C1 Lateral Mass Research Articles

CT imaging analysis of the C7 pedicle and lateral mass in children aged 0–14 years

Background and objectiveThere is currently a lack of anatomical research on the C7 pedicle and lateral mass in children aged 0–14 years, and experience with pediatric lower cervical spine surgeries remains limited. This study aims to investigate the anatomical structure of the C7 pedicle and lateral mass in a large pediatric sample to understand their growth patterns, providing imaging and anatomical references for pediatric lower cervical spine surgeries and the design of pediatric C7 screws. MethodsWe measured 12 parameters, including the width, length, height, and angles of the C7 pedicle and lateral mass in children aged 0–14 years. The t-test was used to analyze bilateral and gender differences, and least squares regression was applied for curve fitting analysis. ResultsThe size parameters of the C7 pedicle and lateral mass generally increased with age, while angular parameters fluctuated within specific ranges. The average values for each parameter between ages 0–14 were as follows: D1: 2.78–5.28 mm, D2: 18.15–30.54 mm, D3: 2.44–6.01 mm, angle A: 38.05–44.48°; D4: 6.81–10.94 mm, D5: 5.37–11.23 mm, D6: 8.07–13.28 mm, D7: 1.94–4.88 mm, D8: 5.67–9.39 mm, angle C: 18.50–28.80°, angle D: 43.23–52.01°, angle E: 33.74–44.96°. Bilateral analysis showed no significant differences for most parameters across most age groups, with differences mainly observed in angle A, angle C, D6, and D8. Gender differences were primarily noted in length parameters across different age groups, especially in the 3–4, 6–7, 9–11, and 13–14 age groups. Regression analysis indicated that most parameters followed cubic function curves, while a few followed power or quadratic function curves. ConclusionThis study provides detailed CT imaging anatomy of the C7 pedicle and lateral mass in children aged 0–14 years. Preoperative thin-slice CT scans and careful measurements of key parameters are essential for pediatric lower cervical spine surgeries. The findings offer valuable imaging and anatomical references for pediatric posterior cervical fixation surgery and screw design.

Migration of cervical spine screws to the sacral canal: a case report

Cervical open door laminoplasty is widely used in multilevel decompression, which is a motion-sparing decompression treatment option for multilevel cervical myelopathy. Implant distance migration in cervical laminoplasty has not been reported. A 61-year-old woman underwent cervical laminoplasty, three months postoperatively, she experienced left shoulder pain and left upper limb pain, and underwent cervical magnetic resonance imaging, which showed no abnormalities. She gradually developed dizziness, headache, unstable walking, incomplete urinary incontinence, and fluctuating neck lumps. The X-ray showed that the screws of the C7 lateral mass had disappeared and migrated to the sacral canal. The patient underwent cerebrospinal leakage repair and removal of the screws in the spinal canal. Displacement of fixators implanted into the spinal canal after cervical laminoplasty is a rare complication that can cause permanent neurological injury.

Biomechanical differences of three cephalic fixation methods for patients with basilar invagination and atlantoaxial dislocation in the setting of congenital atlas occipitalization: a finite element analysis

Background contextIn cases of basilar invagination-atlantoaxial dislocation (BI-AAD) complicated by atlas occipitalization (AOZ), the approach to cranial end fixation has consistently sparked debate, generally falling into two categories: C1–C2 fixation and occipitocervical fixation. Several authors believe that C1–C2 fixation carries a lower risk of fixation failure than occipitocervical fixation. PurposeTo study the biomechanical differences among 3 different cranial end fixation methods for BI-AAD with AOZ. Study designThis was a finite element analysis. Patient sampleA 35-year-old female patient diagnosed with congenital BI-AAD and AOZ. Outcome measuresrange of motion (ROM), peak von Mise stress (PVMS), cage micro-subsidence, cage micro-slippage MethodFour finite element models were constructed, including unstable group (BI-AAD with AOZ), C1 lateral mass screw group, occipital plate group, occipitocervical rod group. The flexion and extension (FE), lateral bending (LB) as well as axial rotation (AR) were simulated under a torque of 1.5 Nm. Parameters include C1–C2 ROM, PVMS on screw-rod construct, cage micro-subsidence, cage micro-slippage. ResultsThe ROM of the C1 lateral mass screw group was smaller than that of the other fixation groups in LB and AR, but not FE. Compared with the occipitocervical rod group, the ROM in LB and AR of the occipital plate group was higher, but not in FE. The PVMS of C1 lateral mass screw group was significantly higher than that of the other groups. The ROM and PVMS of the occipitocervical rod group were in between the other 2 groups. Regarding the screws at the cranial end, the PVMS of the 4-screw occipitocervical rod group was significantly lower than that of the other groups. In general, the cage micro-motion follows the ascending order: C1 lateral mass group < occipitocervical rod group < occipital plate group. ConclusionIn cases of BI-AAD with AOZ, the C1 lateral mass screw group provided the least ROM and cage micro-motion, but the screw-rod PVMS was the largest. The advantage of occipital plate fixation lies in the lowest screw-rod PVMS, but the ROM and cage micro-motion is the highest. Four-screw fixation at the cranial end of occipitocervical rod group helps to reduce the PVMS and may prevent screw failure at the cranial end.

Novel Delivery of Cryoablation Through Transoral Surgical Approach for Atypical Presentation of Osteoid Osteoma of the C1 Lateral Mass: Technical Case Illustration

BACKGROUND AND IMPORTANCE: Neurosurgical literature rarely explores cases of osteoid osteomas of the atlas. Traditionally, neurosurgeons performed en bloc surgical resection for refractory osteoid osteomas in the subaxial and lumbar spine, but minimally invasive ablation therapies have gained favor. Complete lesioning of the nidus, either by surgical or minimally invasive therapies, produces curative results with recurrence only developing after partial lesioning. CLINICAL PRESENTATION: We discuss the case of a 16-year-old adolescent boy who presented with neck and occipital pain refractory to multimodal pain management. Prolonged workup demonstrated a subtle radiographic lesion of the left C1 lateral mass. Interventional radiologists attempted a posterior approach percutaneous computed tomography-guided radiofrequency ablation but aborted due to proximity of the vertebral artery. Surgeons then pursued an open transoral approach to provide a corridor for cyclical cryoablation therapy, which proceeded without complication. The patient was discharged on postoperative day one with remission of occipital pain at the 10-month follow-up. No clinical or radiographic evidence of instability appeared on postoperative cervical films. CONCLUSION: No reports exist in the literature of an osteoid osteoma of C1 treated by an open anterior approach and with cryoablation. The transoral approach is a safe, effective method to access ventral pathologies of C1. The transoral approach may minimize blood loss and reduce the risk of craniocervical instability, allowing for preserved cervical mobility and improved patient outcomes. Surgeons may especially consider cryoablation when the nidus is within proximity to critical neural structures.

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.

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.

Unilateral high-riding vertebral artery is associated with asymmetric morphological changes of the atlantoaxial joint: a novel risk factor for atlantoaxial osteoarthritis.

This study aimed to investigate the association between unilateral high-riding vertebral artery (HRVA) and morphological changes in the atlantoaxial joint (AAJ) and to determine whether unilateral HRVA is a risk factor for atlantoaxial osteoarthritis (AAOA). We conducted a retrospective analysis of 2496 patients admitted to our medical center between January 2020 and December 2022 who underwent CT imaging of the cervical spine. Two hundred and seventy-two patients with unilateral HRVA (HRVA group) were identified and a respective 2:1 age- and sex-matched control group without HRVA was built. Morphological parameters, including C2 lateral mass settlement (C2 LMS), C1/2 coronal inclination (C1/2 CI), lateral atlanto-dental interval (LADI), and C1/2 relative rotation angle (C1/2 RRA) were measured. The degree of AAOA was recorded. Risk factors associated with AAOA were identified using univariate and multivariable logistic regression analyses. The study included 61.4% women, and the overall average age of the study population was 48.7years. The morphological parameters (C2 LMS, C1/2 CI, and LADI) in AAJ were asymmetric between the HRVA and the non-HRVA sides in the HRVA group (p < 0.001). These differences in parameters (d-C2 LMS, d-C1/2 CI, and d-LADI) between the HRVA and the non-HRVA sides, and C1/2 RRA were significantly larger than those in the control group. Eighty-three of 816 patients (10.2%) with AAOA had larger values of d-C2 LMS, d-C1/2 CI, d-LADI, and C1/2 RRA compared with the patients without AAOA (p < 0.05). The multivariable logistic regression analysis indicated that unilateral HRVA [adjusted odds ratio (OR) = 2.6, 95% CI: 1.1-6.3, p = 0.029], age in the sixth decade or older (adjusted OR = 30.2, 95% CI: 16.1-56.9, p < 0.001), women (adjusted OR = 2.1, 95% CI: 1.0-5.6, P = 0.034) were independent risk factors for AAOA. Unilateral HRVA was associated with asymmetric morphological changes of nonuniform settlement of C2 lateral mass, lateral slip of atlas, and atlantoaxial rotation displacement. Besides age ≥ 60years and females, unilateral HRVA is an independent risk factor for AAOA.

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.

Posterolateral Paramass Approach to Lesions Located at the Anterior C1-2 Level: A Cadaver Study

A novel posteriolateral surgical approach is described that will provide safe access to intradural and extradural lesions located in the anterior part of the spinal cord (SC) at the C1-2 level and to the odontoid in single session. A total of five cadavers and two dry C1 vertebrae were used in this study. The study involved obtaining computed tomography magnetic resonance imaging scans and magnetic resonance imaging of all cadaver groups before and after the procedures. Group 1: Control; Group 2: Unilateral C1 posterior arch was removed, the inferomedial part of C1 lateral mass was removed, and access the anterior and lateral aspects of the SC. Group 3: In addition, odontoid was removed, Group 4: In addition, unilateral C1- C2 screw was placed. Group 5: In addition, bilateral C1-C2 screw was placed. The median distance from the midpoint of C1 posterior tubercle to vertebral groove which was removed in groups is 21.4 ± 2.88mm. The average width of C1 lateral mass was 13.4±2.4mm. After the lateral mass was drilled, its width decreased to 10,2mm.This area was sufficient to open a surgical corridor and reach the anterior of SC and odontoid. After the procedure, no instability was found in group 2 without instrumentation on computed tomography and magnetic resonance imaging scans. It is possible to access the anterior C1-C2 via a posterolateral paramass approach by drilling 20%-30% of the lateral mass, providing an open pathway for easy intervention in C1-C2 intradural lesions. It is also possible to perform odontoid resection using this approach.

Perioperative complications associated with fluoroscopy C1 lateral mass screw fixation (Goel technique) versus computed tomography-guided navigation technique: A review of 202 cases from the German Spine Registry (DWG-Register).

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. 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. 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%). 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.

Evaluation of Craniometric Parameters and Efficacy of Posterior Surgical Intervention Types in Basilar Invagination Patients

OBJECTIVEBasilar invagination is one of the most frequently observed abnormalities at the craniovertebral junction, in which the odontoid process of C2 prolapses into the foramen magnum. METHODSThe current study included 27 patients who underwent surgery for basilar invagination between October 2013 and January 2023. The study group was divided into 2 groups according to basilar invagination types; type I (the presence of type A atlantoaxial instability and instability is the main pathology) and type II (the presence of type B and C atlantoaxial instability and skull base dysgenesis is the main pathology). Craniometric parameters included in the study were; atlantodental interval, posterior atlantodental interval, Chamberlain’s line violation, clivus-canal angle, Welcher’s basal angle, and Boogaard angle. RESULTSThe mean age of the patients was 24.30 ± 14.36 years (5-57 years). Fourteen patients (51.9%) were female, and 13 patients (48.1%) were male. Ten patients (37%) had type I basilar invagination, 17 patients (63%) had type II basilar invagination. Preoperative and postoperative atlantodental interval and Boogaard angle were significantly higher in type I basilar invagination, as preoperative and postoperative posterior atlantodental interval and clivus-canal angle were significantly higher in type II basilar invagination. There was a positive strong correlation between Chamberlain‘s line violation and Boogaard angle. Postoperative Chamberlain‘s line violation was significantly higher in occipitocervical fixation (p=0.035). C1 lateral mass screw fixation was found more successful in Chamberlain‘s line violation correction than occipital plates. Occipitocervical fixation was found to be associated with higher postoperative Nurick scores (p=0.015) and complication rates (p=0.020). Cages applied to the C1-C2 joint space were found to be associated with higher fusion rates (p = 0.023) and lower complication rates (p = 0.024). CONCLUSIONSIn the present study, it was found that C1-C2 fixation was more successful in correcting craniometric parameters and had lower complication rates than occipitocervical fixation. In appropriate patients, it was determined that cage application increased the success rates of the operations.

A novel classification and management scheme for craniocervical junction disorders with ventral neural element compression.

Craniocervical junction (CCJ) pathologies with ventral neural element compression are poorly understood, and appropriate management requires accurate understanding, description, and a more uniform nomenclature. The aim of this study was to evaluate patients to identify anatomical clusters and better classify CCJ disorders with ventral compression and guide treatment. A retrospective review of adult and pediatric patients with ventral CCJ compression from 2008 to 2022 at a single center was performed. The incidence of anatomical abnormalities and compressive etiologies was assessed. Surgical approach, radiographic data, and outcomes were recorded. Association rules analysis (ARA) was used to assess variable clustering. Among 51 patients, the main causes of compression were either purely bony (retroflexed dens [n = 18]; basilar invagination [BI; n = 13]) or soft tissue (degenerative pannus [n = 16]; inflammatory pannus [n = 2]). The primary cluster in ARA was a retroflexed dens, platybasia, and Chiari malformation (CM), and the secondary cluster was BI, C1-2 subluxation, and reducibility. These, along with degenerative pannus, formed the three major classes. In assessing the optimal treatment strategy, reducibility was evaluated. Of the BI cases, 12 of the 13 patients had anterolisthesis of C1 that was potentially reducible, compared with 2 of the 18 patients with a retroflexed dens (both with concomitant BI), and no pannus cases. The mean C1-2 facet angle was significantly higher in BI at 32.4°, compared with -2.3° in retroflexed dens and 8.1° in degenerative pannus (p < 0.05). Endonasal decompression with posterior fixation was performed in 48 (94.0%) of the 51 patients, whereas posterior reduction/fixation alone was performed in 3 patients (6.0%). Of 16 reducible cases, open posterior reduction alone was successful in 3 (60.0%) of 5 cases, with all successes containing isolated BI. Reduction was not attempted if vertebral anatomy was unfavorable (n = 9) or the C1 lateral mass was absent (n = 5). The mean follow-up was 28 months. Symptoms improved in 88.9% of patients and were stable in the remaining 11.1%. Tracheostomy and percutaneous G-tube placement occurred in 7.8% and 11.8% of patients, respectively. Reoperation for an endonasal CSF leak repair or posterior cervical wound revision both occurred in 3.9% of patients. In classifying, one cluster caused decreased posterior fossa volume due to an anatomical triad of retroflexed dens, platybasia, and CM. The second cluster caused pannus formation due to degenerative hypertrophy. For both, endonasal decompression with posterior fixation was ideal. The third group contained C1 anterolisthesis characterized by a steep C1-2 facet angle causing reducible BI. Posterior reduction/fixation is the first-line treatment when anatomically feasible or endonasal decompression with in situ posterior fixation when anatomical constraints exist.

Robotic-Assisted and Computer-Assisted Navigation Surgery in the Cervical Spine: Current Experiences, Techniques, and Accuracy

Background: In recent years, the role of robotic-assisted and computer-assisted navigation (RA-CAN) systems has significantly expanded in spine surgery, particularly those performed in the thoracic, lumbar and sacral spine showing higher accuracy in pedicle screw placement and improved surgical efficiency. However, there are few reports on these techniques in the cervical spine. The anatomy of the cervical spine possesses additional challenges such as the close proximity to critical neurovascular structures. Purpose: In this article, we present the existing clinical experience of RA-CAN in the cervical spine and evaluate technical considerations. Cervical spine screw fixation and decompression using RA-CAN are reviewed. Results: This analysis covers various aspects such as techniques, accuracy, and the types of procedures reported in the literature. Recent reports include surgical procedures such as anterior cervical diskectomy and fusion’s, odontoid fracture fixation, C1 lateral mass, C2 pedicle, translaminar, subaxial spine lateral mass, and mid-cervical spine pedicle screw fixation. There is potential for enormous clinical benefit to navigated decompression in cervical CAN procedures also. Future opportunities include further improvements in imaging co-localization, pre-surgical planning software, and mechanization of surgical procedures for instrumentation and decompression. Conclusion: The growth of RA-CAN in spinal surgery has shown significant potential in its application in the cervical spine for fusion procedures as well as decompression. By understanding the potential limitations and techniques reported from early experiences, previous techniques can be improved and provide further benefits for accuracy and less invasive surgery.

Craniovertebral Junction Surgical Approaches: State of Art.

Surgical approaches directed toward craniovertebral junction (CVJ) can be addressed to the ventral, dorsal, and lateral aspects through a variety of 360° surgical corridors Herein, we report features, advantages, and limits of the updated technical support in CVJ surgery in clinical setting and dissection laboratories enriched by our preliminary surgical results of the simultaneous application of O-arm intraoperative neuronavigation and imaging system along with the 3D-4K EX in TOA for the treatment of CVJ pathologies.In the past 4years, eight patients harboring CVJ compressive pathologies underwent one-step combined anterior neurosurgical decompression and posterior instrumentation and fusion technique with the aid of exoscope and O-arm. In our equipped Cranio-Vertebral Junction Laboratory, we use fresh cadavers (and injected "head and neck" specimens) whose policy, protocols, and logistics have already been elucidated in previous works. Five fresh-frozen adult specimens were dissected adopting an FLA. In these specimens, a TOA was also performed, as well as a neuronavigation-assisted comparison between transoral and transnasal explorable distances.A complete decompression along with stable instrumentation and fusion of the CVJ was accomplished in all the cases at the maximum follow-up (mean: 25.3months). In two cases, the O-arm navigation allowed the identification of residual compression that was not clearly visible using the microscope alone. In four cases, it was not possible to navigate C1 lateral masses and C2 isthmi due to the angled projection unfitting with the neuronavigation optical system, so misleading the surgeon and strongly suggesting changing surgical strategy intraoperatively. In another case (case 4), it was possible to navigate and perform both C1 lateral masses and C2 isthmi screwing, but the screw placement was suboptimal at the immediate postoperative radiological assessment. In this case, the hardware displacement occurred 2months later requiring reoperation.

Database Review of 514 Patients with Os Odontoideum. Detailed Analysis of 258 Surgically Treated (1978-2019).

Database review (1978-2019) is to identify the cause of os odontoideum, its presentation, associated abnormalities, and management recommendations. Review of referral database of 514 patients and 258 surgically treated patients ages 4-64years. Detailed history of early childhood trauma and initial encounter record retrieval were made. Patients had dynamic motion radiographs, dynamic motion MRI and also CT to identify pathology and reducibility of craniocervical instability. Preoperative crown halo traction was made before the year 2000 except in children. Intraoperative traction with O-arm/CT documentation was made since 2001. Reducible and partially reducible cases underwent halo traction under general anesthesia distraction, dorsal stabilization, and rib graft augmentation for fusion. Later semi-rigid instrumentation and subsequently rigid instrumentation was made. Irreducible compression of cervicomedullary junction was treated with ventral decompression. The follow up was 3-20years. Database; acute worsening after trauma 262, insidious neurological deficit 252. Minimal/normal motion with neurological deficit was present in 18, previous C1-C2 fusion with worsening in 18. 28 patients of 64 without treatment worsened in 4years. An intact odontoid process was seen in 52 children of 156 who had early craniovertebral junction trauma and later developed os odontoideum. There were 174 patients with reducible lesions and partially reducible were 22. Irreducible lesions were 62. Of the reducible, 50 underwent transarticular C1-C2 fusion, 26 C1 lateral mass, and C2 pars screw fixation. 182 had occipitocervical fusion (19 had extension of previous C1-C2 fusion and 43 after transoral decompression). 62 with irreducible ventral compression of the cervicomedullary junction underwent transoral decompression; 43 had a trapped transverse ligament between the os and C2 body and 19 previous C1-C2 fusions. Compression was by the axis body, os odontoideum, and the posterior C2 arch. Syndromic and skeletal/connective tissue abnormalities were found in 86 (36%). 2 patients worsened, age 10 and 62, due to failure of semi-rigid construct. The etiology of os odontoideum is multifactorial considering the associated abnormalities, reports of congenital-familiar occurrence, and early childhood craniovertebral trauma which also plays a role in the etiology. Patients with reducible lesions require stabilization. Asymptomatic patients are at risk for later instability. Patients who underwent childhood C1-C2 fusion must be followed for later problems. The irreducibility was seen due to trapped transverse ligament, pannus, or previous dorsal C1-C2 fusion.

C1 Lateral Mass-C2 Pars Fixation in Occipitalized Atlas with Fenestrated V3 Vertebral Artery-Operative Nuances Step by Step (Video Section).

C1 Lateral Mass-C2 Pars Fixation in Occipitalized Atlas with Fenestrated V3 Vertebral Artery-Operative Nuances Step by Step (Video Section).

C2 Superior Facetal Osteotomy: A Novel Technique in Complex Craniovertebral Junction Surgery for C1 Lateral Mass Screw Placement.

Complex craniovertebral junction (CVJ) defects account for a considerable proportion of CVJ diseases. Given the heavily assimilated C1, an unfavorable C1-C2 joint orientation, an overriding C2 superior facet, a low-hanging occiput, and an abnormal vertebral artery course with a high-riding vertebral artery, placement of C1 lateral mass screws might be difficult. To address this, a novel technique for placing C1 lateral mass screws that avoid vertebral artery injury, low-hanging occiput, and overriding C2 superior facet was developed in this study. This approach enables firm fixation of C1-C2 even in difficult situations where the placement of the C1 lateral mass is challenging.

Midpoint of C7 Lateral Mass Serves as an Accurate Reference Point for the Placement of T1 Pedicle Screws: An Anatomic Study.

Free-hand placement of T1 pedicle screws can often be challenging. A reliable free-hand technique for placement of T1 pedicle screws can overcome some of the difficulties associated with poor fluoroscopy in this region. The purpose of this study was to propose a novel anatomic landmark for accurate identification of the T1 entry point using the midpoint of the C7 lateral mass as a reference point. Our hypothesis is that the midpoint of the C7 lateral mass is within 1-2 mm of the center of the T1 pedicle. Using 3-dimensional reconstruction software, the pedicle of T1 and the lateral mass of C7 were isolated to assess the location of the T1 pedicle relative to the C7 lateral mass. Specifically, the distance between the center of the T1 pedicle and the center of the C7 lateral mass was measured on 40 computed tomography scans. Furthermore, a clinical validation of this technique was performed by assessing the postoperative computed tomography scans of 53 patients undergoing cervicothoracic instrumentation. The Gertzbein and Robbins classification system was used to grade the accuracy of T1 pedicle screw placements in all patients using this technique. The average horizontal deviation + SD from centers of the T1 pedicle and the C7 lateral mass was 0.398 mm ± 0.953 mm. The T1 pedicle on average was slightly medial to the center of the C7 lateral mass. A total of 98.1% of T1 pedicle screws placed in vivo using the free-hand technique were of Grade A. In this article, we demonstrate that the center of the C7 lateral mass overlays the T1 pedicle and the optimal entry point is immediately below the midpoint of the C7 lateral mass. This approach provides a practical and accurate landmark in posterior cervicothoracic spine procedures that reduce the need for additional radiation exposure or increased operative time with image-guided techniques.