7 Positive clinical associations with intraarticular gas include degenerative disc disease, cervical vertebral instability, osteochondrosis, and degenerative joint disease ( Fig. Interestingly, gas diffusion was not a feature of normal (non-OCD) contralateral joints of dogs in this series. 7, 8 Gas diffusion is likely induced by traction while positioning the shoulder for OCD examination. ) and is observed when excessive distraction is applied to the coxofemoral joints during distraction radiography and has been reported in 20% of shoulder radiographs in dogs with osteochondritis dissecans (OCD) of the humeral head. Vacuum phenomenon has many causes in dogs and cats ( Box 21.2 This may occur naturally or be induced by applying traction to a joint. 9 Current theory is that noniatrogenic intraarticular gas represents diffusion of nitrogen from extracellular fluid into an adjacent joint space when negative pressure is present in the joint. The presence of intraarticular gas is identified more easily during computed tomography (CT) examinations than during radiography. 6, 7, 8, 9, 10 It has also been observed within the intervertebral disc spaces of dogs at sites of disc prolapse. Spontaneous or induced gas diffusion into a joint, termed the vacuum phenomenon, has been reported in both horses and dogs. When stifle synovial mass increases, either from increased synovial fluid or soft tissue, a combination of inflammatory response and effusion causes the shape of the fat pad to be altered and the fat pad to become less visible. The normal infrapatellar fat pad is identified readily on lateral stifle radiographs as a relatively radiolucent triangular region immediately caudal to the patellar ligament ( Fig. In the stifle, the infrapatellar fat pad sign may be used to evaluate synovial volume. In most joints, an increase in synovial mass appears as periarticular soft tissue swelling, which is identified radiographically by the increased opacity of affected soft tissues. The joint cartilage, synovial fluid, synovial membrane, and joint capsule cannot be differentiated, because they are all of soft tissue opacity and therefore silhouette with one another. Any moderate increase in joint capsular or intracapsular soft tissue volume may be detected on good-quality radiographs.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |