1/22/2020 European Course on Spine Radiology ESNR & ESSR Rome 2020 Objectives • The normal spine: Complex anatomy of the SI interface • Implications for imaging of SI joints Anatomy of the sacroiliac joint – Radiographs – CT/MRI B. Vande Berg, J. Malghem, S. Acid, T. Kirchgesner, V. Perlepe, F Lecouvet • Implications for analysis of SI joints – Radiograpic evaluation – CT/MRI evaluation Beyond our scope By the end of this presentation, you should • MRI and CT features of SI joint disorders • coop with the anatomy of mature and immature SI joints and variants • Advanced MR imaging (contrast, diffusion…) • understand implications for imaging techniques • Treatment monitoring • Be aware of anatomy-related pitfalls • Interventional radiology Anatomy of the sacroiliac joint 1 1/22/2020 Normal sacro-iliac joint anatomy • L- or C-shaped articular surfaces (auricular surfaces) on sacrum and iliac bones • with thick sacral and thin iliac articular cartilage • covering thin sacral and thick iliac subchondral bone plates • anterior and inferior segments of SI interface Auricular surface sacral tuberosity Normal sacro-iliac joint anatomy Comparative anatomy of intervertebral disc and sacro-iliac joint • Fibrous SI joint without cartilage • with thick ligaments Intervertebral disc Sacro-iliac joint • Posterior and superior segments of SI interface Central antero-inferior thick nucleus pulposus layer of fluid in articular space No synovium synovium Peripheral Postero-superior annulus fibrosus fibrous interface fibrous connective tissue fibrous and fatty connective tissue Thin cartilaginous end-plate Thick cartilaginous end-plate Zygapophyseal joints No zygapophyseal joints Strong ligaments and muscles Strong ligaments and muscles Cross-sectional anatomy Transverse oblique CT reformats S1 S2 S3 2 1/22/2020 Cross-sectional anatomy Radiological anatomy Coronal oblique CT reformats S1 S2 Limitations of radiographic assessment • No lateral view • Overlapping soft tissues and bones S3 • No assessement of articular recesses • Oblique and serpiginous orientation of articular surfaces • (poor visibility of subchondral bone) Radiological anatomy Radiological anatomy Anterior Anterior Posterior Posterior Cranial Cranial Intermediate Intermediate Caudal Caudal Cranial segment of SI joint Intermediate segment of SI joint • cartilaginous and fibrous joint bony overlap • Cartilaginous and fibrous interface and posterior aspect of iliac wing • Frontal orientation poor conspicuity of sub. bone • Frontally orientated (limited conspicuity of subchondral bone) • Frequent ligament ossifications • Frequent degenerative changes Radiological anatomy Radiological anatomy Anterior Anterior Posterior Posterior Cranial Cranial Intermediate Intermediate Caudal Caudal Caudal segment of SI joint Posterior segment of SI joint • only cartilaginous joint less bony overlap • Cartilaginous and fibrous interface • sagittal orientation conspicuity of subchondral bone • Frequent accessory sacro-iliac joints • No degenerative changes (more specific if involved) 3 1/22/2020 Normal sacroiliac joint Anatomical variations of SI joints MRI 157 patients Variants to be aware of Frequency (pts) 1 Normal sacroiliac joint 68% 2 Isolated SI synostosis 1% Anatomical variations of the normal SI joints 3 Unfused apophysis 0% 4 Accessory SI joint 11% 5 Iliosacral complex 11% Immature sacro-iliac joint 6 Sacral defect 13% 7 Dysmorphic changes 17% