[A quantitative study of mechanics in the treatment of atlantoaxial joint disorder by tendon relaxation manipulation].

OBJECTIVE: To explore dose-effect relationship of biomechanical parameters in treating atlantoaxial joint disorder by slimming manipulation. METHODS: From October 2022 to May 2023, 18 patients with atlantoaxial joint disorders were treated, including 10 males and 8 females;aged from 24 to 27 years old with an average of (25.50±1.10) years old;CT of cervical vertebra showed 16 patients with right side distortion and 2 patients with left side distortion. The mechanical parameters of treatment of atlantoaxial joint disorder by tendon relaxation manipulation were measured by wearing massage manipulation gloves. The magnitude, frequency and mechanical curve of force during tendon relaxation and starting force, pulling force, pulling time and mechanical curve during rehabilitation were quantified, the differences between the affected and contralateral manipulations were compared. RESULTS: The maximum force and frequency of Fengchi(GB20) on the affected side were (19.82±2.02) N and (116.83±14.49) times/min, and opposite side were (13.87±2.19) N and (188.89±16.03) times/min, respectively. There were statistically difference in the maximum force and frequency of both sides (P<0.05). The maximum force and frequency of Quepen (ST12) on the affected side were (14.44±3.27) N and (139.06±28.47) times/min, and those on the opposite side were (9.41±1.38) N and (142.50±28.47) times/min. There was difference in maximum force on both sides (P<0.05). The starting force, turning force and turning time of the affected side were (14.16±5.98) N, (11.56±6.63) N, (0.14±0.03) S, and the contralateral side were (8.94±3.39) N, (8.30±4.64) N, (0.18±0.04) S, respectively. The difference of starting force, turning force and turning time on both sides were statistically significant (P<0.05). CONCLUSION: By applying a light relaxation force on the affected side, the mechanical balance between cervical vertebrae could be restored, and recovery trend of atlantoaxial joint disorder could be strengthened. On this basis, the atlantoaxial odontoid process could be reversed by applying a light rotation force, which reflects the characteristics of high safety of the manipulation.

The effect of suboccipital muscle dysfunction on the biomechanics of the upper cervical spine: a study based on finite element analysis.

OBJECTIVE: Muscle dysfunction caused by repetitive work or strain in the neck region can interfere muscle responses. Muscle dysfunction can be an important factor in causing cervical spondylosis. However, there has been no research on how the biomechanical properties of the upper cervical spine change when the suboccipital muscle group experiences dysfunction. The objective of this study was to investigate the biomechanical evidence for cervical spondylosis by utilizing the finite element (FE) approach, thus and to provide guidance for clinicians performing acupoint therapy. METHODS: By varying the elastic modulus of the suboccipital muscle, the four FE models of C0-C3 motion segments were reconstructed under the conditions of normal muscle function and muscle dysfunction. For the two normal condition FE models, the elastic modulus for suboccipital muscles on both sides of the C0-C3 motion segments was equal and within the normal range In one muscle dysfunction FE model, the elastic modulus on both sides was equal and greater than 37 kPa, which represented muscle hypertonia; in the other, the elastic modulus of the left and right suboccipital muscles was different, indicating muscle imbalance. The biomechanical behavior of the lateral atlantoaxial joint (LAAJ), atlanto-odontoid joint (ADJ), and intervertebral disc (IVD) was analyzed by simulations, which were carried out under the six loadings of flexion, extension, left and right lateral bending, left and right axial rotation. RESULTS: Under flexion, the maximum stress in LAAJ with muscle imbalance was higher than that with normal muscle and hypertonia, while the maximum stress in IVD in the hypertonic model was higher than that in the normal and imbalance models. The maximum stress in ADJ was the largest under extension among all loadings for all models. Muscle imbalance and hypertonia did not cause overstress and stress distribution abnormalities in ADJ. CONCLUSION: Muscle dysfunction increases the stress in LAAJ and in IVD, but it does not affect ADJ.

