Concept of 'Central' or 'Axial' Atlantoaxial Instability

The atlantoaxial joint is the most mobile joint of the spine and is most liable to develop instability. Atlantoaxial instability can be identified on observation of facetal alignment on lateral profile imaging, telltale clinical and radiological evidence and by direct observation of instability by manual manipulation of bones during surgery. Central or axial atlantoaxial instability is when there is no abnormal increase in atlantodental interval on dynamic imaging and there is no dural or neural compression by the odontoid process. Understanding and appropriately treating central or axial atlantoaxial instability can have clinical implications.

P015 Imaging findings in cervical spine in patients with Juvenile Idiopathic Arthritis in Tunisia

Background Juvenile Idiopathic Arthritis (JIA) is a chronic disease characterized by prolonged synovial inflammation that may cause structural joint damage. However, little is known about cervical spine involvement in JIA. The main objective of this study is to describe radiological findings of the cervical spine in patients with JIA. Methods We conduct a retrospective monocentric study. All JIA patients were included (ILAR criteria). Sociodemographic, JIA subtype, and clinical characteristics were collected. Disease activity at JIA diagnosis was evaluated by JADAS10 (Juvenile Arthritis Disease Activity Score) in poly and oligoarticular subtypes and by BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) in arthritis-related enthesitis form. Cervical spine radiographs including anteroposterior and lateral with flexion views were analyzed. A p-value < 0.05 was considered significant. Results We included 25 patients (16 girls and 9 boys) diagnosed with JIA with a mean age at disease onset of 9.9 ± 3.9 [3–16]. The median disease duration was 36 months (IQR 25–75%; 30–84). The JIA subtypes were in decreasing order of frequency: Enthesitis-related Arthritis (n = 9), Oligoarticular (n = 6), Polyarticular RF- (n = 4), Polyarticular RF + (n = 2), Systemic (n = 2), Psoriatic Arthritis (n = 1), and Undifferentiated (n = 1). Median ESR and CRP were 17 mm/h [2–98] and 15.4 mg/l [0–56] respectively. The Median BASDAI score was 2.8 [1–6.3]. Median JADAS10 score was 5.3 [0–20]. Four patients (16%) were on long-term corticosteroid therapy. Five patients (20 %) have a cervical spine involvement with the following subtypes: Polyarticular (n = 2), enthesitisenthesitis-related arthritis (n = 2), and systemic (n = 1). Clinical manifestations were neck pain (n = 3) and limited range of motion (n = 4). Neurological examination noted brisk deep tendon reflexes (n = 6), positive Babinski reflex (n = 1) and positive Hoffmann reflex (n = 2). No patient had a neurological deficit. The conventional radiographs of the cervical spine showed: loss of cervical lordosis (n = 2), diastasis C1-C2 (n = 3), erosion of the odontoid process (n = 1), and anterior ankylosis (n = 3). Subsequent cervical spine MRI confirmed these findings and showed pannus at the craniocervical junction in one case and block vertebra of C6-C7 in another case. Atlanto-axial subluxation was anteroposterior in 3 patients and rotatory in one. Conclusion Cervical spine involvement is frequent and underestimated in JIA, and its radiological features are various. Hence, regular radiographic monitoring of the cervical spine is required to prevent the development of this complication.

Morphometric parameters of the odontoid process of C2 vertebrae, in Indian population, a CT evaluation

Background: Osteosynthesis of odontoid fractures, especially for type II odontoid fractures, is often achieved by the placement of screws. Here, utilizing CT, we evaluated the normal anatomy of the odontoid process in an Indian population to determine whether one or two screws could be anatomically accommodated to achieve fixation. Methods: CT-based morphometric parameters of the odontoid process were assessed in 200 normal Indian patients (2018–2020). Results: Of 200 patients, 127 were male, and 73 were female. The mean minimum external transverse diameter (METD) was 8.80 mm (range 6.1–11.9 mm). Six (3%) patients had a minimum internal transverse diameter (TD) of >8.0 mm that would allow for the insertion of two 3.5-mm cortical screws without tapping, while 10 (5%) patients had TDs of <7.4 mm; none had diameters of <5.5 mm. The mean length of the implant was 36.45 mm in females and 36.89 mm in males, and the mean angle of screw insertion was 60.34° in females and 60.53° in males. Conclusion: About two-thirds (59%) of the 200 subjects in our study had a METD of <9 mm, indicating the impracticality for introducing second screws for odontoid fixation.

