Common incidental findings on sacroiliac joint MRI in children clinically suspected of juvenile spondyloarthritis

Rate of Unexpected Findings in Adolescent Lumbar Magnetic Resonance Imagings Ordered by Orthopaedic Surgeons

Background

The use of advanced imaging in children is increasing and unexpected findings (UFs) are often detected. The present literature lacks studies investigating the rate of UFs in pediatric lumbar spine magnetic resonance imagings (MRIs) and the sequelae of these findings. This study aimed to determine the overall incidence of UFs in adolescent lumbar MRIs, characterize these findings, stratify UFs based on patient characteristics, and determine any influences on patient treatment plans.

Methods

Medical records of 1409 patients aged 10 to 18.5 years old that had a lumbar MRI ordered by an orthopaedic surgeon from 2010 to 2020 were reviewed retrospectively. Demographics, insurance, reason for MRI, and change in treatment plans were noted. Unexpected findings were characterized as spinal cord, infra-peritoneal, retroperitoneal, peritoneal, or vascular-related. The relationship between patient characteristics and UFs was investigated using a t test and Chi-square test. The statistical relationships between UFs and treatment plan changes were evaluated using generalized linear models with a log link and a binomial error distribution.

Results

The average age of the 1409 patients was 15.5 years (95% CI: 15.4, 15.6). Back pain (90.1%) was the most common reason for lumbar MRI. Thirty-five UFs were found in 33 patients (2.3%): 19 were spinal cord-related, 15 were peritoneal-related, and one was vascular. Eight peritoneal findings involved the kidneys: two atrophy, two hypoplasia, two renal cysts, one pelvic kidney, and one hydronephrosis. Five patients had a syrinx, and two had spine tumors. Out of 33 patients with UFs, 11 required a change in treatment plan (33.3%). Back pain was not associated with an increased risk of UF. Patients with an UF on MRI had 2.60 times higher odds of experiencing a change in treatment plan.

Conclusions

The prevalence of UFs was 2.5% on lumbar MRIs and were mainly spinal cord or retroperitoneal-related. UFs were associated with an altered treatment plan 33% of the time and were unrelated to standard demographic characteristics or insurance type.

Key Concepts

(1)Overall, 33.3% of patients with an unexpected finding had a change in treatment plan.(2)Unexpected findings should be interpreted in the context of the patient's overall clinical picture, symptoms, and health to help elucidate the next steps in treatment.(3)The clinical significance of unexpected findings needs to be further studied.

Level of Evidence

Level III, Retrospective.

Effect of Characteristic Inflammatory and Structural Pelvic Magnetic Resonance Imaging Lesions on Expert Assessment of Axial Juvenile Spondyloarthritis

OBJECTIVE

To evaluate the influence of pelvic magnetic resonance imaging (MRI) findings on axial disease assessment in juvenile spondyloarthritis (JSpA).

METHODS

This was a cross-sectional study of patients with JSpA with suspected axial disease. Three experts reviewed each case and rated their confidence (-3 to +3) in the presence of axial disease, first with clinical data and second with clinical and MRI data. Agreement was defined as ≥ 2/3 clinical experts with a rating of ≤ -1 or ≥ 1, and high confidence agreement as ≤ -2 or ≥ 2. The association of clinical features and both global assessments was tested with modified Poisson regression models.

RESULTS

Two hundred seventy-two of 303 cases (89.8%) achieved agreement with clinical data alone. Adding imaging data affected agreement in 38.9% (118/303) and directionality of agreement in 23.4% (71/303). Agreement was facilitated in 26/31 cases and lost in 21/272 cases. Of those 71 cases that changed directionality, 33 changed from axial disease being absent to present and 38 from present to absent. The final model had an area under the receiver-operating characteristic (AUROC) curve of 0.93 and 3 factors were independently associated with expert agreement (HLA-B27: relative risk [RR] 1.41, 95% CI 1.14-1.74; pain improvement with activity: RR 1.27, 95% CI 1.05-1.54; and bone marrow edema on MRI: RR 4.08, 95% CI 2.91-5.73).

CONCLUSION

The addition of imaging data affected directionality and improved high confidence agreement of expert assessment of axial disease. These results underscore the integral role of MRI in the determination of axial disease in JSpA.

Common incidental findings on sacroiliac joint MRI: Added value of MRI-based synthetic CT

PURPOSE

To determine the prevalence of incidental findings on sacroiliac joint MRI and to determine the added value of MRI-based synthetic CT in the detection and evaluation of these incidental findings.

METHOD

In this retrospective study 210 patients clinically suspected of spondyloarthritis who underwent MRI of the sacroiliac joint with synthetic CT sequence were included. The images were reviewed by two radiologists in consensus for the prevalence of sacroiliitis, incidental findings, and the ability of synthetic CT and the conventional MRI to detect and diagnose these findings.

RESULTS

In 44.7% of patients sacroiliitis was present. In 89.0% of patients MRI showed at least one incidental finding other than sacroiliitis. Degeneration of the sacroiliac joint was the most prevalent finding (140 patients, 66.6%). The most frequent incidental findings outside the sacroiliac joint were facet joint degeneration (29.0%), disc degeneration (25.2%), enostosis (19.5%) and lumbosacral transitional vertebrae (14.3%). A total of 788 lesions was recorded and synthetic CT was found to be problem solving or necessary for diagnosis in 543 (68.9%) of these lesions. 42.1% of lesions were not visible on conventional MRI (T1 TSE and STIR), most often degenerative osteophytes in the sacroiliac joint or lower lumbar spine.

CONCLUSION

Incidental findings are seen more frequently on sacroiliac joint MRI than sacroiliitis, which is relevant as some will have clinical significance or require treatment. Nearly half of these incidental lesions were only visible on synthetic CT, which additionally has been shown to be problem solving for diagnosis in many other cases.

Outcomes in Juvenile-Onset Spondyloarthritis

Some studies have suggested children with juvenile onset spondyloarthritis (JoSpA) have a relatively poor outcome compared to other juvenile idiopathic arthritis (JIA) categories, in regards to functional status and failure to attain remission. Thus, in the interest of earlier recognition and risk stratification, awareness of the unique characteristics of this group is critical. Herein, we review the clinical burden of disease, prognostic indicators and outcomes in JoSpA. Of note, although children exhibit less axial disease at onset compared to adults with spondyloarthritis (SpA), 34–62% have magnetic resonance imaging (MRI) evidence for active inflammation in the absence of reported back pain. Furthermore, some studies have reported that more than half of children with “enthesitis related arthritis” (ERA) develop axial disease within 5 years of diagnosis. Axial disease, and more specifically sacroiliitis, portends continued active disease. The advent of TNF inhibitors has promised to be a “game changer,” given their relatively high efficacy for enthesitis and axial disease. However, the real world experience in various cohorts since the introduction of more widespread TNF inhibitor usage, in which greater than a third still have persistently active disease, suggests there is still work to be done in developing new therapies and improving the outlook for JoSpA.