fixation techniques. There were no significant differences found in Euler angle motion between the two techniques in either flexion-extension, axial rotation, or lateral bending motion. CONCLUSIONSOur findings suggest that both Harms and Magerl fixation can significantly reduce dens motion in Type II odontoid fractures in an osteoporotic cadaveric bone model. CLINICAL SIGNIFICANCEBoth Harms and Magerl posterior atlantoaxial fixation techniques allowed for C1, C2, and the dens to move as a relative unit following odontoid fracture, establishing more anatomic stability to the upper cervical spine.

Accuracy and clinical characteristics of robot-assisted cervical spine surgery: a systematic review and meta-analysis.

To evaluate the accuracy and feasibility of robot-assisted cervical screw placement and factors that may affect the accuracy. A comprehensive search was made on PubMed, Embase, Cochrane Library, Web of Science, CNKI, and Wanfang Med for the selection of potential eligible literature. The outcomes were evaluated in terms of the relative risk (RR) or standardized mean difference (MD) and corresponding 95% confidence interval (CI). Subgroup analyses of the accuracy of screw placement at different cervical segments and with different screw placement approaches were performed. A comparison was made between robotic navigation and conventional freehand cervical screw placement. Six comparative cohort studies and five case series studies with 337 patients and 1342 cervical screws were included in this study. The perfect accuracy was 86% (95% CI, 82-89%) and the clinically acceptable rate was 98% (95% CI, 95-99%) in robot-assisted cervical screw placement. The perfect accuracy of robot-assisted C1 lateral mass screw placement was the highest (96%), followed by C6-7 pedicle screw placement (93%) and C2 pedicle screw placement (86%), and the lowest was C3-5 pedicle screw placement (75%). The open approach had a higher perfect accuracy than the percutaneous/intermuscular approach (91% vs 83%). Compared with conventional freehand cervical screw placement, robot-assisted cervical screw placement had a higher accuracy, a lower incidence of perioperative complications, and less intraoperative blood loss. With good collaboration between the operator and the robot, robot-assisted cervical screw placement is accurate and feasible. Robot-assisted cervical screw placement has a promising prospect.

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.

Establishing Safe Surgical Parameters for Placement of C2 Pedicle Screws: A Retrospective Study.

The study aimed to evaluate the safety and feasibility of transpedicular instrumentation for the C2 vertebra and to establish the precise anatomical parameters and boundaries within which this procedure can be safely and effectively performed. This retrospective study analyzed 66 patients who underwent C2 transpedicular screw fixation. Preoperative and postoperative axial, sagittal, and coronal computed tomography (CT) scans were examined. Anatomical measurements were taken to determine the horizontal and vertical distances from the C2 pedicle projection to the vertebral foramen using CT images. Based on the anatomical location of the vertebral artery within the C2 vertebral foramen, the patients were divided into four subgroups using the horizontal pedicle width (HPW) and vertical pedicle width (VPW) of the C2 spine. The average age of the patients included in the study was 46.48 years. The patient population comprised 32 (48.5%) males and 34 (51.5%) females. Based on the anatomical measurements, the distribution of C2 vertebra types was as follows: type 1 accounted for 68.9%, type 2 for 3.8%, type 3 for 16.7%, and type 4 for 10.6%. Significantly narrower pedicle widths were observed in types 2 and 4 compared to other vertebra types. Type 2 had the largest medial angle (MA), while type 4 had the narrowest MA. In terms of the sagittal plane, type 4 exhibited the widest MA and type 3 had the narrowest MA, but these differences were not statistically significant. Among the cases, 12 (18.1%) involved the vertebral foramen, with 1 case (8.3%) showing screw-related vertebral artery injury (0.75% of all screws). No vertebral artery injuries were observed with the other transpedicular screws. Preoperative anatomical measurements for patients undergoing transpedicular instrumentation on the C2 vertebra should include planning CT images on three planes: axial, sagittal, and coronal.

Free-hand technique of C7 pedicle screw insertion using a simply defined entry point without fluoroscopic guidance for cervical spondylotic myelopathy patients with C3 to C6 instrumented by lateral mass screws: a retrospective cohort study

