Background
Advantages of MSUS in children
Imaging modality | Advantages | Limitations |
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MSUS | Lack of exposure to ionizing radiation Rapidity of performance Ease of repeatability High patient acceptability Demonstration of soft tissue inflammation Direct visualization of cartilage Early detection of bone erosions Ability to scan multiple joints in a single session Support in guidance of procedures (e.g. intra- articular corticosteroid injections) Relatively inexpensive | Difficulties in carrying out in case of severe joint limitation Relatively small field of view Inability to assess the whole joint space Acoustic shadowing from overlying bones Limited value in the assessment of axial skeleton and temporomadibular joints Dependency on the properties and sensitivity of the ultrasound equipment Need of continuous practice after appropriate training Reliability, standardization and validation in children under investigation |
MRI | Lack of exposure to ionizing radiation Multiplanar tomographical imaging Ability to assess the whole joint space Demonstration of soft tissue inflammation Direct visualization of cartilage Early detection of bone erosions Visualization of bone marrow oedema High tissue contrast Suitable for assessment of axial skeleton and temporomadibular joints | Intravenous contrast agent often required Possible allergic reaction to contrast agents General anesthesia required in younger children Long examination time Evaluation limited to one target joint Reliability, standardization and validation in children under investigation High cost Variable availability worldwide |
Conventional radiology | Rapidity of performance Applicability to all joints Demonstration of joint space narrowing, disturbances of bone growth and maturation Detection of bone erosions Validated scoring methods in children Suitable for longitudinal evaluation of damage progression Low cost Widespread availability | Exposure to ionizing radiations Inability to directly visualize cartilage and soft tissue inflammation Late detection of bone erosions and joint space narrowing Projectional superimposition |
Challenges with MSUS in children
Usefulness of MSUS in children
What is the evidence for usefulness of MSUS in JIA?
Subclinical synovitis and tenosynovitis
Enthesitis
ILAR classification JIA subgroups
Definition of disease remission
Imaging guided injections
Cartilage damage
Bone erosions
Advances and perspectives
Conclusions
Key points
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MSUS can detect inflammatory changes more frequently than the clinical examination and can visualize their exact location in joints of children with different JIA ILAR subtypes, yielding important insights in the extent, pathophysiology and classification of childhood arthritis.
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Due to the unique features of the growing skeleton, accurate knowledge of MSUS findings over time in children is warranted. Currently, validated definitions of MSUS features in joints of healthy children are available; standardization of scanning techniques specific for the pediatric population and definitions of MSUS pathological findings in children are ongoing.
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Correlation of MSUS findings with biologic markers, clinical features and other imaging tools should be studied prospectively to investigate the clinical meaning and prognostic value of MSUS-detected abnormalities in different joints at different time points of the disease course.
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Despite the astounding interest in the use of MSUS in children, only few pediatric rheumatologists currently perform MSUS on their own. Further educational activities for suitable training and mentorship in MSUS in children are advisable in the future.