Physiotherapeutic Approach Towards Sensory and Motor Recovery in a Patient With Lateral Mass Fixation: A Report of a Rare Case.

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

Subluxación atlantoaxial en artritis reumatoidea. Resolución por odontoidectomía endonasal endoscópica y fusión e instrumentación por abordaje posterior. Reporte de caso

La subluxación atlantoaxial es la lesión más frecuente en la columna cervical causada por la artritis reumatoidea. Se manifiesta por rigidez de nuca, dolor cervical y déficit neurológico. El diagnóstico se realiza con tomografía computarizada e imágenes de resonancia magnética. El intervalo atlanto dental anterior mayor a 5mm indica inestabilidad atlantoaxial, el intervalo atlanto dental posterior menor a 14mm advierte riesgo neurológico. Las indicaciones más frecuentes de cirugía son: dolor cervical severo, inestabilidad y síntomas de mielopatía. Cuando existe compresión medular es necesaria la descompresión cervical alta sea por vía posterior o por vía anterior (odontoidectomía endonasal versus transoral). La línea rinopalatina nos indicará la factibilidad de una odontoidectomía endonasal endoscópica (OEE). El objetivo de la presentación del presente caso es compartir nuestra experiencia con la primera odontoidectomía endonasal endoscópica realizada en nuestro país y fomentar la utilización de la técnica. La cirugía fue realizada en un paciente con cuadriparesia espástica por subluxación atlantoaxial por artritis reumatoidea y que presentó excelente evolución pos operatoria, con recuperación casi completa. La OEE es una técnica operatoria mínimamente invasiva, ideal para pacientes con múltiples comorbilidades y que ofrece de buenos a excelentes resultados.

Atlantoaxial subluxation is the most common injury to the cervical spine caused by rheumatoid arthritis. It is manifested by neck stiffness, neck pain and neurological deficit. Diagnosis is made with computed tomography and magnetic resonance imaging. The anterior dental atlanto interval greater than 5mm indicates atlantoaxial instability, the posterior dental atlanto interval less than 14mm warns of neurological risk. The most frequent indications for surgery are: severe neck pain, instability and symptoms of myelopathy. When there is spinal cord compression, upper cervical decompression is necessary, either via a posterior or anterior approach (endonasal versus transoral odontoidectomy). The rhinopalatine line will indicate the feasibility of an endoscopic endonasal odontoidectomy (EEO). The objective of the presentation of this case is to share our experience with the first endoscopic endonasal odontoidectomy performed in our country and to promote the use of the technique. The surgery was performed on a patient with spastic quadriparesis due to atlantoaxial subluxation due to rheumatoid arthritis and who presented excellent postoperative evolution, with almost complete recovery. EEO is a minimally invasive surgical technique, ideal for patients with multiple comorbidities and offering good to excellent results.

Multimodal Management of Coexisting Atlantoaxial Subluxation and Spinal Stenosis in an Older Adult: A Case Report and Literature Review.

This case report investigates the diagnostic and therapeutic challenges caused by the coexistence of atlantoaxial subluxation and spinal stenosis in a 70-year-old male patient with chronic progressive numbness in both hands. A detailed assessment showed that the patient's symptoms were primarily caused by spinal stenosis, not atlantoaxial subluxation. Considering the patient's age and preference for nonsurgical treatment, a conservative chiropractic care plan was implemented, significantly improving his symptoms and quality of life. This case highlights the potential benefit of conservative chiropractic care in managing such complex cases, emphasizes the need for meticulous diagnosis, and requires further research to validate these findings and develop comprehensive management guidelines.

Prevalence of anterior atlantoaxial subluxation and association with established rheumatoid arthritis.

OBJECTIVE: Spinal involvement in rheumatoid arthritis (RA) is limited to the upper cervical spine, leading to cervical spine instability. This study aimed to evaluate the prevalence of anterior atlantoaxial subluxation (aAAS) and its associated risk factors in patients with RA. METHOD: This single-centre cross-sectional study 240 patients consecutively were recruited. Radiographs of the cervical spine were obtained in the flexion and neutral neck positions and read by two blinded observers. The diagnosis of aAAS was based on the distance between the anterior aspect of the dens and the posterior aspect of the anterior arch of the atlas, which was >3 mm during flexion. Statistical analysis was performed to determine the predictive factors of aAAS. RESULTS: Two hundred and forty patients with a mean ± SD age of 56.4 ± 11.4 years were recruited, and 191 (78%) were female. The mean ± SD duration of the disease was 10.2 ± 8.5 years. Of all 25 cases (10.4%) diagnosed with aAAS, the mean anterior atlantodental interval in patients with AAS was 4.19 ± 1.20 mm. One in three patients with aAAS had no neck pain. Patients with aAAS had longer disease duration, lower age at diagnosis, lower body mass index, higher anti-cyclic citrullinated peptide autoantibodies (anti-CCP), more frequent erosion, joint restriction, and joint prostheses. In the multivariate regression model, joint limitation, history of joint prostheses, low BMI, and higher anti-CCP levels were independent predictors of the aAAS. CONCLUSION: Thirty-three percent of patients with cervical involvement do not experience neck pain. Cervical involvement should be considered even without neck pain, particularly in established diseases.

Retrospective analysis of atlantoaxial rotatory fixation describing age distribution and gender ratio in children and adolescents: A preliminary report.

INTRODUCTION: Atlantoaxial rotatory fixation (AARF) in children presents with an acute onset of neck pain. Almost all cases heal within a few days of onset and are treated conservatively. Because few cases of AARF have been reported, the age distribution or gender ratio of AARF in the child population have not been described enough. In Japan, the social insurance system covers all citizens. Thus, we used insurance claims data to investigate the features of AARF. The aim of this study is to examine the age distribution, compare gender ratio and determine the recurrence proportion of AARF. METHODS: We used the JMDC database to search for claims data submitted between January 2005 and June 2017 for cases of AARF in patients aged <20 years. RESULTS: We identified 1949 patients with AARF, of which 1102 (56.5%) were male. The mean age was 98.3 ± 42.2 months and 91.6 ± 38.4 months in males and females, respectively, and males with AARF were significantly older at onset than females with AARF (p < 0.001). In both sexes, the highest frequency of AARF occurred when the patient was 6 years old. There were 121 (6.2%) cases of recurrent AARF (male: 61, 5.5%; female: 60, 7.1%), but the age differences between the sexes in these cases were not statistically significant. CONCLUSIONS: This is the first report to describe the characteristics of the study population of AARF. Males were more likely to suffer from AARF than females. Furthermore, age (in months) at AARF onset was significantly higher in males than in females. Recurrence rate was not significant in both sexes.

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.

Atlantoaxial Subluxation in a 10-Year-Old Girl With Down Syndrome: A Case Report.

Down syndrome is the most common inherited chromosomal disorder caused by trisomy 21. Atlantoaxial instability (AAI) is more common in children with Down syndrome, resulting from ligament laxity and odontoid dysplasia. We report the case of a 10-year-old girl with Down syndrome submental. She came to the ER with a history of abnormal gait for one week and was admitted with a case of ataxia for investigations. Moreover, we discovered that she had atlantoaxial subluxation, which was treated surgically.

Automatic evaluation of atlantoaxial subluxation in rheumatoid arthritis by a deep learning model.

BACKGROUND: This work aims to develop a deep learning model, assessing atlantoaxial subluxation (AAS) in rheumatoid arthritis (RA), which can often be ambiguous in clinical practice. METHODS: We collected 4691 X-ray images of the cervical spine of the 906 patients with RA. Among these images, 3480 were used for training the deep learning model, 803 were used for validating the model during the training process, and the remaining 408 were used for testing the performance of the trained model. The two-dimensional key points' detection model of Deep High-Resolution Representation Learning for Human Pose Estimation was adopted as the base convolutional neural network model. The model inferred four coordinates to calculate the atlantodental interval (ADI) and space available for the spinal cord (SAC). Finally, these values were compared with those by clinicians to evaluate the performance of the model. RESULTS: Among the 408 cervical images for testing the performance, the trained model correctly identified the four coordinates in 99.5% of the dataset. The values of ADI and SAC were positively correlated among the model and two clinicians. The sensitivity of AAS diagnosis with ADI or SAC by the model was 0.86 and 0.97 respectively. The specificity of that was 0.57 and 0.5 respectively. CONCLUSIONS: We present the development of a deep learning model for the evaluation of cervical lesions of patients with RA. The model was demonstrably shown to be useful for quantitative evaluation.

