MR Imaging of Rheumatic Diseases Affecting the Pediatric Population.

This article reviews the application of magnetic resonance imaging (MRI) to pediatric rheumatic diseases. MRI can detect early manifestations of arthritis, evaluate the extent of disease, and monitor disease activity and response to treatment.Juvenile idiopathic arthritis (JIA) is the most common pediatric rheumatic disorder, representing a diverse group of related diseases that share a definition of joint inflammation of unknown origin with onset before 16 years of age and lasting > 6 weeks. JIA may lead to significant functional impairment and is increasingly imaged with MRI to assess for active inflammation as a target for therapy. This is particularly true for juvenile spondyloarthritis that includes multiple subgroups of JIA and primarily involves the spine and sacroiliac joints.Other less common pediatric rheumatic diseases considered here are chronic recurrent multifocal osteomyelitis and collagen vascular diseases including polymyositis, dermatomyositis, scleroderma, and juvenile systemic lupus erythematosus.

Toward Developing a Semiquantitative Whole Body-MRI Scoring for Juvenile Idiopathic Arthritis: Critical Appraisal of the State of the Art, Challenges, and Opportunities.

With powerful new therapies available for management of juvenile idiopathic arthritis (JIA), early diagnosis leading to appropriate treatment may prevent long-term structural joint damage. Although magnetic resonance imaging (MRI) is typically used to assess individual body parts, indications for whole body (WB) MRI are increasing. Its utility as a diagnostic and monitoring tool has already been widely investigated in adult rheumatology patients, but less so in pediatric rheumatologic patients. This paper is a comprehensive review of scoring systems and a proposal for the conceptual development of a WB-MRI scoring system for the evaluation of JIA. In this review we identify, summarize, and critically appraise the available literature on the use of WB-MRI in inflammatory arthritis, addressing relevant considerations on components of a classification system that can lead to the development of a future pediatric WB-MRI scoring system for use in children with JIA. We also discuss advantages and challenges of developing such a WB-MRI scoring system for assessment of JIA and outline next steps toward the conceptual development of this scoring system.

ASAS definition for sacroiliitis on MRI in SpA: applicable to children?

BACKGROUND: The Assessment of Spondyloarthritis International Society (ASAS) definition for a 'positive' Magnetic Resonance Imaging (MRI) for sacroiliitis is well studied and validated in adults, but studies about the value of this definition in children are lacking. The aim of this study is to evaluate whether the adult ASAS definition of a positive MRI of the sacroiliac joints can be applied to children with a clinical suspicion of Juvenile Spondyloarthritis (JSpA). METHODS: Two pediatric musculoskeletal radiologists blinded to clinical data independently retrospectively reviewed sacroiliac (SI) joint MRI in 109 children suspected of sacroiliitis. They recorded global impression (sacroiliitis yes/no) and whether the adult ASAS definition for sacroiliitis was met at each joint. This was compared to gold-standard clinical diagnosis of JSpA. Additionally, MRI were scored according to'adapted' ASAS definitions including other features of sacroiliitis on MRI. RESULTS: JSpA was diagnosed clinically in 47/109 (43%) patients. On MRI, sacroiliitis was diagnosed by global assessment in 30/109 patients, of whom 14 also fulfilled ASAS criteria. No patients with negative global assessment for sacroiliitis fulfilled ASAS criteria. Sensitivity (SN) for JSpA was higher for global assessment (SN = 49%) than for ASAS definition (SN = 26%), but the ASAS definition was more specific (SP = 97% vs. 89%). Modifying adult ASAS criteria to allow bone marrow edema (BME) lesions seen on only one slice, synovitis or capsulitis, increased SN to 36%, 32% and 32% respectively, only slightly lowering SP. Including structural lesions increased SN to 28%, but lowered specificity to 95%. CONCLUSION: The adult ASAS definition for sacroiliitis has low sensitivity in children. A pediatric-specific definition of MRI-positive sacroiliitis including BME lesions visible on one slice only, synovitis and/or capsulitis may improve diagnostic utility, and increase relevance of MRI in pediatric rheumatology practice.

Reliability of 3D localisation of ACL attachments on MRI: comparison using multi-planar 2D versus high-resolution 3D base sequences.

