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OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

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Basilar invagination (BI) is a common deformity. This study aimed to quantitatively evaluate the height of clivus and atlanto-occipital lateral mass (LM) in patients with BI with or without atlas occipitalization (AOZ). We evaluated 166 images of patients with BI and of controls. Seventy-one participants were control subjects (group A), 68 had BI with AOZ (group B), and 27 had BI without AOZ (group C). Parameters were defined and measured for comparisons across the groups. Multiple linear regression analysis was used to test the relationship between Chamberlain's line violation (CLV) and the clivus height ratio or atlanto-occipital LM height. Based on the degree of AOZ, the lateral masses in group B were classified as follows: segmentation, incomplete AOZ, complete AOZ. From groups A to C, there was a decreasing trend in the clivus height and clivus height ratio. There was a linear negative correlation between the clivus height ratio and CLV in the three groups. Generally, the atlanto-occipital LM height followed the order of group B < group C < group A. The atlanto-occipital LM height was included only in the equations of groups B. There were no cases of atlantoaxial dislocation (AAD) in group C. There was a decreasing trend in LM height from the segmentation type to the complete AOZ type in group B. BI can be divided into three categories: AOZ causes LM height loss; Clivus height loss; Both clivus and LM height loss. The clivus height ratio was found to play a decisive role in both controls and BI group, while the atlanto-occipital LM height loss caused by AOZ could be a secondary factor in patients with BI and AOZ. AOZ may be a necessary factor for AAD in patients with congenital BI. The degree of AOZ is associated with LM height in group B.

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INTRODUCTION: Long lateral mass screw (LLMS) technique for posterior cervical fusion has been performed in our hospital since 2019. In this study, the LLMS insertion technique, deviation rate, and insertion torque have been described. Moreover, several major concerns associated with LLMS have been adequately addressed. METHODS: This study included 58 patients (43 men and 15 women) who had undergone LLMS surgery at our hospital during the four-year period from December 2019 to December 2023, and were evaluated using postoperative CT. The evaluation parameters included the screw length at each vertebral segment, screw angle in the sagittal section, distance between the screw heads, and complications. RESULTS: The median screw length at C3 was 23.0 mm (22.0-24.0 mm), the screw angle was 36.1° (31.6-41.8°), and the distance between screw heads was 13.8 mm (11.6-17.2 mm). The median screw length at C4 was 22.0 mm (21.0-24.0 mm), the screw angle was 36.2° (28.7-40.7°), and the distance between screw heads was 15.9 mm (13.0-19.0 mm). The median screw length at C5 was 21.0 mm (20.0-22.0 mm), the screw angle was 35.6° (28.0-39.7°), and the distance between screw heads was 17.6 mm (15.1-20.4 mm). The median screw length for C6 was 20.0 mm (19.0-22.0 mm), the screw angle was 29.2° (25.2-36.8°), and the distance between screw heads was 20.4 mm (16.1-24.4 mm). CONCLUSION: The major limitations of the LLMS technique were inadequate screw angle, difficulty inserting long screws, inadequate decompression, and the inability to perform cervical laminoplasty. However, these limitations did not substantially affect the efficiency of LLMS. LLMS has fewer complications and can insert longer screws than LMS.

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OBJECTIVE: The study aimed to evaluate the safety, feasibility, effect on fusion, and clinical efficacy of atlas lateral mass and C2-3 transfacet screw fixation technique, serves as an alternative method to traditional posterior atlantoaxial fixation. METHODS: Patients with atlantoaxial instability who underwent atlas lateral mass and C2-3 transfacet fixation surgery were included. The duration of the surgery and the quantity of blood lost during the operation were recorded. Patients were monitored via X-ray and computed tomography scans to evaluate the degree of fusion at the 1-month and 12-month follow-up. The Neck Visual Analog Scale and Neck Disability Index were evaluated preoperatively, in the postoperative first week, and at the 12-month follow-up for clinical follow-up. RESULTS: A total of 8 patients with atlantoaxial instability due to odontoid fracture or Arnold- Chiari malformation accompanied by bony or vascular abnormalities were included in the study between 2017 and 2024. All 8 patients underwent successful atlas lateral mass and C2-3 transfacet screw fixation, with no neurovascular injury noted during surgery. All patients with fracture exhibited fusion at the 12-month mark, and both the Neck Visual Analog Scale and Neck Disability Index scores demonstrated significant improvement at both the 1-week and 12-month postoperative periods (P < 0.05). CONCLUSIONS: The atlas lateral mass and C2-3 transfacet screw fixation technique, an alternative to conventional posterior fixation, has been demonstrated to be an efficacious method for providing adequate stabilization and fusion in patients with atlantoaxial instability, even in the cases of thin C2 pedicle, high-riding vertebral artery, previous failed surgeries, or reoperation.

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Background: Overview of the literature - Fractures of the C1 constitute 3%-13% of all cervical spine injuries in adults. Most isolated C1 fractures are stable and can be treated nonoperatively with external immobilization. Traditional surgical options for C1 fracture treatment are occiput-to-C2 fusion or C1 with lateral mass screws (LMSs). Purpose - The aim is to assess the management and perioperative complications of C1 fractures undergoing LMS fusion between fluoroscopy and computed tomography (CT)-guided navigation. Methods: This was a retrospective multicenter study of data from the DWG-Register of patients who underwent operative treatment for C1 traumatic fracture with LMSs from January 2017 to September 2022. Inclusion criteria - traumatic injury and age > 18 years old. Results: In total, 202 patients with traumatic C1 fracture requiring spinal surgery were identified in the registry; n = 175 (Group 1) were treated conventionally without CT-guided navigation and n = 27 were treated with CT-guided navigation (Group 2). C1-LMS was principally performed by spine surgeons n = 90 (53.4%) and n = 72 (18.5%) by neurosurgeons in both the groups. Intraoperative adverse events were as follows: dural tear in group 1 n = 0 and in group 2 n = 1, vascular injury, with one case in group 1 and no cases in group 2. General complications were: cardiovasculars in group 1 n = 6 (3.4%) and Group 2 n = 4 (14.8%) (P = 0.03), pulmonary complications in group1 n = 2 (1.1%) and n = 9 in group 2 (33.3%) (P < 0.001), stroke n = 1 (0.57%) in group1 and n = 4 in group 2 (14.8%) (P < 0.001), gastrointestinal bleeding n = 1 (0.57%) in group1 and no cases in group 2, renal insufficiency n = 2 (1.1%) in group 1 and n = 3 (11.1%) in group 2 (P = 0.01). One death was recorded in group 2 (3.7%). Conclusion: This series of 404 screws placed in 202 patients over 5 years who underwent two types of C1 fracture fixation had a considerably lower incidence of screw malposition and vertebral artery injury than has previously been reported in the literature. C1 screws can be safely placed with a low risk of vertebral artery and neurologic injury with and without CT-guided navigation support.

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OBJECTIVE: The C4 is the transition point between the upper and lower cervical vertebrae and plays a pivotal role in the middle of the cervical spine. Currently, there are limited reports on large-scale sample studies regarding C4 anatomy in children, and a scarcity of experience exists in pediatric cervical spine surgery. The current study addresses the dearth of anatomical measurements of the C4 vertebral arch and lateral mass in a substantial sample of children. This study aims to measure the imaging anatomy of the C4 vertebral arch and lateral mass in children under 14 years of age across various age groups, investigate the growth and development of these structures. METHODS: We measured 12 indicators, including the size (D1, D2, D3, D4, D5, D6, D7, and D8) and angle (A, C, D, and E) of the C4 vertebral arch and lateral mass, in 513 children who underwent cervical CT examinations at our hospital. We employed the aggregate function for statistical analysis, conducted t-tests for difference statistics, and utilized the least squares method for regression analysis. RESULTS: Overall, as age increased, there was a gradual increase in the size of the vertebral arch and lateral mass. Additionally, the medial inclination angle of the vertebral arch decreased, and the lateral mass flattened gradually. The rate of change decreased gradually with age. The mean value of D1 increased from 2.31 mm to 3.88 mm, of D2 from 16.75 mm to 29.2 mm, of D3 from 2.21 mm to 4.92 mm, and of D4 from 7.34 mm to 11.84 mm. Meanwhile, the mean value of D5 increased from 5.2 mm to 9.71 mm, of D6 from 10.19 mm to 16.16 mm, of D7 from 2.53 mm to 5.67 mm, and of D8 from 6.11 mm to 11.45 mm. Angle A ranged from 49.12° to 54.97°, angle C from 15.28° to 19.83°, angle D from 39.91° to 53.7°, and angle E from 18.63° to 28.08°. CONCLUSION: Prior to cervical spine surgery in children, meticulous CT imaging anatomical measurements is essential. The imaging data serves as a reference for posterior C4 internal fixation, aids in designing posterior cervical screws for pediatric patients, and offer morphological anatomical references for posterior cervical spine surgery and screw design in pediatric patients.

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OBJECTIVE: For degenerative diseases accompanied by cervical malalignment, the starting and ending points of fixation for better cervical sagittal alignment and clinical results are not as clear as the thoracolumbar region. In this study we aimed to compare the effects of posterior subaxial cervical fixation (PSCF), posterior cervical fixation extending to the upper thoracic region and posterior upper cervical fixation extending to the upper thoracic region on cervical sagittal alignment. METHODS: Sixty-three patients who underwent posterior cervical and cervical-up thoracic fixation were retrospectively analyzed in a comparative study. The procedures that we performed from May 2019 to March 2022 on these 63 patients were: (1) C3-C6 group-posterior subaxial cervical fixation; (2) Subaxial-T2 group-posterior subaxial cervicothoracic fixation (PSCTF); (3) C2-T2 upper thoracic posterior fixation group. The C3-C6 group had 27 patients, Subaxial-T2 group had 24, and C2-T2 group had 12. We determined the minimum follow-up period as 12 months. C0-2, C2-7 lordosis angle, sagittal vertical axis (SVA), C2 slope, C7 slope, T1 slope, cervical slope, neck slope, and thoracic inlet angle (TIA) measurements were made in three patient groups. Comparatively, cervical sagittal alignment was evaluated. RESULT: In the C2-T2 group, a significant increase in C2-C7 lordosis, decrease in C2 slope, and increase in TS-CL were observed. Significant C2-C7 lordosis decrease, C2 slope increase, and TS-CL decrease were observed in the C3-C6 group. A significant increase in C2-C7 lordosis and a decrease in C2 slope were observed in the subaxial-T2 group. No significant change was observed in the TS-CL angle. CONCLUSION: In cervical degenerative disorders accompanied by cervical malalignment, we recommend the C2-T2 fixation method, which provides the desired C2-C7 lordosis, SVA within the normal range, and the best Neck Disability Index results.

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Atlantoaxial dislocations (AAD) are a diverse set of C1-C2 rotatory subluxations that include the inferior and superior axial facet articulations. C1-C2 segments are both covered by cranial-cervical ligaments, indicating that AAD would damage both joints. Whenever the posterior elements are missing or impaired, lateral mass screw fixation has replaced alternative posterior cervical fixation procedures as the preferred treatment for securing the sub-axial cervical spine. An increase in muscle tone, hyperreflexia, pathological reflexes, digit/hand clumsiness, and gait deviations caused by spinal cord compression at the cervical level are the most common clinical features. A 23-year-old female patient came with the chief complaint of weakness, tingling sensation, and numbness in both upper and lower limbs along with imbalance while walking. She had a history of falls which was managed conservatively. As the symptoms progressed, an MRI, a CT scan, and an X-ray of the neck were done to rule out the level of injury which revealed AAD, and the patient was operated on for C1-C2 lateral mass fixation. Post-operatively, the patient was referred to the physiotherapy department for further management. The patient's quality of life and daily functioning were positively affected after undergoing early intervention as measured by the Functional Independence Measure, Neck Disability Index, Berg Balance Scale, and Dynamic Gait Index.

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Posterior fixation of the subaxial cervical spine (SCS) commonly relies on the application of lateral mass screws (LMS), with pedicle screws being a less prevalent alternative. The present study provides another option: A recently introduced novel approach, the Attallah screw, intended to ensure a safety profile comparable to that of LMS, combined with a strength profile similar to that of pedicle screws. The focus of the present study is the comparative analysis of peak insertion torques for these three screw types. Employing standard surgical techniques and instruments, Attallah screws were scheduled for insertion on the right side of the SCS in 15 cadavers, pedicle screws on the left side in 8 cadavers, and LMS on the left side in the remaining 7 cadavers. The peak insertion torque was recorded using an electronic torque screwdriver. The results revealed that the peak insertion torques were similar in the pedicle and the Attallah screw at C3, C4 and C7, but differed at C5 (mean ± SD; pedicle, 79.5±19.6 cNm; Attallah, 56.7±18.5 cNm; P=0.029) and C6 (pedicle, 85.4±28.7 cNm; Attallah, 49.8±17.9 cNm; P=0.004) in favor of the superior pedicle screw measurements. The peak insertion torques of the pedicle screw were superior to the corresponding data from the LMS from C4 to C7. By contrast, the peak insertion torques of the Attallah screw were only superior to those of the LMS at C7 (Attallah, 69.5±24.5 cNm; lateral mass, 40.5±21.4 cNm; P=0.030), although similar trends were observed at the other cervical levels. On the whole, the findings presented herein indicate the level-dependent superior robustness of the Attallah screw as a posterior cervical fixation method compared to the LMS. However, from a biomechanical perspective, the pedicle screw remains the preeminent choice for fixation within the C5-C6 range.

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BACKGROUND: The technique of spinal decompression under endoscopy has been widely applied, but reports on endoscopic cervical fixation are rare. The unilateral biportal endoscopic (UBE) technique stands out for its lesser muscle intrusion and more flexible surgical approach. METHOD: We applied the UBE approach for cervical fixation and laminectomy. We achieved bilateral lateral mass screw fixation by making an auxiliary UBE portal combined with the Roy-Camille and Magerl techniques. CONCLUSIONS: Our successful implementation of cervical fixation using the UBE technique at the C3/4 level suggests its efficacy. This approach is a valuable and minimally invasive option for cervical fixation.

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Background: Here, we assessed a new trajectory and insertion torque for the placement of a long lateral mass screw (LLMS) that offers stronger posterior fixation versus a shorter lateral mass screw (LMS) in the posterior cervical spine. We report a short technical note of the insertion torque of LLMS. Methods: The insertion trajectory/torque was evaluated in 30 patients (10 males and 20 females) undergoing posterior cervical LLMS fusions (2021-2023). Patients averaged 65 years of age. Pathology included eight cervical spine injuries, ten cord injuries, four dislocations/fractures, and eight other entities. Variables studied included the length of the LLMS inserted from C3-7, screw deviation rates, insertion torque, and adverse events. Results: A total of 146 screws were inserted: 11 pedicle screws (PSs) and 135 LLMS. The average insertion torque was 105.9 cNm for PS and 64.9 cNm for LLMS. As the screw lengthened by 1 mm, the insertion torque increased by approximately 4.4 cNm. Conclusion: Here, we documented that the insertion torque of LLMS was 66.1 cNm, greater than the 51.0 cNm for LMS, which should provide stronger posterior cervical fixation.

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The classification of medical devices by the Food and Drug Administration (FDA) involves rigorous scrutiny from specialized panels that designate devices as Class I, II, or III depending on their levels of relative risk to patient health. Posterior rigid pedicle screw systems were first classified by the FDA in 1984 and have since revolutionized the treatment of many spine pathologies. Despite this early classification by the FDA, posterior cervical pedicle and lateral mass screws were not reclassified from unclassified to Class III and then to Class II until 2019, nearly 35 years after their initial classification. This reclassification process involved a decades-long interplay between the FDA, formal panels, manufacturers, academic leaders, practicing physicians, and patients. It was delayed by lawsuits and a paucity of data demonstrating the ability to improve outcomes for cervical spinal pathologies. The off-label use of thoracolumbar pedicle screw rigid fixation systems by early adopters assisted manufacturers and professional organizations in providing the necessary data for the reclassification process. This case study highlights the collaboration between physicians and professional organizations in facilitating FDA reclassification and underscores changes to the current classification process that could avoid the prolonged dichotomy between common medical practice and FDA guidelines.

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PURPOSE: This study aimed to compare cervical sagittal parameters and clinical outcomes between patients undergoing cervical laminoplasty(CL) and those undergoing lateral mass screw fixation(LMS). METHODS: We retrospectively studied 67 patients with multilevel ossification of the posterior longitudinal ligament (OPLL) of the cervical spine who underwent lateral mass screw fixation (LMS = 36) and cervical laminoplasty (CL = 31). We analyzed cervical sagittal parameters (C2-7 sagittal vertical axis (C2-7 SVA), C0-2 Cobb angle, C2-7 Cobb angle, C7 slope (C7s), T1 slope (T1s), and spino-cranial angle (SCA)) and clinical outcomes (visual analog scale [VAS], neck disability index [NDI], Japanese Orthopaedic Association [JOA] scores, recovery rate (RR), and minimum clinically significant difference [MCID]). The cervical sagittal parameters at the last follow-up were analyzed by binary logistic regression. Finally, we analyzed the correlation between the cervical sagittal parameters and each clinical outcome at the last follow-up after surgery in both groups. RESULTS: At the follow-up after posterior decompression in both groups, the mean values of C2-C7 SVA, C7s, and T1s in the LMS group were more significant than those in the CL group (P ≤ 0.05). Compared with the preoperative period, C2-C7 SVA, T1s, and SCA gradually increased, and the C2-C7 Cobb angle gradually decreased after surgery (P < 0.05). The improvement in the JOA score and the recovery rate was similar between the two groups, while the improvement in the VAS-N score and NDI score was more significant in the CL group (P = 0.001; P = 0.043). More patients reached MCID in the CL group than in the LMS group (P = 0.036). Binary logistic regression analysis showed that SCA was independently associated with whether patients reached MCID at NDI postoperatively. SCA was positively correlated with cervical NDI and negatively correlated with cervical JOA score at postoperative follow-up in both groups (P < 0.05); C2-7 Cobb angle was negatively correlated with cervical JOA score at postoperative follow-up (P < 0.05). CONCLUSION: CL may be superior to LMS in treating cervical spondylotic myelopathy caused by OPLL. In addition, smaller cervical SCA after posterior decompression may suggest better postoperative outcomes.

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STUDY DESIGN: Basic research. PURPOSE: This finite element (FE) analysis (FEA) aimed to compare the biomechanical parameters in multilevel posterior cervical fixation with the C7 vertebra instrumented by two techniques: lateral mass screw (LMS) vs. transpedicular screw (TPS). OVERVIEW OF LITERATURE: Very few studies have compared the biomechanics of different multilevel posterior cervical fixation constructs. METHODS: Four FE models of multilevel posterior cervical fixation were created and tested by FEA in various permutations and combinations. Generic differences in fixation were determined, and the following parameters were assessed: (1) maximum moment at failure, (2) maximum angulation at failure, (3) maximum stress at failure, (4) point of failure, (5) intervertebral disc stress, and (6) influence of adding a C2 pars screw to the multilevel construct. RESULTS: The maximum moment at failure was higher in the LMS fixation group than in the TPS group. The maximum angulation in flexion allowed by LMS was higher than that by TPS. The maximum strain at failure was higher in the LMS group than in the TPS group. The maximum stress endured before failure was higher in the TPS group than in the LMS group. Intervertebral stress levels at C6-C7 and C7-T1 intervertebral discs were higher in the LMS group than in the TPS group. For both models where C2 fixation was performed, lower von Mises stress was recorded at the C2-C3 intervertebral disc level. CONCLUSIONS: Ending a multilevel posterior cervical fixation construct with TPS fixation rather than LMS fixation at the C7 vertebra provides a stiff and more constrained construct system, with higher stress endurance to compressive force. The constraint and durability of the construct can be further enhanced by adding a C2 pars screw in the fixation system.

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INTRODUCTION AND OBJECTIVES: The objective of the study was: (1) to describe changes in the shape of the atlas during growth, including gender and side differences; (2) to assess the dimension essential for identification of the optimal entry point; (3) to determine the age limit for a safe insertion of 3.5-mm screws into the lateral masses according to our own limiting parameters. MATERIALS AND METHODS: Dimensions of the atlas were measured on 200 CT scans of the craniocervical junction in individuals aged 0-18 years and on 34 anatomical specimens of the first cervical vertebra (aged 2.5-18 years). Both series were divided according to the gender and age. The values measured on CT scans were used for statistical comparison of data in boys and girls and comparison of the right and left sides. RESULTS: The atlas reaches its maximum growth rate between 0 and 2 years of age, then the growth decelerates and continues until the age of 18 years. The proportion of dimensions of C1 vertebral foramens changes with age. The youngest children show a relatively greater distance from the left to the right medial pedicle; around the age of 5 the values get even and subsequently the distance from the inner wall of anterior to posterior arch gets relatively greater. The transverse foramen has a slightly oval shape throughout the period of growth. Statistically significant differences between boys and girls were observed primarily between 12 and 18 years of age. CONCLUSION: The study has proved adequate size of lateral masses for insertion of 3.5-mm screws in all patients from the age of 5 years. In younger children, the patient´s anatomy should be respected and the surgical technique tailored accordingly.

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Atlas and axis instrumentation may be necessary in cases of several craniocervical junction pathologies. According to the Harms technique, C1-C2 polyaxial screws are inserted respectively in the C1 lateral masses and in C2 pedicles. C1 lateral mass screw insertion requires the careful subperiosteal dissection of the posterior elements of C1, the identification of the screw entry point by the downward distraction of C2 nerve root, and the cautious sparing of the overlying posterior external vertebral venous plexus (peVVP), whose bleeding, obstructing the surgical field, is sometimes barely controlled by hemostatic agents and swabbing. The authors describe in detail the anatomical aspects of an alternative surgical technique developed for the microsurgical transposition of the C1-C2 interposed external vertebral venous plexus in the case of Harms C1-C2 screw stabilization. The longitudinal median incision of the atlantoaxial membrane, followed by bilateral subperiosteal dissection and microsurgical section respectively at the inferior borders of the C1 laminae and at the superior borders of the C2 laminae, allows, as a "window opening," the symmetrical mediolateral transposition of the peVVP. This procedure provides a faster and cleaner anatomical exposition of the posterior surface of the C1 lateral mass and the C2 isthmus, preventing troublesome intraoperative venous bleeding that hinders C1 lateral mass screw insertion.

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Cervical spondylosis is the leading cause of cervical myelopathy. When surgery is indicated, it is commonly addressed through an anterior or posterior cervical approach, such as cervical discectomy and fusion (ACDF) or laminectomy and fusion (LMF). Besides their own merits, each one has specific approach- or device-related complications, such as dysphagia, significant postoperative pain, wound infection, adjacent segment degeneration (ASD), and pseudoarthrosis. Through a tissue-sparing minimally invasive technique, posterior cervical fusion (PCF) has shown unfolding compelling evidence of biomechanical stability, good clinical outcomes, and high fusion rates, with fewer complications and better econometrics. On the basis of our own experience, we discuss here the indications, advantages, and drawbacks of minimally invasive PCF.

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BACKGROUND: In surgery for cervical spondylotic myelopathy (CSM) with spondylolisthesis, there is no consensus on the correction and fixation for spondylolisthesis. The authors retrospectively studied whether the correction of single-level fixation with lateral mass screws (LMSs) could be maintained. OBSERVATIONS: The records of patients with CSM with spondylolisthesis who had been treated with posterior decompression and single-level fusion with LMSs from 2017 to 2021 were retrospectively reviewed. Radiographic measurements included cervical parameters such as C2-7 lordosis, T1 slope, and the degree of spondylolisthesis (percent slippage) before surgery, immediately after surgery, and at the final observation. Ten cases (mean age 72.8 ± 7.8 years) were included in the final analysis, and four cases (40%) were on hemodialysis. The median observation period was 26.5 months (interquartile range, 12-35.75). The mean percent slippage was 16.8% ± 4.7% before surgery, 5.3% ± 4.0% immediately after surgery, and 6.5% ± 4.7% at the final observation. Spearman's rank correlation showed a moderate correlation between preoperative slippage magnitude and correction loss (r = 0.659; p = 0.038). Other parameters showed no correlation with correction loss. LESSONS: For CSM with spondylolisthesis, single-level fixation with LMSs achieved and maintained successful correction in the 2-year observation.

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Background: Type 2 odontoid fractures with posterior displacement are rare. Most acute cases reported in the literature are readily reduced with traction alone. Here, we reviewed the management of a chronic, posteriorly displaced odontoid fracture that was managed with a unique posterior reduction maneuver. Case Description: A 58-year-old male with a chronic type 2 retro-odontoid displaced fracture was managed with traction and an anterior force applied to the displaced odontoid fragment using rods attached to bilateral C1 lateral mass screws. Notably, this included a simultaneous cantilever maneuver using a lever placed between the C1 and C2 facet joints. Following reduction, an atlantoaxial fusion was performed. The postoperative course of the patient was uneventful and the bone union was achieved in 1 year. Conclusion: Closed reduction is rarely successful in chronic posteriorly displaced type 2 odontoid fractures. These cases require meticulous open reduction and fixation.

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INTRODUCTION AND IMPORTANCE: Traumatic subluxation of C2-C3 with Atlanto-Axial dislocation is very rare and uncommon condition. Only a very few case reported. What constitutes appropriate management in cases of traumatic C2-C3 subluxation with Atlato-axial dislocation is still controversial due to the infrequency of this injury. We managed a patient who had traumatic C2-C3 subluxation with Atlanto-axial dislocation following a history of trauma through posterior approach successfully. CASE DESCRIPTION: A 45-year male day laborer presented with neck pain with progressive neurological deficit after two episodes of fall with heavy object within 1 year. Imaging revealed complete dislocation of C2 over C3 with Atlanto-Axial Dislocation. The patient was approached for posterior fixation with attempt to reduction per-operatively with skeletal traction and C1, C2, C3 joint distraction. After distraction of the joint, we achieved to do reduction of the C2-C3 and Atlanto-Axial joint. We did C1 lateral mass, C2 pedical and C3, C4 lateral mass screw and put a spacer in between C1-C2 facet joint. The patient was improved immediately after the operation. One year follow up shows, he was completely well. One year follow up shows in radiography proper alignment with fusion between C1, C2 and C3. CLINICAL DISCUSSION: Traumatic subluxation of the C2 vertebra is due to fractures of the lamina, articular facets, pedicles, or pars interarticularis and was first described by Bouvier in1843. To the best of our knowledge there has been 3/4 cases reported till now with traumatic C2-C3 subluxation with AAD. In three similar cases before ours, one was reported to be reduced after 3 weeks of bidirectional cervical traction and another two cases were managed by open reduction and stabilization. We managed this rare case surgically successfully through posterior approach with good outcome. CONCLUSION: Our management through posterior approach between C1 to C4 shows very good outcome with proper fusion. But it needs proper understanding the anatomy and mechanism of reduction by careful reading the image. Its needs more case description and management to establish a standard treatment for this type of disease.