C1-C2 subluxation in enthesitis-related arthritis: two case reports and literature review of ten cases.

BACKGROUND: C1-C2 subluxation is a rare complication of enthesitis-related arthritis (ERA). If left untreated, it may lead to functional impairment or cervical spinal cord compression. This study aims to highlight key points regarding the management of C1-C2 subluxation in ERA. CASE PRESENTATION: We present two cases of C1-C2 subluxation: an 8-year-old boy with ERA and 16-year-old boy with ERA with bilateral sacroiliitis. Ten cases of ERA in the literature were reviewed. The diagnosis of C1-C2 subluxation is mostly based on radiographs and cervical spine computed tomography. All patients were treated with non-steroidal anti-inflammatory drugs. Six ERA patients were treated surgically for cervical fusion. Most ERA patients with sacroiliitis had cervical collar protection. Neurologic abnormalities after treatment were not reported. Despite the use of cervical collar, cervical fusion and persisting ankylosis were found in two ERA patients with sacroiliitis without surgical treatment. CONCLUSIONS: Cervical spine protection and ruling out spinal cord compression should be prioritized, in addition to controlling the underlying inflammation in ERA. Cervical halter traction may be applied after severe cervical inflammation is excluded. To reduce the risk of complications, early recognition and appropriate treatments of C1-C2 subluxation in ERA are essential.

Atlantoaxial Instability after Treatment of Atlantoaxial Rotatory Fixation: A Case Report.

Introduction: We encountered a case of atlantoaxial subluxation (AAS) after treatment of atlantoaxial rotatory fixation (AARF). Reports of developing AAS after AARF are extremely rare. Case Report: An 8-year-old male who feels neck pain was diagnosed with AARF type II according to the Fielding classification. Computed tomography (CT) showed that the atlas was rotated 32° to the right relative to the axis. Neck collar, Glisson traction, and reduction under anesthesia were performed. Five months after the onset of AARF, the patient was diagnosed with AAS due to dilatation of atlantodental interval (ADI) and underwent posterior cervical fusion. Conclusion: AARF treatments, such as long-term Glisson traction and reduction under general anesthesia, which exert a stress on the cervical spine, may damage the alar ligaments, apical ligaments, lower longitudinal band, and Gruber's ligament. Transverse ligament damage can also occur during the treatment of AARF, especially if AARF is refractory or requires long-term treatment. In addition, knowledge of the pathophysiology of atlantoaxial instability after AARF treatment is important.

Atlantoaxial Subluxation Associated With Chronic Motor Tics.

Head jerking is one of the most common symptoms of motor tics, and because of this, patients are at an increased risk of cervical spine disorders. However, there have been no reports of atlantoaxial subluxation in the English literature. To the best of our knowledge, this is the first case of atlantoaxial subluxation associated with chronic motor tics. A 41-year-old man with a history of chronic motor tics since childhood was diagnosed with high cervical myelopathy due to atlantoaxial subluxation. The patient underwent posterior fusion surgery using atlantoaxial instrumentation and an autologous bone graft. Although screw breakage occurred as an early postoperative instrumentation failure, the clinical outcome was excellent after surgery without recurrence of subluxation. Other techniques such as atlantoaxial transarticular fixation and occipitocervical fusion followed by long-term external immobilization might be treatment options at the initial surgery, or in case of postoperative recurrent atlantoaxial subluxation.

Corrigendum: Genetically predicted C-reactive protein mediates the association between rheumatoid arthritis and atlantoaxial subluxation.

[This corrects the article DOI: 10.3389/fendo.2022.1054206.].

Predictors factors of atlanto-axial subluxation in Tunisian patients with rheumatoid arthritis.

BACKGROUND: The aim of this study was to describe clinical and imaging features of atlantoaxial subluxation (AAS) and the associated risk factors in patients with rheumatoid arthritis (RA). METHODS: We conducted a retrospective and comparative study including 51 RA patients with AAS and 51 RA patients without AAS. Atlantoaxial subluxation was defined by the presence of an anterior C1C2 diastasis on the cervical spine radiograph in hyperflexion and/or an anterior, posterior, lateral or rotatory C1C2 dislocation on MRI with/without inflammatory signal. RESULTS: In G1, clinical presentations revealing AAS were mainly neck pain (68.7%) and neck stiffness (29.8%). MRI revealed: diastasis C1C2 (92.5%), periodontoid pannus (92.5%), odontoid erosion (23.5%), vertical subluxation (9.8%) and spinal cord involvement (7.8%). A collar immobilisation and corticosteroid boluses were indicated in 86.3% and 47.1% of cases. C1-C2arthrodesis was performed in 15.4% of cases. Atlantoaxial subluxation was significantly associated with: age at disease onset (p = 0.009), history of joint surgery (p = 0.012), disease duration (p = 0.001), rheumatoid factor (p = 0.01), anti-cyclic citrullinated peptide (p = 0.02), erosive radiographic status (p < 0.005), coxitis (p < 0.001), osteoporosis (p = 0.012), extra-articular manifestations (p < 0.001), and high disease activity (p = 0.001). Multivariate analysis identified RA duration (p < 0.001, OR = 1.022 CI[1.01-1.034]) and erosive radiographic status (p = 0.01, OR = 21.236 CI[2.05-219.44]) as predictive factors of AAS. CONCLUSION: Our study showed that longer disease duration and joint destruction are the major predictive factors of AAS. Early treatment initiation, tight-control and regular monitoring of cervical spine involvement are required in these patients.

Challenges in Grisel's Syndrome Management in a Two-Month-Old Infant.

Grisel's syndrome (GS) is a rare neurosurgical condition involving nontraumatic rotatory subluxation of the atlantoaxial joint. This case report presents a two-month-old infant girl, the youngest reported case of this syndrome based on our literature review to the date of this publication. The infant was initially referred to our hospital as a case of the arachnoid cyst but was subsequently neuroradiologically diagnosed with GS, which was believed to be secondary to a retropharyngeal abscess. After developing weakness and developmental delay as well as failing conservative management for two years, the infant underwent C1 laminectomy and occipitocervical sublaminar wire fusion with favorable outcomes. GS should be considered a differential even if the patient does not present with typical signs such as torticollis and neck pain. If not identified early and treated effectively, it can result in severe neurological damage. The management plan largely depends on the Fielding-Hawkins grade of subluxation and the timing of diagnosis.

The association between Disease Activity Score and rheumatoid arthritis-associated cervical deformity: radiological evaluation of the BeSt trial.

OBJECTIVE: The authors' objective was to evaluate the association of the Disease Activity Score (DAS) with cervical spine deformity in rheumatoid arthritis (RA) patients during 10-year optimal treatment of systemic disease. METHODS: The authors evaluated radiological and 10-year follow-up (FU) data of the BeSt (BehandelStrategien) trial. In 272 RA patients, atlantoaxial subluxation (AAS), presence of vertical translocation (VT), and subaxial subluxation (SAS) were evaluated. The associations of these deformities with DAS, self-assessed health (determined with the Health Assessment Questionnaire [HAQ]), and erosions of the hands and feet (Sharp-Van der Heijde score) were studied. RESULTS: After 10 years of FU, AAS (> 2 mm neutral position) was observed in 62 patients (23%), AAS (≥ 3 mm in flexion) in 24%, AAS (≥ 5 mm in flexion) in 7%, VT did not occur, and SAS was present in 60 patients (22%). In total, 135 patients (50%) were in remission (DAS < 1.6) at 10 years of FU. No association could be established between AAS and DAS. Patients with cervical spine deformity (AAS > 2 mm and/or SAS) at 10 years had a higher HAQ score at 10 years than patients without cervical spine deformity (HAQ scores of 0.65 and 0.51, respectively, p = 0.04; 95% CI -0.29 to 0.00). CONCLUSIONS: Even though 50% of patients were in remission after 10 years and the BeSt trial was designed to optimize treatment, 40% of patients developed at least mild RA-associated cervical spine deformity and 7% developed significant AAS. This indicates that even in this era of disease-modifying antirheumatic drugs and biologicals, cervical deformity is prevalent among patients with RA and should not be neglected in patient treatment plans and information.

