Computed tomography of the sacroiliac joints: comparison with complex-motion tomography

CT and gross pathology are comparable methods for detecting some degenerative sacroiliac joint lesions in dogs

Degenerative sacroiliac joint disease is a cause of lumbosacral pain in dogs; however, published information on cross-sectional imaging characteristics is limited. Objectives of this retrospective, secondary analysis, methods-comparison study were to test hypotheses that CT lesions reported in humans with degenerative sacroiliac joint disease are also present in dogs, and that CT is comparable to gross pathology for detecting these lesions. Matched CT and gross pathology slice images of 30 sacroiliac joints were retrieved from a previous prospective, canine cadaver study. A veterinary radiologist interpreted randomized CT images for each joint based on previously published CT characteristics of lesions in humans with degenerative sacroiliac joint disease. A veterinary pathologist independently interpreted randomized gross pathology images using the same criteria. All joints had at least one CT lesion consistent with degenerative sacroiliac joint disease. A new CT lesion was also identified and termed "subarticular cleft." The CT and gross pathology methods agreed for detecting joints with subchondral sclerosis, subchondral erosion, and intra-articular ankylosis lesions (P > .05, McNemar's test), but disagreed for detection of joints with subchondral cyst, para-articular ankylosis, and subarticular cleft lesions (P ≤ .05). Using gross pathology as the reference standard, CT had 100% sensitivity for detection of subarticular cleft and subchondral cyst lesions, with 56% and 22% specificity, respectively. Para-articular ankylosis lesions were detected by CT but not by gross pathology. Findings supported the hypothesis that CT lesions reported in humans with degenerative sacroiliac joint disease are also present in dogs, and partially supported the hypothesis that CT is comparable to gross pathology for detecting joints with these lesions.

Role of computed tomography in the evaluation of suspected sacroiliac joint disease

Computed tomography (CT) was compared with plain radiography in 41 examinations of selected patients with a clinical history suggestive of sacroiliac joint disease. The obliquity of the sacroiliac joints renders radiographic interpretation difficult. In the 41 cases who were examined with standard anteroposterior and posteroanterior radiographs of the sacroiliac joints, four were normal, eight abnormal and 29 were equivocal. Equivocal findings included indistinct and possibly irregular articular margins to the joints and subarticular sclerosis. Of the 29 equivocal studies, nine were normal on CT and 20 were abnormal. CT demonstrated definite changes of sacroiliac joint disease in 29 of the 41 examinations, 16 of which were sacroiliitis and 13 osteoarthritis. With plain radiography four of the eight abnormal studies were consistent with sacroiliitis, and four with osteoarthritis. It is concluded that CT is more sensitive than plain radiography in the evaluation of sacroiliac joint disease, and is especially valuable when there are equivocal plain radiographs.

Computed tomography evaluation of the sacroiliac joints in Crohn disease. Radiologic/clinical correlation

Computed tomography (CT) was used in a prospective study of the sacroiliac joints in 86 patients with Crohn disease to determine the type and frequency of sacroiliac joint abnormalities present in this population. The CT findings were correlated with review of the clinical history in 64 patients. Computed tomography demonstrated changes of sacroiliitis in 29% of the study group. This high prevalence of sacroiliac joint abnormality was found even in those under 30 years of age. It exceeds the 11-19% previously reported from plain film examination, reflecting the greater sensitivity of CT. In the subgroup of 64 patients studied clinically, 19 (30%) had abnormal sacroiliac joints on CT, but only 2 (3%) reported symptoms related to the sacroiliac joints.

Computed tomography of septic joints

Twenty-six patients with suspected or known septic joints who had been studied by computed tomography were retrospectively reviewed. Eighteen patients (20 joints) proved to have septic arthritis. Computed tomography was advantageous in patients with acute septic arthritis of deep-seated axial joints, such as the hip and sacroiliac, where it demonstrated particular soft tissue swelling as early as 36 hours after the onset of symptoms. In three patients, this finding on computed tomography was helpful in accurately localizing the disease process and facilitating a diagnostic closed needle aspiration biopsy procedure. Four patients had a primary osseous focus of infection in an adjacent epiphyseal region that was documented by computed tomography. Computed tomography was superior to conventional radiology in revealing early articular bone erosion in joints with curved and overlapping articular surfaces in five patients, and resulted in alteration of their treatment. Fat-fluid levels within the suprapatellar bursae were noted in one patient (two joints). Computed tomography is a valuable modality for evaluation of patients with suspected septic arthritis of axial joints, particularly in the acute stage. Furthermore, it is helpful for evaluation of possible periarticular abscess formation and can serve as a guide for a percutaneous drainage procedure. Computed tomography can also be used when articular bone erosion or medullary extension of osteomyelitis is suspected but not fully documented by conventional radiography.