Contribuições cirúrgicas para o tratamento da instabilidade atlantoaxial em cães

Abstract

The aim of the first study was create an alternative method of surgical access to the atlantoaxial joint by ventral access without sternothyroid muscle section. A total of 15 dogs, weighing between eight and 12 kg were randomly divided in three groups according to postoperative period (PO), GI (30days), G II (60) and G III (90 days). The atlantoaxial joint was submitted to arthrodesis through the ventral access using Steinmann pins associated to acrylic resin. The access and exposure of the atlantoaxial joint without sternothyroid muscle section were completed without complications or additional limitations. None dog in this study had cough, dyspnea, regurgitation, laryngeal paralysis or Horner's syndrome. It can be concluded that the section of the sternothyroid muscle is an unnecessary procedure and does not interfere in the exposure of the atlantoaxial joint and in the arthrodesis of dogs through ventral access. The aim of the second study was test and compare the homogenous cancellous bone preserved in 98% glycerin in dogs submitted to atlantoaxial arthrodesis. Twelve dogs, weighing between 8 and 12 kg were randomly divided into three groups. Group I (GI): performed only the removal of joint cartilage and joint immobilization with acrylic resin and pins. Group II (GII): after removal of joint cartilage and immobilization, was performed the modeling and the placement of the homogenous cancellous bone at the determined location. The volume of homograft placed in the joint was measured using a precision balance and all animals received the same quantity. Group III (GIII): was performed the same procedure of the GI, however, was used autogenous cancellous bone graft at the determined location. Radiographic examinations were performed on all animals at 30, 60 and 90 days postoperatively. At 90 days of PO was carried out the 9 euthanasia of the animals to perform manual palpation test and CT and histological evaluation. For statistical analysis of the association between the degree of joint fusion, assessed by manual palpation, digitized radiographic images and CT scans and treatment groups, we applied the Chisquare test of independence. The test results were evaluated by the exact significance and considered statistically significant at 5% significance (p <0.05). By manual palpation test and by the CT images can be seen that there was no statistically significant difference between groups at 90 days postoperatively. Radiographic analysis of the atlantoaxial joint showed that the degree of fusion was similar among treatments, without statistical difference at 30, 60 and 90 days postoperatively. In relation to histopathology study at 90 days postoperatively, was found that bone formation in group I had 25% of each intensity (absent, mild, moderate, severe), in group II 75% mild and 25% severe, and in group III, 25% moderate and 75% severe. It can be concluded that the use of graft homogenous preserved in 98% glycerin in dogs undergoing atlantoaxial fusion method is a viable alternative for treatment of atlantoaxial instability. It can be also conclude that there is no difference in the degree of fusion was performed only removal of joint cartilage, suggesting this may be an alternative treatment of atlantoaxial instability.