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

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

Comparison of cross-sectional area and fat infiltration of suboccipital muscles between normal dogs and dogs with atlantoaxial instability.

BACKGROUND: Atlantoaxial instability (AAI) is primarily a congenital neurological disorder affecting young toy-breed dogs. So far, most studies have focused on bones and ligaments related to AAI, and there are no studies on the suboccipital muscles (SOMs) that occupy a large area from the occipital bone to C2 in dogs. This study evaluated the cross-sectional area (CSA) and fat infiltration of the SOMs using magnetic resonance imaging (MRI), specifically, T1-weighted images, in normal dogs (≤ 5 kg) and AAI dogs. The relationship between the severity of the neurological symptoms of AAI (group A and group B) and the values from MRI was also assessed. RESULTS: AAI dogs had significantly smaller CSA (P = 0.029) and greater fat infiltration (P = 0.044) of the SOMs compared to normal dogs. AAI dogs with mild neurological symptoms for a long period (group A) had greater fat infiltration than AAI dogs with severe neurological symptoms (group B) (P = 0.035). CONCLUSIONS: The muscle changes are most likely due to spinal cord compression resulting from instability; however, the possibility that chronic changes of the muscle may play an additional role in maintaining stability in this region cannot be excluded. This study provides fundamental quantitative information of the SOMs in normal and AAI dogs.

Biomechanical evaluation of the craniovertebral junction after odontoidectomy with anterior C1 arch preservation: A finite element study.

OBJECTIVE: Odontoidectomy with preservation of the anterior C1 arch can be increasingly achieved by an endoscopic endonasal approach. It is controversial whether preservation of the anterior C1 arch after odontoidectomy can prevent instability of the craniovertebral junction （CVJ） and avoid posterior fixation. The aim of this research was to investigate the biomechanical effect of the preserved anterior C1 arch after odontoidectomy. METHODS: A validated finite element model of a whole cervical spine (occipital bone to T1) was constructed to study the biomechanical changes due to traditional odontoidectomy (TO) and odontoidectomy with preservation of the anterior C1 arch (OPC1). RESULTS: The greatest biomechanical changes in the cervical spine model after TO and OPC1 occurred at C0-C1 and C1-C2. At C0-C1 and C1-C2, the motion changes of the TO and OPC1 models had no significant difference in flexion, extension and lateral bending. Compared with the intact model, motion increases of the two surgical models were both extremely significant at C1-C2 in extension (128.2% vs. 128.1%) and lateral bending (178% vs. 156%). In axial rotation, the TO approach produced more motions than the OPC1 approach, especially at C1-C2(90.3° under TO approach, and 74.6° under OPC1 approach). CONCLUSIONS: Preservation of the anterior C1 arch after odontoidectomy can preserve the axial rotational motion at C0-C1 and C1-C2, whereas the motions in extension and lateral bending continue to have an extremely abnormal increase at C1-C2. Thus, instability of the CVJ still exists, and posterior internal fixation may also be required after OPC1.

Cervical Myeloradiculopathy and Atlantoaxial Instability in Cervical Dystonia.

OBJECTIVE: Atlantoaxial instability, although rarely reported in the literature, can be associated with cervical dystonia (CD) and may lead to compression of the cord at the craniovertebral junction. We present a case series of 4 patients of longstanding CD with neurologic complications. Treatment strategies and challenges are discussed. METHODS: Retrospective analysis of 4 cases of longstanding CD with complications of myelopathy or radiculopathy. RESULTS: The average age at onset of complications was 28 years (range, 17-37). The average duration of CD was 23.75 years. Narrowing of the craniovertebral junction was seen in 3 patients, of which 2 had os odontoideum, and 1 had rotational malalignment at the atlantoaxial joint. One patient had disc desiccation with bulge and intramedullary signal changes in the cord at C3-4 level. Medical treatment was not satisfactory, but botulinum toxin was partly useful in all. One patient had sequelae of myelopathy and did recover partially after deep brain stimulation. Of the 2 patients who underwent surgical fixation with a fusion of the spine, one improved, and the other had no improvement due to irreversible cord damage. The overall outcome was satisfactory only in 2 patients. CONCLUSIONS: Early-onset CD can lead to cord complications at a young age and at higher levels of the cervical spine and at the cervicovertebral junction. Comprehensive management by a multidisciplinary team is crucial to prevent complications early.