Application of a Modified Dorsal Wiring Method in Toy Breed Dogs With Atlantoaxial Subluxation.

BACKGROUND/AIM: Atlantoaxial subluxation (AAS) is a congenital or traumatic condition that often requires surgical stabilization. Surgery is performed via a ventral or dorsal approach. A ventral approach is challenging in toy breed dogs due to their small-sized bones. Reducing AAS by orthopedic wire via a dorsal approach can cause iatrogenic spinal cord damage. Due to these limitations, a Kishigami atlantoaxial tension band (Kishigami AATB) that remains in the epidural space has been devised. Similar to the Kishigami AATB, the present study developed a modified dorsal wiring method and evaluated it in toy breed dogs with AAS. MATERIALS AND METHODS: Medical data of toy breed dogs with AAS that underwent surgical stabilization using the modified dorsal wiring method from 2017 to 2020 were retrospectively reviewed. RESULTS: A total of 10 dogs were analyzed. Regarding the history of these dogs, six dogs had congenital AAS, and the remaining four dogs had traumatic AAS. Evaluation via computed tomography was available for five dogs, of which two dogs were identified as having incomplete ossification of their atlas. Although four dogs required a revision surgery because of recurrence of clinical signs or fracture of the atlas, final functional improvement was achieved in nine dogs. One dog showed worsened neurological status that led to death. CONCLUSION: Clinical results with the modified dorsal wiring method were similar to those with the Kishigami AATB. The modified dorsal wiring method is versatile as it could be applied to various shapes of dogs' atlas. Considering the shape of the atlas, it is recommended to apply the implant as far from the midline of the dorsal arch as possible to avoid fractures. With selection of suitable patients, this modified dorsal wiring method can be applied to dorsal stabilization of AAS in toy breed dogs.

Neck pain and related factors in patients with rheumatoid arthritis.

OBJECTIVES: In rheumatoid arthritis, neck pain can be caused by inflammatory reactions or cervical lesions, but the prevalence and associated factors have not been well studied. This study aimed to investigate the prevalence of neck pain in patients with rheumatoid arthritis and elucidate the related factors. METHODS: This study included 146 patients with rheumatoid arthritis. Neck pain, quality of life, and levels of anxiety and depression were evaluated using a questionnaire. Cervical lesions and spinal alignment were evaluated using plain radiograph and magnetic resonance imaging. Factors associated with neck pain were analysed using a logistic regression model. RESULTS: Fifty-six per cent of the patients had neck pain, and the quality of life scores were significantly worse in these patients. Multivariate analysis revealed age, C7 sagittal vertical axis, upper cervical lesion, and endplate erosion as factors associated with neck pain in patients with rheumatoid arthritis. CONCLUSIONS: More than half the patients with rheumatoid arthritis suffer from neck pain, and neck pain affects the quality of life and activities of daily living. Neck pain was associated with upper cervical lesion and endplate erosion suggesting the importance of radiological examination in patients with rheumatoid arthritis and neck pain.

Bilateral persistent intersegmental artery in a patient with posterior atlantoaxial subluxation after subaxial cervical laminoplasty.