BackgroundNowadays, both lateral mass screw (LMS) and pedicle screw were effective instrumentation for posterior stabilization of cervical spine. This study aims to evaluate the feasibility of a new free-hand technique of C7 pedicle screw insertion without fluoroscopic guidance for cervical spondylotic myelopathy (CSM) patients with C3 to C6 instrumented by lateral mass screws.MethodsA total of 53 CSM patients underwent lateral mass screws instrumentation at C3 to C6 levels and pedicle screw instrumentation at C7 level were included. The preoperative 3-dimenional computed tomography (CT) reconstruction images of cervical spine were used to determine 2 different C7 pedicle screw trajectories. Trajectory A passed through the axis of the C7 pedicle while trajectory B selected the midpoint of the base of C7 superior facet as the entry point. All these 53 patients had the C7 pedicle screw inserted through trajectory B by free-hand without fluoroscopic guidance and the postoperative CT images were obtained to evaluate the accuracy of C7 pedicle screw insertion.ResultsTrajectory B had smaller transverse angle, smaller screw length, and smaller screw width but both similar sagittal angle and similar pedicle height when compared with trajectory A. A total of 106 pedicle screws were inserted at C7 through trajectory B and only 8 screws were displaced with the accuracy of screw placement as high as 92.5%.ConclusionIn CSM patients with C3 to C6 instrumented by LMS, using trajectory B for C7 pedicle screw insertion is easy to both identify the entry point and facilitate the rod insertion.

CT-navigated C2 Pedicle Screw insertion using dynamic reference array on C2 spinous process: A Novel Technique

ntroduction: Spine surgeons have endeavoured to improve the accuracy of pedicle screw insertion. Computed tomography (CT) guided navigation has been helpful in precisely passing pedicle screws even further accurately but, there were shortcomings noted with the technique due to movement between reference frame and anatomical landmarks, especially in the cervical spine which led to injury of vital neurovascular structures. Thus, there was a need for developing a technique which would eliminate the inherent error due to movement in the vertebral body while passing screws. Research Question: Can using C2 spinous process as an attachment for the reference array improve accuracy of C2 pedicle screws. Material and Methods: We prospectively studied data of 10 patients (20 screws) in whom Computed tomography navigated C2 pedicle screws insertion was carried out using the reference array on C2 spinous process. Accuracy of pedicle screws were confirmed by post instrumentation Computed tomography scan immediately intra operatively. Results: With the presented technique overall breach rate was 5% with one screw having a medial breach of grade 1 with no incidence of neurovascular injury or need for further revision. Discussion and Conclusion: Results from this study shows better accuracy than other techniques described to pass C2 pedicle screws eliminating the error in movement from the cervical vertebrae and the reference frame being nearest to the C2 pedicle. Although there is a learning curve with the adoption of the navigation system, with experience, the challenges associated with Cervical pedicle screws (CPS) insertion can be overcome.

C1 Transposterior Arch Lateral Mass Screws Combined With C2 Pedicle Screw and Rod Fixation for Pediatric Atlantoaxial Subluxation: A Minimal 10-Year Follow-up Outcome Analysis.

Although the short-term outcomes of the 1-step reduction and fixation technique using C1 transposterior arch lateral mass screws combined with C2 pedicle screw and rod fixation system for the treatment of pediatric atlantoaxial subluxation (AAS) have been satisfactory, its long-term outcomes and impact on spinal development are not well studied. This study was intended to assess the long-term reliability of this technique for pediatric AAS. A retrospective case series study was conducted to analyze the minimum 10-year follow-up outcomes from 7 pediatric patients with AAS who underwent atlantoaxial fusion using the aforementioned technique. Quality of life and cervical range of motion were both measured thoroughly. In addition, vertical growth within the fusion construct (C1-2), overall cervical alignment, and subaxial cervical spine degeneration were evaluated radiographically. The mean age of the 7 patients was 8.14 ± 2.41 (6-12) years at the time of surgery. The mean follow-up period was 11.00 ± 1.15 (10-13) years. No patients presented identifiable intervertebral disk degeneration or segmental instability in the subaxial cervical spine except for 1 patient who showed mild intervertebral disk degeneration. Vertical growth did continue within the atlantoaxial complex after surgery (11.90% ± 2.37%); however, there was a decrease in the percentage of vertical growth compared with the corresponding normal populations of the same age and sex. Moreover, there was a significant decrease in the range of cervical extension and rotation motion, and the overall cervical alignment straightened at the latest follow-up. The 1-step reduction and fixation technique is a relatively reliable surgical technique for pediatric AAS, which does not adversely affect the postoperative quality of life or the subaxial cervical degeneration. Nevertheless, certain limitations, such as decreased cervical range of motion and changes in cervical alignment, should be concerned.

Clinical and Radiological Outcomes after Surgical Stabilization of Craniovertebral Junction – A Single-center Experience

