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Infectious sacroiliitis: MRI- and CT-based assessment of disease extent, complications, and anatomic correlation
Sarah Interligator1, Antoine Le Bozec2, Guillaume Cluzel1
1Department of Radiology, Hôpital Bicêtre, Assistance-Publique des Hôpitaux de Paris, 78 rue du Général Leclerc, 94270 Le Kremlin-Bicêtre, Paris, France.
Objective:
To describe the frequency of MR and CT features of infectious sacroiliitis (ISI) and assess its extent and complications MATERIALS AND METHODS: This retrospective study included patients with ISI who were evaluated between 2008 and 2021 in a single center. Two radiologists reviewed MRI and CT images to determine the anatomical distribution (unilateral/bilateral, iliac/sacral bone, proximal/middle/distal), severity (bone marrow edema [BME]/periostitis/erosions), concurrent infection (vertebral/nonvertebral), and complications (abscess/probable adjacent osteomyelitis/cavitation/devitalized areas/sequestrum/pelvic venous thrombosis) of ISI. Interobserver reproducibility was assessed. Correlation analysis evaluated the effect of the causative microorganism on severity. Two human bodies were dissected to outline possible ways that ISI can spread.
Results:
Forty patients with ISI (40 years ± 22; 26 women) were evaluated. Ten patients had bilateral ISI. Concurrent vertebral infection was associated in 15% of cases. Reproducibility of sacral BME, periostitis, and reactive locoregional abnormalities was perfect (κ = 1). Reproducibility was low for erosion count (κ = 0.52[0.52-0.82]) and periarticular osteopenia (κ = 0.50[0.18-0.82]). Inflammatory changes were BME (42/42 joints), muscle edema (38/42), and severe periostitis along the ilium (33/37). Destructive structural changes occurred with confluent erosions (iliac, 20/48; sacral, 13/48), sequestrum (20/48), and cavitation (12/48). Complications occurred in 75% of cases, including periarticular abscesses (n = 30/47), probable adjacent osteomyelitis (n = 16/37), and pelvic thrombophlebitis (n = 3). Tuberculous ISI (6/40) correlated with sclerosis (rs = 0.45[0.16; 0.67]; p < 10-2) and bone devitalization (rs = 0.38[0.16; 0.67]; p = .02). The anatomical study highlighted the shared venous vascularization of sacroiliac joints, pelvic organs, and mobile spine.
Conclusion:
Complications of ISI are frequent, including abscesses, adjacent osteomyelitis, and periostitis. ISI had bilateral involvement nonrarely and is commonly associated with another spinal infection.
Insights
Infectious sacroiliitis (ISI) frequently leads to complications like abscesses and osteomyelitis, often involving bilateral sacroiliac joints and concurrent spinal infections. Imaging features help assess disease extent and spread.
Area of Science:
- Radiology
- Infectious Diseases
- Orthopedic Surgery
Background:
- Infectious sacroiliitis (ISI) is a serious condition affecting the sacroiliac joints.
- Understanding its imaging features, extent, and complications is crucial for effective management.
Purpose of the Study:
- To detail the frequency of magnetic resonance imaging (MRI) and computed tomography (CT) findings in infectious sacroiliitis (ISI).
- To evaluate the anatomical distribution, severity, and complications associated with ISI.
- To explore potential routes of ISI spread through anatomical dissection.
Main Methods:
- Retrospective analysis of 40 patients with ISI evaluated between 2008 and 2021.
- Review of MRI and CT images by two radiologists to assess anatomical distribution, severity, concurrent infections, and complications.
- Interobserver reproducibility assessment and correlation analysis between causative microorganisms and disease severity.
- Anatomical dissection of two human bodies to illustrate ISI spread pathways.
Main Results:
- Forty patients (40 years ± 22; 26 women) were included, with 10 showing bilateral ISI and 15% having concurrent vertebral infection.
- High interobserver reproducibility for bone marrow edema and periostitis; lower for erosion count.
- Common findings included bone marrow edema (100%), muscle edema (90%), and severe periostitis (89%).
- Complications occurred in 75% of cases, notably periarticular abscesses (64%), adjacent osteomyelitis (43%), and pelvic thrombophlebitis (6%).
- Tuberculous ISI correlated with sclerosis and bone devitalization.
Conclusions:
- Complications such as abscesses, adjacent osteomyelitis, and periostitis are frequent in infectious sacroiliitis.
- Bilateral involvement and association with spinal infections are not uncommon in ISI.
- Imaging plays a key role in diagnosing and characterizing the extent and complications of ISI.
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