Revisiting bronchoscopic intratumoral chemotherapy in malignant central airway obstruction via EUS-B approach and its review of literature.

Critical central airway obstruction has always been a dreaded complication to which interventional pulmonologist commonly encounters. There have been various modalities which are used for the management and palliation, which includes mechanical coring, laser, cryoextraction, electrocautery and airway stenting. Rigid bronchoscopy with or without jet ventilation has been corner stone of therapeutics and palliation of central airway obstruction. There are only a few conditions where it is not possible to use rigid bronchoscopy. Here we report a case of metastatic tracheal tumour which presented with critical airway obstruction in a patient who had atlantoaxial instability (AAI) due to rheumatoid arthritis. Here we used endobronchial ultrasound scope (EBUS) via esophageal route, i.e. EUS-B guided approach for sampling of the tracheal tumour, and intratumoral chemotherapy was instilled in multiple sessions, which resulted in shrinking of tumour, thus relieving the critical airway obstruction. This is the first report of using EUS-B approach for intratumoral chemotherapy for tracheal tumors. Bronchoscopic intratumoral chemotherapy therapy (BITC) in tracheal tumors is also one of the options but has not been explored much and there has been a dearth of literature for it.

Compresión medular por inestabilidad atlantoaxoidea en artritis reumatoide / Medullar compression due to an atlantoaxial instability in rheumatoid arthritis

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Biomechanical study of C1 posterior arch crossing screw and C2 lamina screw fixations for atlantoaxial joint instability.

BACKGROUND: The biomechanics of C1 posterior arch screw and C2 vertebral lamina screw techniques has not been well studied, and the biomechanical performance of the constructs cannot be explained only by cadaver testing. METHODS: From computed tomography images, a nonlinear intact three-dimensional C1-2 finite element model was developed and validated. And on this basis, models for the odontoid fractures and the three posterior internal fixation techniques were developed. The range of motion (ROM) and stress distribution of the implants were analyzed and compared under flexion, extension, lateral bending, and axial rotation. RESULTS: All three kinds of fixation techniques completely restricted the range of motion (ROM) at the C1-2 operative level. The C1-2 pedicle screw fixation technique showed lower and stable stress peak on implants. The C1 posterior arch screw + C2 pedicle screw and C1 pedicle screw + C2 lamina screw fixation techniques showed higher stress peaks on implants in extension, lateral bending, and axial rotation. CONCLUSIONS: As asymmetrical fixations, C1 posterior arch screw + C2 pedicle screw and C1 pedicle screw + C2 lamina screw fixations may offer better stability in lateral bending and axial rotation, but symmetrical fixation C1-2 pedicle screw can put the implants in a position of mechanical advantage.

Occipitocervical fusion complicated with cerebellar abscess: a case report.

BACKGROUND: Occipitocervical (OC) fusion is indicated for OC instability and other conditions. Surgical complications include infection, malunion, and instrument failure. CASE PRESENTATION: We described a patient who underwent OC fusion and subsequently developed complication of cerebellar abscess and obstructive hydrocephalus. A 63-year-old male patient had been suffering from long-term neck pain and limb numbness and weakness. Cervical spine examination revealed tight stenosis at C1 level and instability in the C1-C2 joints. A C1 laminectomy with OC fusion was performed, and the patient was discharged. Unfortunately, a few days later, he went to the emergency department and complained of persistent dizziness, vomiting, and unsteady gait. Computed tomography (CT) and magnetic resonance imaging (MRI) images revealed a suspicious cerebellar abscess formation and hydrocephalus. Furthermore, CT images indicated that the left screw was loose, and the diameter of the right screw hole was much larger than the size of the screw. Besides, inappropriate length of the screw penetrated the occipital bone and may cause the disruption of dura mater. The patient underwent external ventricular drainage first, followed by abscess drainage and C1-C2 fixation a few days later. He was discharged without any further neurological deficits or infectious problems. The patient recovered with intact consciousness, full muscle strength, and improved numbness throughout the extremities, with a Nurick grade of 1. A follow-up magnetic resonance imaging at 3 months after surgery revealed near total resolution of the abscess. Inform consent was obtained from this patient. CONCLUSIONS: Carefully conducting the procedure using the most tailored approach is essential to successful surgery, but this rare complication should always be kept in mind.

Grisel Syndrome: Case Report

We report a case of a rare disease, Grisel syndrome, which manifests as a kind of rotational fixation of the atlas on the axis, resulting from an infectious process of the upper airways. In the present report, we discuss etiology, clinical presentation, diagnosis, treatment and outcome after intervention.

An Updated Algorithm for Radiographic Screening of Upper Cervical Instability in Patients With Down Syndrome.

STUDY DESIGN: Retrospective evaluation of cervical spine images from 2006-2012 for the purposes of "screening" children with Down syndrome for instability. OBJECTIVE: To determine whether a full series of cervical spine images including flexion/extension lateral (FEL) radiographs was needed to avoid missing upper cervical instability. SUMMARY OF BACKGROUND DATA: The best algorithm, measurements, and criteria for screening children with Down syndrome for upper cervical instability are controversial. Many authors have recommended obtaining flexion and extension views. We noted that patients who require surgical stabilization due to myelopathy or cord compression typically have grossly abnormal radiographic measurements on the neutral upright lateral (NUL) cervical spine radiograph. METHODS: The atlanto-dental interval, space available for cord, and basion axial interval were measured on all films. The Weisel-Rothman measurement was made in the FEL series. Clinical outcome of those with abnormal measurements were reviewed. Sensitivity, specificity, and positive and negative predictive values of NUL and FEL radiographs for identifying clinically significant cervical spine instability were calculated. RESULTS: A total of 240 cervical spine series in 213 patients with Down syndrome between the ages of 4 months and 25 years were reviewed. One hundred seventy-two children had an NUL view, and 88 of these patients also had FEL views. Only one of 88 patients was found to have an abnormal atlanto-dental interval (≥6 mm), space available for cord at C1 (≤14 mm), or basion axial interval (>12 mm) on an FEL series that did not have an abnormal measurement on the NUL radiograph. This patient had no evidence of cord compression or myelopathy. CONCLUSIONS: Obtaining a single NUL radiograph is an efficient method for radiographic screening of cervical spine instability. Further evaluation may be required if abnormal measurements are identified on the NUL radiograph. We also propose new "normal" values for the common radiographic measurements used in assessing risk of cervical spine instability in patients with Down syndrome. LEVEL OF EVIDENCE: Level IV.

Surgical Fixation Using Screw-Rod Construct Instrumentation for Upper Cervical Instability in Pediatric Down Syndrome Patients.

STUDY DESIGN: Retrospective case series. OBJECTIVES: To describe the indications and outcomes of cervical fixation using modern instrumentation in a case series of pediatric Down syndrome (DS) patients. SUMMARY OF BACKGROUND DATA: Cervical instability is the major cervical spine concern in children with DS. Although fixation techniques have advanced over the past quarter-century, the outcome of fixation with modern instrumentation for upper cervical instability in DS patients has not been thoroughly investigated. METHODS: We searched the orthopedic database at our institution for patients with a diagnosis of DS who had undergone a cervical spine fusion between 2006 and 2017. Patient demographics, diagnoses, surgical indications, surgical details, and complications were recorded. Preoperative imaging was reviewed to determine atlanto-dens intervals and spinal cord signal changes. Postoperative radiographs or CT scans were reviewed to determine union. RESULTS: Twelve DS patients met our inclusion criteria. The mean age at surgery was 9.3 years (range 3.8-18.8 years). Patients with secondary causes of instability included 7 patients with os odontoideum and 1 patient with a pars fracture. Three patients (25%) were identified on asymptomatic screening, with none of these having cord signal changes on magnetic resonance imaging (MRI). Modern implants (screws, plates, cages) were used in every patient in our series. The mean number of levels fused was 1.9 (range 1-5). The overall complication rate was 41.7% (5/12). Four patients required repeat surgery for nonunion. All patients with adequate radiographic follow-up demonstrated union (11/11, 100%). One patient was lost to follow-up. CONCLUSIONS: Fixation for cervical instability is a critical component of the management of DS. A minority of patients receiving surgery were identified through asymptomatic screening. There was a high complication risk associated with surgery in our study; however, the addition of rigid fixation has lessened the complication rate compared with previous studies. LEVEL OF EVIDENCE: Level IV.

Anatomic Considerations for Injection of the Lateral Atlanto-Axial Joint.

OBJECTIVE: We aimed to define the potential complications of intra-articular steroid injections into the lateral C1-2 articulations and safety margins to the relevant structures. METHODS: A total of 488 contrast-enhanced computed tomography angiogram (CTA) "arch to vertex" studies were retrospectively reviewed for theoretical intersection of the vertebral artery or thecal sac and distance of the named structures from the anticipated/theoretical trajectory of injection into the lateral C1-C2 joint. RESULTS: Patients were 60.4±15.8 years old and 55.5% male. In total, seven vertebral arteries and 11 thecal sac theoretical intersections were found. In cases without a direct intersection, the distance from the trajectory (range) was 0.71±0.18 (0.22-1.44) cm to the vertebral artery and 0.6±0.22 (0.14-1.8) cm to the thecal sac. CONCLUSIONS: Although injection of steroid into the lateral C1-C2 articulation for pain management has historically been reported to carry risk of severe complications due to close proximity and location variability of surrounding structures, our study quantifies the potential risk of such injections. Further, our analysis suggests that preprocedural imaging should be considered.

Traumatic Atlantoaxial and Fracture-Related Dislocation.

Traumatic atlantoaxial dislocation due to ligamentous and combined osseous injuries rarely occurs in adults. There are only few cases published in the literature. In this level 4 study, a cohort of nine consecutive patients suffering from traumatic atlantoaxial dislocation has been analyzed regarding morphology of injury, trauma mechanism, and outcome since 2007. Three types of those injuries have been found regarding direction of dislocation indicating the underlying ligamentous injuries as well as the accompanying grade of instability. Firstly, there was rotatory dislocation, if the alar ligaments were injured. Secondly, there occurred horizontal dislocation, when transverse atlantal ligament was damaged additionally. Thirdly, excessive ligamentous injury led to distraction of the atlantoaxial complex resulting in dissociation of the atlas against the axis. Additionally fractures of the atlas as well as of the odontoid process (type II or III according to Anderson/D'Alonzo) were diagnosed frequently. Atlantoaxial dislocation injuries, especially distraction injuries, offer a high risk for accompanied neurovascular disorders deserving reduction followed by surgical fixation. Only rotatory injuries leading to ligamentous damage solitarily can safely be successfully treated conservatively. Understanding of the injuries' morphology is essential, in order to set the correct diagnosis and to implicate the most advantageous treatment regime.

Atlantoaxial Instability Resulting in Intractable Nausea in a Person with C5 Complete Spinal Cord Injury: A Case Report.

Individuals with spinal cord injury (SCI) have altered neurophysiology and present with symptoms that must be interpreted in the context of their specific neurologic injury. This is a case of a 16-year-old female adolescent with C5 American Spinal Injury Association Impairment Scale A SCI who presented with intractable nausea. Multiple etiologies for her nausea, including medication effect, metabolic and gastrointestinal disorders, autonomic dysreflexia, and mood disorder, were systematically ruled out. Due to the persistence of the patient's symptoms and suboptimal progression in her rehabilitation, a central nervous system etiology was investigated. Ultimately, atlantoaxial instability with odontoid compression on the medulla was identified and her refractory nausea resolved following an occiput to C2 fusion. To our knowledge, this is the first reported case of atlantoaxial instability causing intractable nausea due to brain stem compression in a patient with SCI. Level of Evidence: V.

The Craniovertebral Junction in Rheumatoid Arthritis: State of the Art.

Rheumatoid arthritis (RA) is a chronic inflammatory disorder, characterized by polyarticular inflammation causing progressive joint damage and disability. The mechanisms underlying its pathogenesis involve activation of innate and adaptive immunity, microvascular endothelial cell activation, and inflammatory infiltration of lymphocytes and monocytes into the synovium. Spinal involvement in RA is not typical; when it occurs, the main radiological features are (1) atlantoaxial subluxation (AAS), which is the most typical form of cervical spine involvement; (2) cranial settling-also known as basilar impression, atlantoaxial impaction or superior migration of the odontoid-which is the most severe form of associated spinal instability; and (3) subaxial subluxation. A combination of these alterations may occur. Synovitis is characterized by infiltration of innate and adaptive immune cells; joint destruction is a consequence of activation of synovial fibroblasts, which acquire aggressive, inflammatory, invasive features, associated with increased chondrocyte catabolism and synovial osteoclastogenesis.Neck pain is the most frequent symptom of spinal involvement in RA; it occurs in 40-80% of patients and is mostly localized at the craniocervical junction. Other symptoms-caused by compression of neural structures such as the greater occipital nerve (at C2), the nucleus of the spinal trigeminal tract and the greater auricular nerve-are occipital neuralgia, facial pain and ear pain, respectively. Irritation of the lesser occipital nerve (at C1) can cause pain in the suboccipital region. Sometimes patients may complain of a sensation of their head falling down with flexion, weakness, reduced endurance, loss of ability, gait alterations, paraesthesias or other symptoms due to cord and medullary compression, and upper or lower motor neuron signs, or both. Surgical management of RA remains a challenging field.

Ossification of the Posterior Longitudinal Ligament: Analysis of the Role of Craniovertebral and Spinal Instability.

BACKGROUND: This paper reviews an experience of surgically treating ossification of the posterior longitudinal ligament (OPLL) with fixation of the involved spinal segments alone, without resorting to any bony or soft tissue decompression or attempts at direct resection of the OPLL. While in the early part of the experience, stabilization of only the involved subaxial cervical spinal segments was done, in the later part of the experience, atlantoaxial fixation was included in the multisegmental spinal fixation construct. This treatment is based on the understanding that spinal instability that includes atlantoaxial instability forms the nodal point of the pathogenesis and development of OPLL, and maturation of the presenting clinical symptoms. MATERIALS AND METHODS: Twenty-nine patients were treated in this series. There were 28 males and one female, and their ages ranged from 28 to 75 years (average 57 years). All patients presented with symptoms of neck pain, and progressive and disabling myelopathy-related quadriparesis. In the early part of the series (from 2012 to 2014), 14 patients underwent multilevel subaxial cervical spinal fixation by a transarticular technique of facetal fixation. After November 2014, atlantoaxial lateral mass fixation was included in the fixation construct in the subsequent 15 patients. Clinical assessments were done using a visual analogue scale (VAS), the Japanese Orthopaedic Association (JOA) scale and Goel's clinical grading scale. RESULTS: All patients' clinical symptoms improved in the immediate postoperative period, and the improvement was sustained and progressive in 28 patients. CONCLUSION: Atlantoaxial and subaxial spinal instability seems to be the nodal pathogenetic factor in OPLL. Only stabilization of spinal segments that includes the atlantoaxial joint can provide a safe, simple and rational form of treatment.