Abstract Background and Objectives: Craniovertebral instability and its surgical management require a thorough knowledge of the anatomy and dynamics of the craniovertebral junction (CVJ). Due to the wide range of mobility and proximity of vital neurovascular structures, these surgeries demand high technical skill and precision. It is very difficult to suggest a single good technique for CVJ stabilization as each procedure has got its own indications and benefits. Novel techniques and gadgets like neuro navigation and robotic arms help surgeons to minimize complications, thereby improving the overall functional outcome. In this study, we are analyzing the retrospective data of CVJ instabilities surgically managed by freehand technique in our institute. Materials and Methods: We did a retrospective analysis of 33 patients operated on for craniocervical junction instability for 7 years from January 1, 2015, to December 31, 2021. We analyzed the clinical and radiological presentations and postoperative outcomes at 3 weeks, 6 months, and after 1 year. The distribution of clinical presentation in terms of neck pain, myelopathy, restricted neck movements, and lower cranial nerve palsy was evaluated and correlated with the demographic parameters. The paired “t”- test was used to correlate the clinical and radiological outcomes after surgery. Results: The paired “t” value of the clinical improvement assessed with the preoperative and postoperative Japanese Orthopedic Association (JOA) myelopathic scores was − 4.376 with P &lt; 0.001, which indicates a significant clinical improvement 6 months after surgery. Among the 33 patients evaluated, only three patients developed a slight reduction in the JOA score after surgery, which was improved within 1 year. All the patients achieved satisfactory trabecular bone formation at the graft site and decorticated joint facets without any clinical or radiological evidence of implant failure. Among the C2 pedicle screws, 3 (7.5%) were having vertebral foraminal impingement, and 2 (5%) were having medial cortical violation and spinal canal impingement. All the patients with radiological evidence of implant malposition were clinically intact and did not show any deterioration of the studied myelopathic score (JOA). Conclusions: As the bony anatomy and the vascular course of the CVJ vary from patient to patient, thorough preoperative planning is mandatory for the surgical management of CVJ instability. In our study, the clinical and radiological improvement after surgical stabilization of craniovertebral instability by freehand technique is comparable with the available data. The overall risk of screw malposition and associated lethal complications may be minimized by adding modern technologies such as neuronavigation, robotic arms, and three-dimensional C-arm in the armamentarium.

Different C2 screw placement techniques with mobilization of the vertebral artery in high-riding vertebral artery cases: Cadaver dissection.

In neurosurgery, posterior approaches intended at the craniovertebral junction are frequently used. The most popular procedures for treating upper cervical instability are C1 lateral mass, C2 pedicle, and C1-C2 transarticular screw stabilization. Due to their proximity to neural structures and the presence of the high-riding vertebral artery (VA), these techniques are complicated. The risk of VA damage can be decreased by mobilizing the VA. Using cadaveric specimens in this study was aimed to demonstrate C2 pedicle and C1-C2 transarticular screw placement with VA mobilization and a novel C2 inferior corpus screw placement technique. In this study, twelve adult cadaveric specimens and two adult dry cadaveric C2 bones were used with the permission and decision of the University Research Ethics Committee. Colored silicone was injected into the arteries and veins of these twelve cadaveric specimens. Then, muscle dissection was performed stepwise, and the C2 vertebrae of the cadavers were revealed with a surgical microscope. Each specimen and entire stages of the dissections were recorded photographically. After cadaver dissections, screw placement was performed with three different techniques. Finally, radiological imaging was done with fluoroscopy. After dissection, the lateral mass of the C2 vertebra was observed, and lateral to it, the transverse process and foramen were detected with the help of a hook. Next, the posterior wall of the VA groove was removed using a 1 mm thin plate Kerrison rongeur until the VA loop could partially be observed the VA. This enables us to find the top of the loop of the VA and mobilize it inferiorly using a dissector. Following this step, the C1-2 transarticular, C2 pedicle, and the novel C2 inferior corpus screw placement can be performed safely by directly visualizing the artery. Due to the nearby neurologic and vascular structures, placing the C2 pedicle and C1-2 transarticular screw is a challenging procedure, especially in high-riding VA cases. However, it is possible to place the C2 pedicle, C1-2 transarticular, and novel C2 inferior corpus screw after the mobilization of the VA. This study aimed to show all of them together on a cadaver for the first time, to understand the anatomy of the C2 vertebra, and to use screw placement techniques to minimize the risk of complications.

Letter to the Editor Concerning "Feasibility of C2 Pedicle Screw Fixation with the "in-out-in" Technique for Patients with Basilar Invagination".

Letter to the Editor Concerning "Feasibility of C2 Pedicle Screw Fixation with the "in-out-in" Technique for Patients with Basilar Invagination".

Comparison of intraoperative CT- and cone beam CT-based spinal navigation for the treatment of atlantoaxial instability

