Challenges in Occipitocervical Fusion in a 9-Month-Old Infant: A Case Report and Review of Literature.

ABSTRACT: Traumatic cranio-cervical junction injuries in infants are rare and require early surgical stabilization. In view of the unique anatomy of the occipitocervical junction in infants, the creation of a fusion construct that is both safe and biomechanically sound is challenging. A 9-month-old male infant involved in an accident presented with weakness in both upper limbs. Imaging revealed a displaced odontoid synchondrosis fracture with combined occipitocervical and atlantoaxial dissociation. Due to the unstable nature of the injury, occiput to C2 arthrodesis using dual distal radius locking plates and autologous full-thickness parietal region calvarial bone graft was performed. Minerva jacket was applied. Computed tomography (CT) scan obtained at 12 weeks demonstrated evidence of bony fusion. Combined injuries to the occipitocervical and atlantoaxial joint in an infant can be fatal. A thorough assessment of multiple imaging modalities helps to make an early and accurate diagnosis.

"Letter to the editor: traumatic atlantoaxial rotatory fixation in adults: a systematic review of published cases".

This critique evaluates a recent study on adult traumatic atlantoaxial rotatory fixation (AARF), focusing on its strengths, weaknesses, and suggestions for future research. The study provides a comprehensive examination of the anatomical and biomechanical complexities of the C1-C2 articulation, shedding light on the rare nature of adult traumatic AARF and common injury mechanisms. It categorizes AARF based on the atlanto-dental interval (ADI) and dislocation severity, aiding clinicians in assessing injury severity and treatment planning. Furthermore, the study explores conservative and surgical management approaches, offering valuable insights into treatment decision-making and outcomes. However, limitations such as its retrospective nature, reliance on reported cases, lack of standardized protocols, and limited sample size may constrain the generalizability of findings. Future research should prioritize prospective, multicenter studies with standardized protocols, collaborative efforts among institutions, and innovative techniques to advance our understanding and management of adult traumatic AARF.

Relationship between clinical parameters and malformations in dogs diagnosed with atlanto-axial instability.

Atlanto-axial instability is a common disease that affects toy-breed dogs. Most cases of atlanto-axial instability are congenital. Furthermore, patients with atlanto-axial instability are predisposed to other concurrent diseases. Therefore, this study aimed to retrospectively determine the presence of concurrent diseases in cases with atlanto-axial instability using imaging data and analyze the relationship between clinical parameters and the incidence of complex malformations. The clinical data and imaging findings of 41 toy-breed dogs diagnosed with atlanto-axial instability were analyzed using their medical records and imaging data. Occipital dysplasia (17/27), atlanto-occipital overlapping (22/34), dens dysplasia (27/41), Chiari-like malformation (8/34), syringomyelia (5/34), lateral ventricular enlargement (20/36), and intracranial arachnoid cyst (5/35) were observed in patients with atlanto-axial instability. The body weight of the patients in the groups with atlanto-occipital overlapping and lateral ventricular enlargement was lower than that of those in the groups without these diseases (1.78 ± 0.71 vs 2.71 ± 1.15 kg, P = 0.0269, 1.60 ± 0.40 vs 2.75 ± 1.08 kg, P = 0.001, respectively). Furthermore, when the correlation between the total number of concurrent diseases and the age at onset and body weight was examined, it became clear that lower body weight was associated with the incidence of a greater number of concurrent diseases. Thus, the findings of this study suggest that toy-breed dogs are more likely to present with complex malformations and should be evaluated carefully with additional examinations and treatment methods.

Design of a novel lateral mass screw-plate system for the treatment of unstable atlas fractures: a finite element analysis.

