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OBJECTIVE To retrospectively evaluate the epidemiological and morphological features and outcome of surgical treatment of incomplete ossification of the dorsal neural arch of the atlas (IODA) in dogs with atlantoaxial instability (AAI). ANIMALS 106 AAI-affected dogs that underwent ventral fixation of the atlantoaxial joint. PROCEDURES Medical records and CT images for each dog were reviewed. Dogs were allocated to 1 of 2 groups on the basis of the presence or absence of IODA or of dens abnormalities (DAs) in CT images. RESULTS Of the 106 dogs with AAI, 75 had and 31 did not have IODA; 70 had and 36 did not have DAs. Incomplete ossification was present in the cranialmost, central, or caudalmost portion of the dorsal neural arch of the atlas in 59, 39, and 28 dogs, respectively; 2 or 3 portions were affected in 29 and 11 dogs, respectively. The mean CT value (in Hounsfield units) for the midline of the dorsal neural arch of the atlas in dogs with IODA was significantly lower than that for the same site in the dogs without IODA. The mean age at surgery for dogs with central IODA was significantly higher than that of the non-IODA group. The severity of spinal cord injury before or after atlantoaxial ventral fixation did not differ between the IODA and non-IODA groups. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that concomitant DAs or IODA is common in dogs with AAI. In dogs with incomplete ossification in the central part of the dorsal neural arch of the atlas, surgical treatment of AAI generally occurs at a middle to advanced age.

Purpose: The purpose of this study was to evaluate the clinical outcomes of atlanto-axial arthrodesis in rheumatoid arthritis (RA) patients with cervical myelopathy using the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ)., Methods: Twenty patients who underwent surgery to treat atlanto-axial subluxation (AAS) were reviewed., Results: The rates of success rates for each domain were as follows: cervical spine function, 11 of 18 patients (61.1%); upper extremity function, 3 of 15 patients (20%); lower extremity function, 8 of 18 patients (44.4%); bladder function, 5 of 13 patients (38.5%); and quality of life, 3 of 20 patients (15%). Significant differences of success rate were found between the following domains: cervical spine function and upper extremity function, cervical spine function and the quality of life, and lower-extremity function and quality of life. There were significant differences in the pre- and post-surgery visual analogue scale (VAS) scores for pain or stiffness in the neck or shoulders, and pain or numbness in the arms and hands., Conclusion: Atlanto-axial arthrodesis in RA patients provided a better outcome for cervical spine function, with improvement in VAS scores for pain or stiffness in the neck or shoulders. This surgery provided improvement of pain or numbness of the upper extremities but not of upper-extremity function. In contrast, the surgery achieved a relatively good recovery in lower-extremity function but little improvement of pain or numbness of the lower extremities. The success rate with regard to quality of life was found to be significantly lower than the success rates observed for cervical spine function and lower-extremity function., (Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.)