BACKGROUND CONTEXTDue to the complexity of neurovascular structures in the atlantoaxial region, spinal navigation for posterior C1–C2 instrumentation is nowadays a helpful tool to increase accuracy of surgery and safety of patients. Many available intraoperative navigation devices have proven their reliability in this part of the spine. Two main imaging techniques are used: intraoperative CT (iCT) and cone beam computed tomography (CBCT). PURPOSEComparison of iCT- and CBCT-based technologies for navigated posterior instrumentation in C1-C2 instability. STUDY DESIGNRetrospective study. PATIENT SAMPLEA total of 81 consecutive patients from July 2014 to April 2020. OUTCOME MEASURESScrew accuracy and operating time. METHODSPatients with C1–C2 instability received posterior instrumentation using C2 pedicle screws, C1 lateral mass or pedicle screws. All screws were inserted using intraoperative imaging either using iCT or CBCT systems and spinal navigation with autoregistration technology. Following navigated screw insertion, a second intraoperative scan was performed to assess the accuracy of screw placement. Accuracy was defined as the percentage of correctly placed screws or with minor cortical breach (<2 mm) as graded by an independent observer compared to misplaced screws. RESULTSA total of 81 patients with C1–C2 instability were retrospectively analyzed. Of these, 34 patients were operated with the use of iCT and 47 with CBCT. No significant demographic difference was found between groups. In the iCT group, 97.7% of the C1–C2 screws were correctly inserted; 2.3% showed a minor cortical breach (<2 mm); no misplacement (>2 mm). In the CBCT group, 98.9% of screws were correctly inserted; no minor pedicle breach; 1.1% showed misplacement >2 mm. Accuracy of screw placement demonstrated no significant difference between groups. Both technologies allowed sufficient identification of screw misplacement intraoperatively leading to two screw revisions in the iCT and three in the CBCT group. Median time of surgery was significantly shorter using CBCT technology (166.5 minutes [iCT] vs 122 minutes [CBCT]; p<.01). CONCLUSIONSSpinal navigation using either iCT- or CBCT-based systems with autoregistration allows safe and reliable screw placement and intraoperative assessment of screw positioning. Using the herein presented procedural protocols, CBCT systems allow shorter operating time.

Clinicoradiological evaluation and outcome assessment of single-stage posterior correction of atlantoaxial dislocation

Background: Atlantoaxial dislocation (AAD) refers to loss of stability between atlas and axis vertebrae, resulting in loss of normal articulation. It may be due to congenital, traumatic, or inflammatory reasons. Various techniques of atlantoaxial fixation have been described and used in patients over the years, but each has its own merits and demerits. Aims and Objectives: The aim of the study was to study clinicoradiological evaluation and outcome assessment of single-stage posterior correction of AAD. Materials and Methods: This is a prospective study done in the Department of Neurosurgery, JA group of hospitals, Gajra Raja Medical College, Gwalior, from July 2021 to July 2022. The study was conducted on 20 randomly selected patients whose presentation and imaging showed indication for surgery. Results: C1 lateral mass C2 pars screw fixation had one Frankel grade improvement in 6 months in 96% patient with a fusion rate of 100% and the patient also has modified Japanese orthopedic association score improvement of 15.25±0.98. Conclusion: This study reviewed single-stage posterior correction of AAD using C1 lateral mass and C2 pedicle screw and rod fixation; it enables the stabilization of atlantoaxial motion and preserves motion at occipito-atlantal level with high fusion rates, good neurological recovery, and minimal complications.

Posterior Reduction and Intra-Articular Cage Fusion With a C2 Nerve Root Preservation Technique for Treating Posterior Atlantoaxial Dislocation Secondary to Os Odontoideum.

Posterior C1-C2 interlaminae compression fusion with iliac bone graft may lead to donor site complications and recurrent C1 posterior dislocation for posterior atlantoaxial dislocation (AAD) secondary to os odontoideum. C1-C2 intra-articular fusion often needs C2 nerve ganglion transection to facilitate exposing and manipulating the facet joint, leading to bleeding from the venous plexus and suboccipital numbness or pain. Therefore, this study was conducted to evaluate the outcomes of posterior C1-C2 intra-articular fusion with a C2 nerve root preservation technique in the treatment of posterior AAD secondary to os odontoideum. Data of the 11 patients who underwent C1-C2 posterior intra-articular fusion because of posterior AAD secondary to os odontoideum were retrospectively reviewed. Posterior reduction was performed using C1 transarch lateral mass screws and C2 pedicle screws. Intra-articular fusion was performed using a polyetheretherketone cage filled with autologous bone from the caudal edge of the C1 posterior arch and cranial edge of the C2 laminar. Outcomes were evaluated by using the Japanese Orthopaedics Association score, Neck Disability Index, and visual analog scale for neck pain. Bone fusion was evaluated by using computed tomography and 3-dimensional reconstruction. The average follow-up duration was 43.9 ± 9.5 months. All patients achieved good reduction and bone fusion, without transection of the C2 nerve roots. The mean bone fusion time was 4.3 ± 1.1 months. There was no complication related to the surgical approach and instrumentation. Function of the spinal cord manifested by the Japanese Orthopaedics Association score significantly improved ( P < .05). The Neck Disability Index score and visual analog scale for neck pain markedly decreased (all P < .05). Posterior reduction and intra-articular cage fusion with a C2 nerve root preservation technique was a promising treatment of posterior AAD secondary to os odontoideum.