BACKGROUND: Osteosynthesis of unstable atlas fractures preserves joint motion and therefore has a distinct advantage over a range of treatment procedures. To prevent the potential disadvantages associated with osteosynthesis, a new atlas lateral mass screw-plate (LMSP) system has been designed. However, the biomechanical role of using the LMSP system in atlas internal fixation is not known. The aim of this study was to compare the biomechanical stability of a new LMSP with traditional posterior screw and rod (PSR) fixation techniques on the occipitocervical junction (C0-C2) through finite element analysis. METHODS: A nonlinear C0-C2 finite element model of the intact upper cervical spine was developed and validated. The unstable model using the PSR system was then compared with the model using the LMSP system for fixation. A vertical load of 40 N was applied to the C0 to simulate head weight, while a torque of 1.5 Nm was applied to the C0 to simulate flexion, extension, lateral bending, and axial rotation. RESULTS: The range of motion of both systems was close to the intact model. Compared with the LMSP system model, the PSR system model increased flexion, extension, lateral bending, and axial rotation by 4.9%, 3.0%, 5.0%, and 29.5% in the C0-C1 segments, and 4.9%, 2.7%, 2.4%, and 22.6% in the C1-C2, respectively. In flexion, extension, and lateral bending motion, the LMSP system model exhibited similar stress to the PSR system model, while in axial rotation, the PSR system model exhibited higher stress. CONCLUSIONS: The findings of our study indicate that the two tested system models provide comparable stability. However, better stability was achieved during axial rotation with the LMSP system, and in this system, the maximum von Mises stress was less than that of the PSR one. As the atlantoaxial joint functions primarily as a rotational joint, the use of the LMSP system may provide a more stable environment for the joint that has become unstable due to fracture.

Early Outcomes of Bone Autografting in the Bilateral Atlantoaxial Joints Applied in Posterior Fusion Surgery.

OBJECTIVE: Cable-dragged reduction and cantilever beam internal fixation can provide promising results in the treatment of atlantoaxial dislocation or instability. However, bilateral atlantoaxial joints bone autografting has not been conducted in this technique. We aim to evaluate the safety and effectiveness of bilateral atlantoaxial joints bone autografting in posterior cable-dragged reduction and cantilever-beam internal fixation. METHODS: In this retrospective study, we included 14 patients with a minimum 24-month follow-up from December 2019 to September 2020. The granular bone harvested from the iliac crest was packed into the bilateral atlantoaxial joints of 14 patients in posterior cable-dragged reduction and cantilever-beam internal fixation. X-ray imaging and cervical computed tomography (CT) were performed during follow-up. The time required for bone fusion was recorded. The clinical outcomes were evaluated using the JOA scores, NDI, and VAS scores. Mann-Whitney U test, the chi-squared test, or the Fisher exact test were used to compare the two groups regarding patient characteristics, clinical outcomes, bone fusion rates, and cervical sagittal alignment. RESULTS: The operations were successfully performed in all patients without any intraoperative complications. The mean operation time was (169.64 ± 20.91) minutes, and the intraoperative blood loss was (130.71 ± 33.62) mL. All patients received satisfactory reductions and firm bony fusion at the final follow-up. The fusion rates were 64.29% in the atlantoaxial joints and 21.43% in post bone graft area at 3 months postoperatively, and a significant difference was observed (p = 0.022). Besides, the cervical sagittal alignment in all patients was well maintained in the last follow-up compared to preoperatively. Importantly, a complete bony fusion in the atlantoaxial joints was observed in all patients. Moreover, the JOA, NDI, and VAS scores had improved significantly at the last follow-up. CONCLUSION: Bone autografting of the bilateral atlantoaxial joints is a safe and effective technique to increase bone fusion rates, shorten bone fusion time, and reduce complication rates when the cable-dragged reduction and cantilever beam internal fixation approach is used. Therefore, it is a cost-effective surgical procedure for treating patients with atlantoaxial dislocation or instability.

[Advances in the technology of surgical treatment for atlantoaxial dislocation].