Endoscopic Endonasal Versus Transoral Odontoidectomy for Non-Neoplastic Craniovertebral Junction Disease: A Case Series

BACKGROUND Odontoidectomy is a challenging yet effective operation for decompression of non-neoplastic craniovertebral junction disease. Though both the endoscopic endonasal approach (EEA) and the transoral approach (TOA) have been discussed in the literature, there remain few direct comparisons between the techniques. OBJECTIVE To evaluate the perioperative outcomes of EEA vs TOA odontoidectomy. METHODS A retrospective review of all cases undergoing odontoidectomy by either the EEA or TOA was performed. Attention was paid to the need for prolonged nutritional support, prolonged respiratory support, and hospitalization times. RESULTS During the study period between 2000 and 2018, 25 patients underwent odontoid process resection (18 TOA and 7 EEA). The most common indication for surgery was basilar invagination. Hospital length of stay, intensive care unit length of stay, and intubation days were all significantly shorter in the EEA group compared to the TOA group (P &lt; .01, P = .01, P &lt; .01, respectively). Prolonged nutritional support in the form of a gastrostomy tube was required in 5 patients and tracheostomy was required in 4 patients; all of these underwent odontoidectomy by the TOA. There was no statistical difference in neurological outcomes between the EEA and TOA groups (P = .17). CONCLUSION Odontoidectomy can be performed safely through both the EEA and TOA. The results of this study suggest the EEA has shorter hospitalizations and a lower probability of requiring prolonged nutritional support. These advantages are likely the results of decreased oropharyngeal mucosa disruption as compared to the TOA.

Periodontoid pseudotumoral lesions

Background: Periodontoid pseudotumoral lesions (PPL) are an uncommon cause of cervical pain and myelopathy. In addition, they may be associated with atlantoaxial instability (AAI). Case Description: Two patients over 60 years of age presented with neck pain alone. Their MR scans showed expansive lesions involving the odontoid process. One patient with AAI required an occipitocervical arthrodesis, while the other patient without instability was managed with an external orthosis (Philadelphia collar). Both of them experienced full resolution of pain and remained neurologically intact an average 36 months later (range 24–48). Conclusion: Here, we discussed the clinical, MR, and non-surgical (without AAI) versus surgical management (with AAI) for different types of PPL.

Surgical management of traumatic atlantoaxial subluxation in two cats

Case series summary We describe here the surgical management of two pure breed cats with traumatic atlantoaxial subluxation. One cat was ambulatory tetraparetic on presentation and the second was tetraplegic, both with cervical spinal pain and acute onset of paresis with subsequent deterioration. MRI was performed in both cases, demonstrating spinal cord injury. Flexed lateral cervical radiographs were needed to confirm atlantoaxial subluxation in one case. CT was performed for surgical planning and surgical stabilisation was achieved with threaded pins and polymethyl methacrylate (PMMA) cement; odontoidectomy was required in one case. Both cats showed improvement postoperatively, with no complications or deterioration seen. Following surgery, one cat made a complete recovery; however, the second cat retained significant deficits. Relevance and novel information We present the first report of surgically managed atlantoaxial subluxation of traumatic aetiology in cats, and report its occurrence in two novel breeds for this disease, Ragdoll and Persian. One case required odontoidectomy due to previous fracture and malunion of the odontoid process of the axis; both cases underwent surgical stabilisation of the atlantoaxial joint utilising multiple threaded pins and PMMA cement without transarticular implants – a technique that has not been previously reported in cats.

Cone Beam Computed Tomography Based Sex Estimation by Volume of Odontoid Process of The Second Cervical Vertebra

Objective: The aim of this study was to evaluate whether the volume of odontoid process of the second cervical vertebra on CBCT images can be used for sex estimation. Material and Methods: The volume of odontoid process on CBCT images of 138 subjects was measured. In addition, the patients were classified into five age groups. The comparisons between the groups in relation to sex and age were performed by using Mann-Whitney’s test and Kruskal-Wallis’ test, respectively. The ROC curve was used to assess the sensitivity and specificity of the volume to determine the sex. Results: No statistically significant difference was observed between age and volume. Males had significantly larger volumes than females. Values of volume equal to or greater than 1.254 mm3 have sensitivity of 68.2% and specificity of 68.1% to determine male sex. Conclusion: The volume of the odontoid process tends to be larger in males than in females and can be used as sex estimation. KEYWORDS Cone beam computed tomography; Diagnostic imaging; Sex determination processes; Image processing; Computer-assisted.