Radiographic features of atlantoaxial joint in dogs
Date Issued
2009
Date
2009
Author(s)
Chen, Hsiang-ju
Abstract
英文摘要
Atlantoaxial instability (AAI) refers to the instability of the atlantoaxial joint (AAJ) that leads to dorsal displacement of the axis relative to the atlas, causing spinal cord compression. Diagnosis is based on clinical signs, signalment, history and imaging findings. Definitive diagnosis is made by demonstrating the consequence of atlantoaxial instability, such as the apparent increase in space between the dorsal spinous process of the axis and the dorsal arch of the atlas in the survey lateral radiographs, atlantoaxial misalignment causing spinal cord compression in myelography or magnetic resonance imaging (MRI), and the abnormal position of atlantoaxial joint in computed tomography (CT).
In some patients, the radiographic findings are not obvious and further investigations with advanced imaging would be required to achieve the diagnosis. However, the availability of the advanced imaging facilities, higher expense for the owner and the risk of general anesthesia would all potentially be the owner’s concern regarding the further investigations. To our knowledge, there are only few studies describing the motility of the atlantoaxial joint in dogs. The objective of this study include: 1) to establish the reference of the distance of the AAJ of predisposed breed dogs in three lateral projections (extended, neutral and flexed), 2) to demonstrate the motility of the AAJ of predisposed breed dogs and non-predisposed breed dogs, 3) to compare radiographic findings in dogs without AAI and clinically affected dogs, and 4) to establish a diagnostic criteria of AAI based on radiographic findings.
In total, 46 dogs were included in study one and were divided into three groups. Group one included 26 AAI-predisposed breed dogs which were not affected by AAI (six Yorkshire terriers, seven Pomeranian dogs, seven Chihuahua dogs and six Maltese terriers). Group two included 14 AAI-non-predisposed breed dogs which were not affected by AAI (seven miniature Dachshunds and seven beagles). Six AAI clinically affected dogs of predisposed breed were included in Group three (one Yorkshire terrier, one Pomeranian dog, two Chihuahua dogs and two Maltese dogs). Cervical spine radiographs were obtained in neutral, extended and flexed lateral projections and ventrodorsal projection. Five methods including the distance of atlantoaxial joint (AAD), horizontal movement (HM), vertical movement (VM), cranial to cranial (Cr’-Cr’) and caudal to cranial (Cd’-Cr’) were used to measure the distance between the atlas and the axis in three lateral views. The length of dens and axis were measured in the ventrodorsal view.
In Group one, the distance of the atlantoaxial joint significantly changed between three lateral projections (p<0.05), and no significant changes were found in Group two. In all three lateral projections, VM and Cd’-Cr’ of the atlantoaxial joint in Group two was significantly increased compared to that in Group one (p<0.05). In neutral and flexed lateral projections, AAD and Cr’-Cr’ of the atlantaoxial joint in Group three were significantly increased compared to that in Group one (p<0.05).
In study two, based on the data analysis of study one, a diagnostic criteria of AAI was generated. Twelve veterinarians were asked to interpret radiographs of 12 dogs (six dogs in Group one and six dogs in Group three) based on their own experience (first stage) and based on the AAI diagnostic criteria (second stage). The diagnostic rate based on the AAI diagnostic criteria was significantly higher.
In conclusion, the study demonstrated that the motility of the AAJ exists in several AAI-predisposed breed dogs. The reference range of the distance between atlas and axis in several breed dogs were also established. The AAI diagnostic criteria generated from the study is user friendly, and its application would increase the diagnostic rate of AAI.
Subjects
dogs
atlantoaxial instability
radiology
diagnosis
dens
Type
thesis
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