The etiology and pathological morphology of atlantoaxial dislocation (AAD) are complex. Based on the pathological anatomical characteristics of AAD, combined with clinical techniques, it is essential to formulate reasonable classification criteria and develop corresponding treatment strategies for different types of AAD. The satisfactory outcome of surgical treatment for AAD can only be achieved through the comprehensive application of various atlantoaxial reduction techniques, tension band releasing techniques, internal fixation and fusion techniques. This article discusses the latest advancements in surgical treatment techniques for AAD, thoroughly explores treatment strategies based on different types of AAD, and analyzes the practicality and effectiveness of clinical classification and treatment strategies. The posterior atlantoaxial facet releasing and distraction compression reduction technique may pose challenges to traditional treatment strategies in the future. In the development of surgical treatment techniques for AAD, microspinal surgical techniques may play a significant role in improving surgical methods and enhancing treatment outcomes.

C1-C2 intraarticular distraction with anterior cervical cages for basilar invagination realignment: Operative technique nuances and review of literature.

Neurosurgical management of basilar invagination (BI) has traditionally been aimed at direct cervicomedullary decompression through transoral dens resection or suboccipital decompression with supplemental instrumented fixation. Dr. Goel introduced chronic atlantoaxial dislocation (AAD) as the etiology in most cases of BI and described a technique for distracting the C1-C2 joint with interfacet spacers to achieve reduction and anatomic realignment. We present our modification to Goel's surgical technique, in which we utilize anterior cervical discectomy (ACD) cages as C1-C2 interfacet implants. A young adult male presented to our institution with BI, cervicomedullary compression, occipitalization of C1, and Chiari 1 malformation. There was AAD of C1 over the C2 lateral masses. This reduced some with preoperative traction. He underwent successful C1-C2 interfacet joint reduction and arthrodesis with anterior cervical discectomy (ACD) cages and concomittant occiput to C2 instrumented fusion. BI can be effectively treated through reduction of AAD and by utilizing ACD cages as interfacet spacers.

Myelopathy resulting from degenerative atlantoaxial subluxation.

PURPOSE: To present the clinical features and treatment strategy of degenerative atlantoaxial subluxation (DAAS). METHODS: Patients with DAAS treated in our institution from 2003 to 2020 were retrospectively reviewed. We utilized the Japanese Orthopedic Association (JOA) scale to evaluate the neurologic status and distance of Ranawat et al. (DOR) to measure vertical migration. RESULTS: We recruited 40 patients with > 2 years of follow-up and an average age of 62.3 ± 7.7 years. All the patients had myelopathy; only one patient had moderate trauma before exacerbation of symptoms, and the duration of symptoms was 34 ± 36 months. The most frequent radiological features were vertical migration of C1 (100%), sclerosis (100%), and narrowing of the atlantoaxial lateral mass articulations (100%). Two patients underwent transoral release combined with posterior reduction and fusion, and 38 patients underwent posterior reduction and fusion with C1 lateral mass screws-C2 pedicle screws and plate systems only. Forty cases (100%) achieved a solid atlantoaxial fusion, and 38 cases (95%) achieved anatomic atlantoaxial reduction. The JOA score increased from 9.3 ± 2.6 to 14.8 ± 2.1 (P < 0.01). DOR increased from 14.5 ± 2.5 to 17.8 ± 2.2 mm at the final follow-up (P < 0.01). Loosening of the locking caps was detected in one case, bony fusion was achieved, and harvest-site pain was reported in five patients. CONCLUSION: DAAS differs from other types of AAS and presents with anterior subluxation combined with vertical subluxation arising from degenerative changes in the atlantoaxial joints. We recommend anatomic reduction as an optimal strategy for DAAS.

Craniocervical fusion in the paediatric population - case series of 21 patients.