INTRODUCTION AND IMPORTANCE: To summarize the clinical manifestations and treatment of bilateral persistent first intersegmental artery (PFIA) in a patient with posterior subluxation of atlantoaxial joint. CASE PRESENTATION: A-85-year-old woman with a two-months history of aggravating of gait disturbance and finger clumsiness was referred to our hospital. Magnetic resonance imaging revealed posterior subluxation of the atlantoaxial joint and spinal cord compression at C1 level. Three-dimensional computed tomography angiography (CTA) of cervical spine showed bilateral PFIA and left side high-riding VA. Because of the high risk of vertebral artery injury with posterior arch resection and lateral mass screw insertion due to the presence of PFIA, as well as the bony fragility of the cervical spine and the fact that the posterior atlantoaxial subluxation was reduced in the flexed position, the posterior occipito-thoracic fixation without posterior arch resection in the mildly flexed cervical position was underwent. The postoperative course was uneventful and her neurological symptoms improved gradually after surgery. CLINICAL DISCUSSION: PFIA is a very rare condition representing between 0.01 % and 1.8 %. Most patients with this condition have a unilateral persistent segmental artery, but in a small minority of cases it occurs bilaterally. It may be more difficult to resect of posterior arch or insert the C1 lateral mass screw in cases of PFIA. CONCLUSION: The best way to avoid IVAI may be careful examining the abnormal running of VA preoperatively especially on 3D-CT of cervical spine with arteriography and not to choose a technique with a high risk of VA injury.

Os odontoideum: A comprehensive review.

Os odontoideum (OO) is a rare craniocervical anomaly that is characterized by a round ossicle separated from the C2 vertebral body. With a controversial etiology and unknown prevalence in the population, OO may be asymptomatic or present in patients with myelopathic and neurological symptoms. In this literature review, we aimed to investigate epidemiology, embryology, pathophysiology, clinical presentation, and the role of diagnostic radiography in OO. By providing an overview of different management strategies, surgical complications, and postoperative considerations for OO, our findings may guide neurosurgeons in providing proper diagnosis and treatment for OO patients. A literature review was conducted using the PubMed, EMBASE, and Scopus databases. A search using the query "os odontoideum" yielded 4319 results, of which 112 articles were chosen and analyzed for insights on factors such as etiology, clinical presentation, and management of OO. The presentation of OO varies widely from asymptomatic cases to severe neurological deficits. Asymptomatic patients can be managed either conservatively or surgically, while symptomatic patients should undergo operative stabilization. Although multiple studies show different techniques for surgical management involving posterior fusion, the diversity of such cases illustrates how treatment must be tailored to the individual patient to prevent complications. Conflicting studies and the paucity of current literature on OO highlight poor comprehension of the condition. Further understanding of the natural history of OO is critical to form evidence-based guidelines for the management of OO patients. More large-center studies are thus needed to promote accurate management of OO patients with optimal outcomes.

Radiographic Evaluation of Atlas and Axis Anomalies in Toy Breed Dogs With and Without Atlantoaxial Subluxation.

BACKGROUND/AIM: Atlantoaxial subluxation (AAS) is generally a congenital condition that mainly affects toy breed dogs. Previous studies in several toy breed dogs revealed that dogs with AAS had a relatively high proportion of incomplete ossification (IO) of the atlas and dens anomalies compared to dogs without AAS. These anatomical characteristics may be important in surgical decision-making. Thus, the present study evaluated morphological differences in the atlas and axis between Maltese dogs with and without AAS. MATERIALS AND METHODS: The medical records of Maltese dogs with and without AAS from 2015 to 2020 were analyzed. Abnormalities of the atlas and axis were evaluated using computed tomography (CT). RESULTS: A total of 45 dogs were reviewed. Maltese dogs with AAS revealed a higher ratio of IO of the atlas (56%) than non-affected dogs (19%). Dens anomalies were identified in 78% of the dogs with AAS and in 26% of non-affected dogs. The shape of the atlas has been identified as thin, solid compact bone in Maltese dogs. Dogs that revealed IO of the dorsal arch of the atlas showed significantly lower CT values (in Hounsfield units) than dogs without IO. The CT values of the midline of the dorsal arch were significantly lower than those of the outer surrounding region. Dens hypoplasia was defined by measuring the dens-to-axis length ratio according to a previous study. A significantly lower ratio was identified in dogs with AAS than in non-affected dogs. CONCLUSION: The incidence ratio of abnormalities of the atlas and axis in Maltese dogs with AAS was similar to that of previous studies. The dorsal arch of the atlas is composed of thin cortical bone with a vulnerable midline region. As dogs with AAS are more likely to be afflicted with abnormalities in the atlas and axis, considering these morphological features is important when planning the surgical stabilization of AAS.