PURPOSE: Anatomic placement of anterior cruciate ligament (ACL) grafts at arthroscopic reconstruction can be challenging. Localising ACL attachments on magnetic resonance imaging (MRI) sequences pre-operatively could aid with planning for anatomic graft placement. Though ACL attachments can be identified on two-dimensional (2D) MRI, slice thickness theoretically limits out-of-plane accuracy and a 3D MRI base sequence with smaller isotropic voxels may improve observer reliability in localising ACL attachment locations. The purpose of this study was to test whether a high-resolution 3D sequence improved inter- and intra-observer reliability of ACL attachment localisation compared with conventional 2D MRI for this application. METHODS: Twenty paediatric knees were retrospectively scanned at 1.5 Tesla with multi-planar 2D proton density (slice thickness 3-4 mm) and T2-weighted 3D multiple-echo data image combination gradient echo (isotropic 0.8 mm voxels) sequences. Two observers blinded to each others' findings identified ACL attachments on MRI slices, and 3D reconstructions showing ACL attachments were produced. ACL attachment centre locations and areas were calculated, and reliability assessed. RESULTS: Inter-observer variation of centre locations of ACL attachments identified on 3D versus 2D sequences was not significantly different (mean ± SD): 1.8 ± 0.6 versus 1.5 ± 0.7 mm at femoral attachments, 1.7 ± 0.7 versus 1.5 ± 0.8 mm at tibial attachments (p > 0.05). The 95 % confidence interval for centre locations was <4.0 mm in all cases. Inter-observer reliability of attachment areas was not higher for 3D sequences. CONCLUSIONS: ACL attachment centres were localised with high and similar inter- and intra-observer reliability on a high-resolution 3D and multi-planar conventional 2D sequences. Using this technique, MRI could potentially be used for planning and intra-operative guidance of anatomic ACL reconstruction, whether from 2D or 3D base sequences. Surgeons in clinical practice need not order a lengthy dedicated 3D MRI to localise ligament attachments, but can confidently use a standard 2D MRI for this application. LEVEL OF EVIDENCE: III.

MRI Anatomy of the Tibial ACL Attachment and Proximal Epiphysis in a Large Population of Skeletally Immature Knees: Reference Parameters for Planning Anatomic Physeal-Sparing ACL Reconstruction.

BACKGROUND: To aid in performing anatomic physeal-sparing anterior cruciate ligament (ACL) reconstruction, it is important for surgeons to have reference data for the native ACL attachment positions and epiphyseal anatomy in skeletally immature knees. PURPOSE: To characterize anatomic parameters of the ACL tibial insertion and proximal tibial epiphysis at magnetic resonance imaging (MRI) in a large population of skeletally immature knees. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: The ACL tibial attachment site and proximal epiphysis were examined in 570 skeletally immature knees with an intact ACL (age, 6-15 years) using 1.5-T proton density-weighted sagittal MRI; also measured were the tibial anteroposterior diameter; anterior, central, and posterior ACL attachment positions; vertical height of the epiphysis; and maximum oblique epiphyseal depth extending from the ACL tibial attachment center to the tibial tuberosity. RESULTS: In adolescents (11-15 years of age), the center of the ACL's tibial attachment was 51.5% ± 5.7% of the anteroposterior diameter of the tibia, with no significant differences between sexes or age groups (P > .05 in all cases). Mean vertical epiphyseal height was 15.9 ± 1.7 mm in the adolescent group, with significant differences between 11-year-olds (15.2 ± 1.5 mm) and 15-year-olds (16.6 ± 1.6 mm), P < .001, and between males (16.6 ± 1.5 mm) and females (14.8 ± 1.4), P < .001. Mean maximum oblique depth was 30.0 ± 5.3 mm, with a significant difference between 11-year-olds (26.7 ± 4.9 mm) and 15-year-olds (32.7 ± 5.1 mm), P < .001, and between males (29.7 ± 6.4 mm) and females (27.8 ± 5.2 mm), P < .001. The maximum oblique depth occurred at a mean angle of ~50°, and this angle did not change with age or sex. There was a significant moderate correlation (r = 0.39, P < .001) between epiphyseal vertical height and maximum oblique depth. CONCLUSION: The center of the ACL tibial attachment was consistently near 51% of the anteroposterior diameter, regardless of age or sex. The vertical depth of the tibial epiphysis was ~16 mm in adolescents. Maximum oblique depth from ACL attachment was ~30 mm, occurring at a mean angle ~50° regardless of age or sex. The normative values for tibial ACL attachment and epiphyseal anatomy presented here may be helpful in selecting candidates for surgery and in planning surgical approaches for pediatric ACL reconstruction.

Three-dimensional intercondylar notch volumes in a skeletally immature pediatric population: a magnetic resonance imaging-based anatomic comparison of knees with torn and intact anterior cruciate ligaments.

PURPOSE: To determine whether 3-dimensional notch volume, measured with magnetic resonance imaging (MRI), differs significantly between knees with torn and intact anterior cruciate ligaments (ACLs) after sports injury in a skeletally immature pediatric population. METHODS: MRI studies of 50 pediatric patients (age range, 10 to 17 years) with ACL tears were compared with 50 age- and sex-matched intact-ACL control patients. All patients had open physes and underwent MRI after a sports injury. Notch volume was calculated through manual segmentation of notch boundaries seen on axial 1.5-T proton density-weighted images. Two-dimensional (2D) measurements (notch width and notch width index) were made on coronal proton density-weighted MRI studies. Notch volume was compared between groups by use of the Mann-Whitney U test. Pearson correlation coefficients were also calculated between indices. RESULTS: Notch volume was significantly lower in knees with ACL tears than in control knees (5.5 ± 1.1 cm(3)v 6.4 ± 1.5 cm(3), P = .002), whereas 2D notch width and notch width index did not differ significantly between these groups. Girls had significantly smaller notch volumes than boys (5.4 ± 1.2 cm(3)v 6.5 ± 1.3 cm(3), P < .001). Notch volume was not correlated with age but was moderately correlated with 2D notch width (r = 0.485, P < .001). CONCLUSIONS: In adolescent patients with sports injuries, the 3-dimensional notch volume was significantly smaller in knees with ACL tears than in intact-ACL control knees. Notch volume was also significantly smaller in girls than in boys and did not vary significantly with age. LEVEL OF EVIDENCE: Level III, case-control study.

Reliability of estimates of ACL attachment locations in 3-dimensional knee reconstruction based on routine clinical MRI in pediatric patients.

BACKGROUND: Current techniques of anterior cruciate ligament (ACL) reconstruction focus on the placement of femoral and tibial tunnels at anatomic ACL attachments, which can be difficult to identify intraoperatively. PURPOSE: To determine whether the 3-dimensional (3D) center of ACL attachments can be reliably detected from routine magnetic resonance imaging (MRI) in patients with intact ACLs and whether the reliability of this technique changes if the ACL is torn. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: A computer technique was developed in which users identify points along ACL attachments on routine clinical MRI of preoperative knees. These attachments are then displayed on a 3D MRI reconstruction, which can be used as a visual guide for the surgeon during arthroscopic surgery. Thirty-seven pediatric patients (age range, 10-17 years) with ACL tears and 37 controls with intact ACLs were examined. Two blinded observers identified cruciate ligament attachments on routine clinical 1.5-T MRI of knees. From the resulting 3D model, the location of the center of each ligament attachment site and its area were calculated and reliability assessed. RESULTS: Mean interobserver variation of the centers of ACL attachments for the intact versus torn ACL was 1.7 ± 0.9 mm versus 1.8 ± 1.1 mm (femoral) and 1.4 ± 0.9 mm versus 1.7 ± 1.0 mm (tibial), respectively (P > .05). The 95% confidence interval for the center location was at most 4 mm. The identified ACL attachment areas were more variable, with interobserver reliability ranging from fair to excellent by the intraclass correlation coefficient. Overlap of ligament areas between observers for the intact versus torn ACL was 70% ± 15% versus 73% ± 12% (femoral) and 79% ± 9% versus 78% ± 10% (tibial), respectively (P > .05). In all cases, intraobserver reliability was superior to interobserver reliability. CONCLUSION: The 3D locations of ACL tibial and femoral attachment centers were identified from routine clinical MRI with variability averaging less than 2 mm between 2 observers. The margin of error was at most 4 mm, representing the thickness of a single axial MRI slice, whether the ACL was intact or torn. Remnant tissue at attachments allows a reliable assessment even of torn ligaments. Identification of the ligament attachment areas was more user dependent than was identification of the attachment centers.