PURPOSE: Craniocervical junction instability in a paediatric population presents a formidable challenge to the neurosurgeon. With a variety of anatomical variations, diminutive bony and ligamentous structures, possible superimposed syndromic abnormalities, the craniocervical junction is a technically challenging region to operate within. We aimed to review our series of patients to identify the common pathologies necessitating craniocervical fusion along with the use of intraoperative image guidance. METHODS: We performed a retrospective review of twenty-one patients, with a mean age of 8.1 years, undergoing craniocervical fixations, involving either occipitocervical fusion or atlantoaxial fixation, from a single institution over a twelve-year period. The presentation, preoperative investigations, indication for surgery, surgical procedure, use of intraoperative navigation and clinical and radiological results were examined. RESULTS: Twelve patients underwent primary C1-2 fixation, with the remaining 9 undergoing occipitocervical fusion. Five patients underwent surgery for traumatic instability, seven for os odontoideum, six for congenital anomalies and three for post-infectious instability. Follow up for 20 patients averaged 34 months (range 2-93 months). Five patients had Trisomy 21 and all underwent C1-2 fixation. Frameless stereotactic image guidance was utilised in five patients. No patients suffered immediate complications resulting from craniocervical junction fusion. Patients were observed to either neurologically improve (n = 6), or arrest their neurological deterioration following surgical intervention (n = 14), with concomitant radiological evidence of osseous fusion at follow up in 18 of 20 patients (90%). Two patients (10%) had radiological evidence of screw lucency, but neither required intervention because of being asymptomatic. CONCLUSIONS: Craniocervical fixation in a paediatric population is a viable and safe treatment modality for the management of disorders requiring stabilisation at the craniocervical junction. Our experience of utilising frameless stereotaxy in the setting of grossly distorted anatomical landmarks is also reported.

Athrodesis of the lateral atlanto-axial joint for the relief of neck pain and cervicogenic headache.

BACKGROUND: Osteoarthrosis of the lateral atlanto-axial joint (LAAJ) may be a cause of upper neck pain and headache. Intra-articular injection of steroids may provide only short-lasting relief. For intractable pain, arthrodesis of the joint might be considered. OBJECTIVE: To determine the success rates of arthrodesis of the lateral atlanto-axial joint for relieving neck pain and disability. DESIGN: Practice audit. SETTING: Private practice of senior author. SUBJECTS: Prospective series of 23 consecutive patients. METHODS: Outcomes were measured using a numerical rating scale for neck pain, and the Neck Disability Index for disability. Success rates were calculated for various degrees of improvement of neck pain at long-term follow-up (8-40 months), and for achieving various combinations of improvement of both neck pain and disability. RESULTS: Complete relief of pain was achieved in 40% of patients, with a further 40% achieving at least 50% relief. At long-term follow-up, 30% of patients had no neck pain and no disability, and a further 25% had only minimal pain, minimal disability, or both. CONCLUSIONS: The present study did not corroborate earlier studies that claimed outstanding outcomes for arthrodesis of the LAAJ, but its outcomes are consonant with more recent studies that provided transparent outcome data. These studies provide Pain Physicians with empirical data on success rates and outcomes, upon which they can base their consideration of referral for arthrodesis.

C1-C2 Posterior Screw-Rod Fixation.

Multiple approaches for instrumentation of the upper cervical spine have evolved to treat atlantoaxial instability which, until the 20th century, was largely considered to be inoperable and managed nonsurgically with immobilization. Surgeons set out to provide safe and effective approaches in a clearly dangerous and technically complex anatomic region. It is important to provide a historical analysis of the evolution of techniques that have shaped C1-C2 instrumentation, and how the diligent efforts of surgeons to improve the biomechanical stability and fusion rates of their constructs eventually led to the prevailing Harms technique. This technique is explored by describing its surgical steps, alternative techniques, and associated outcomes. For successful instrumentation of the atlantoaxial joint, a comprehensive understanding of spinal biomechanics, surgical techniques, and anatomic variations is imperative for surgeons to develop a tailored plan for each patient's individual pathology and anatomy.

Study on articular surface morphology of atlantoaxial lateral mass based on differential manifold.

OBJECTIVES: To propose a surface reconstruction algorithm based on a differential manifold (a space with local Euclidean space properties), which can be used for processing of clinical images and for modeling of the atlantoaxial joint. To describe the ideal anatomy of the lateral atlantoaxial articular surface by measuring the anatomical data. METHODS: Computed tomography data of 80 healthy subjects who underwent cervical spine examinations at our institution were collected between October 2019 and June 2022, including 46 males and 34 females, aged 37.8 ± 5.1 years (28-59 years). A differential manifold surface reconstruction algorithm was used to generate the model based on DICOM data derived by Vision PACS system. The lateral mass articular surface was measured and compared in terms of its sagittal diameter, transverse diameter, articular surface area, articular curvature and joint space height. RESULTS: There was no statistically significant difference between left and right sides of the measured data in normal adults (P > 0.05). The atlantoaxial articular surface sagittal diameter length was (15.83 ± 1.85) and (16.22 ± 1.57) mm on average, respectively. The transverse diameter length of the articular surface was (16.29 ± 2.16) and (16.49 ± 1.84) mm. The lateral articular surface area was (166.53 ± 7.69) and (174.48 ± 6.73) mm2 and the curvature was (164.03 ± 5.27) and (153.23 ± 9.03)°, respectively. The joint space height was 3.05 ± 0.11mm, respectively. There is an irregular articular space in the lateral mass of atlantoaxial, and both upper and lower surfaces of the articular space are concave. A sagittal plane view shows that the inferior articular surface of the atlas is mainly concave above; however, the superior articular surface of the axis is mainly convex above. In the coronal plane, the inferior articular surface of the atlas is mostly concave above, with most concave vertices located in the medial region, and the superior articular surface of the axis is mainly concave below, with most convex vertices located centrally and laterally. CONCLUSION: A differential manifold algorithm can effectively process atlantoaxial imaging data, fit and control mesh topology, and reconstruct curved surfaces to meet clinical measurement applications with high accuracy and efficiency; the articular surface of the lateral mass of atlantoaxial mass in normal adults has relatively constant sagittal diameter, transverse diameter and area. The distance difference between joint spaces is small, but the shape difference of articular surfaces differs greatly.

[Imaging study on determining the rationality of atlantoaxial fixation angle based on the ratio of line segments between anatomical markers on lateral X-ray films].

Objective: To propose a method to determine the unreasonableness of the fixed angle in posterior atlantoaxial fusion surgery based on the ratio of line segments between anatomical landmarks of the atlantoaxial joint. Methods: A cross-sectional study was conducted. According to the inclusion criteria, a screening was performed on the database of asymptomatic volunteers who had full-spine lateral X-ray films taken at the Second Affiliated Hospital of Wenzhou Medical University from May 2016 to May 2021. A total of 207 volunteers were included, comprising 98 males with an age of (40.68±13.87) years and 109 females with an age of (42.64±14.45) years. On the lateral X-ray film, a line (L) parallel to the posterior margin of the odontoid process was drawn at the posterior edge of the lower articular surface of the axis (a), intersecting the atlas at points b, c, and d. The line segments ab, bd, bc, and the C1-C2 angle were measured, and the ratios of bd/ab and bc/ab were calculated. The ability of bd/ab and bc/ab to predict the unreasonable fixed angle of the atlantoaxial joint (≥22°) was analyzed by receiver operating characteristic (ROC) curve analysis in both male and female. The areas under the ROC curves (AUC) were calculated, and the performance of the two prediction methods was compared using the Delong's test. The cutoff value for distinguishing the unreasonableness of the C1-C2 angle and the sensitivity and specificity were calculated. Results: The ROC curve analysis in the male group showed that the AUC of bc/ab for predicting the unreasonable C1-C2 angle was 0.791 (95%CI: 0.696-0.867, P<0.001), with a cutoff value of 0.449, sensitivity of 97.3%, and specificity of 70.0%. The performance was significantly better than that of bd/ab (cutoff value 1.100, AUC=0.532, 95%CI: 0.428-0.634, sensitivity 26.3%, specificity 83.3%, P<0.001). The ROC curve analysis in the female group showed that the AUC of bc/ab for predicting the unreasonable C1-C2 angle was 0.804 (95%CI: 0.745-0.852, P<0.001), with a cutoff value of 0.488, sensitivity of 90.5%, and specificity of 58.6%. The performance was significantly better than that of bd/ab (cutoff value 0.960, AUC=0.687, 95%CI: 0.624-0.748, sensitivity 90.5%, specificity 44.8%, P=0.041). Conclusions: The bc/ab value can be used as an effective indicator to predict the unreasonable C1-C2 angle in posterior atlantoaxial fusion surgery with high diagnostic accuracy. The cutoff value for males is<0.449, and for females is<0.488.

Vertebral Artery Dissection in the Setting of Unstable Os Odontoideum: A Case Report.

CASE: A healthy 5-year-old boy presented with a gradual onset of headaches and acute global right-sided weakness over 10 days. The work-up revealed unstable os odontoideum leading to multiple posterior circulation infarcts with vertebral artery dissection. He underwent antiplatelet therapy, cervical collar immobilization, and delayed occiput to C2 posterior spinal fusion and instrumentation with iliac crest autograft. At 2-year follow-up, the patient had a solid fusion mass, appropriate cervical alignment, and was without neurologic sequelae. CONCLUSION: This case adds to a sparse body of literature in the management of vertebral artery dissection with vertebrobasilar insufficiency secondary to unstable os odontoideum.

The assessment of atlantoaxial joint involvement in patients with rheumatoid arthritis, results from an observational "real-life" study.

Atlantoaxial joint is a possible affected site during rheumatoid arthritis (RA) and, in this work, we evaluated its occurrence and associated characteristics in a "real-life" cohort. By a medical records review study of RA patients longitudinally followed-up, the occurrence of severe atlantoaxial joint involvement was estimated (incidence proportion and incidence rate per 1000 person-years at risk). Regression analyses were also exploited to evaluate possible associated factors. Based on these findings, a prospective recruitment was performed to build a descriptive cross-sectional study in evaluating a subclinical atlantoaxial joint involvement in patients with the same clinical characteristics. Retrospectively, 717 patients (female 56.6%, age 64.7 ± 12.3 years) were studied. The incidence proportion of severe atlantoaxial joint involvement was 2.1% [1.5-2.5], occurring in 15 out of 717 patients, and identified by both MRI and CT scan. Considering over 3091 person-years, an incidence rate of 5.2 × 1000 [2.9-8.3] person-years was estimated. Regression analyses suggested that male gender, a longer disease duration, ACPA positivity and extra-articular manifestations resulted to be significantly associated with a severe atlantoaxial joint involvement. Given these findings, 30 asymptomatic patients were selected according to these clinical characteristics and underwent MRI of cervical spine. To date, almost 50% of these asymptomatic patients showed a subclinical atlantoaxial joint involvement. The occurrence of the severe atlantoaxial joint involvement in RA patients was estimated in a "real-life" setting. Male gender, ACPA positivity, long disease duration, and extra-articular manifestations could be associated with the severe atlantoaxial joint involvement in RA. MRI could provide a useful clinical tool to early evaluate the atlantoaxial joint involvement in RA, also in asymptomatic patients.

Biomechanical evaluation of a novel atlas polyaxial transverse connecting screw system, an in vitro human cadaveric study.

PURPOSE: To introduce a novel transverse connecting screw system, and to evaluate the biomechanical stability of the novel screw system using human cadaveric specimens. METHODS: Six fresh-frozen cadaveric upper cervical spines were used in our study. Every specimen was tested under 5 conditions: intact group; unstable group; C1 to C2 screw rod system group; C1 to C2 + crosslink system group; atlas polyaxial transverse connecting screw (APTCS) system. RESULTS: Compared with the intact state, C1 to C2 screw rod system, C1 to C2 + CL system and APTCS showed statistically decrease range of motion in all directions except for the unstable group under posterior extension direction (P < .05). APTCS group has the least range of motion in all directions (P < .001). CONCLUSION: The APTCS system was able to restore stability to the atlantoaxial joint. APTCS system has the advantages of easy installation, convenient bone grafting, and strong biomechanical strength.