The gross and radiographic appearance of sacroiliac ankylosis capsularis ossea in the dog

The prevalence of sacroiliac joint CT and MRI findings is high in large breed dogs

Sacroiliac joint (SIJ) disease has been described as one of the possible causes of lumbosacral (LS) region pain in dogs. However, published information is currently lacking for the computed tomographic (CT) and magnetic resonance imaging (MRI) characteristics of canine SIJ disease. The objectives of this retrospective, observational study were to describe and quantify CT and MRI SIJ findings in a sample of large breed dogs and test associations between the numbers of SIJ findings and other variables. Data archives for a veterinary teaching hospital were searched for large breed dogs (≥ 22.7 kg) that had CT or MRI scans of the LS and pelvic regions in 2015-2019. Dogs with a history of acute trauma or scans with incomplete SIJs were excluded. A veterinary student recorded medical record findings. A veterinary radiologist and graduate student recorded CT and MRI findings based on previously published criteria in dogs and humans. Fifty-three dogs were sampled (20 CT, 33 MRI). Categories of findings with the highest prevalence were subchondral erosion (100% CT, 100% MRI) and subchondral sclerosis (95% CT, 97% MRI). The total numbers of SIJ findings per dog were not associated with dog age, sex, weight, or concurrent findings in the LS or pelvic regions. The total number of MRI SIJ findings per dog differed between German Shepherds and Labrador Retrievers (P = 0.0237) as well as between Labrador Retrievers and other breeds (P = 0.0414). These results indicated that CT and MRI findings reported in humans with SIJ disease are common in large breed dogs.

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.

Feasibility and accuracy of ultrasound-guided sacroiliac joint injection in dogs

Frozen cadaver specimens from three dogs were used to create a sectional anatomic atlas of the sacroiliac region. Frozen/thawed cadaver specimens from 12 dogs were used to develop an ultrasound-guided sacroiliac joint injection technique. Accuracy of the technique was tested in 15 additional canine cadaver specimens, using injectate containing blue dye and iodinated contrast medium. Sonoanatomic landmarks for consistently identifying a caudodorsal window into the canine sacroiliac joint space included the L7-S1 articular process joints, ilial wing, sacral wing, sacral lamina, and median sacral crest. Accuracy of ultrasound-guided sacroiliac joint injection was not significantly affected by operator, but was affected by the tissue location targeted and the reference standard used for calculations. Accuracy of the technique was good for placing injectate into either the synchondrosis component, dorsal sacroiliac ligament or ventral sacroiliac ligament; fair to poor for placing injectate into the synovial component; and poor for placing injectate into all four sacroiliac soft tissue structures. Concurrent placement of injectate into extraarticular tissues occurred frequently. We conclude that ultrasound-guided sacroiliac joint injection is feasible for evaluation as a treatment method for lumbosacral region pain in dogs, but is not sufficiently accurate for localizing pain to the sacroiliac joint alone.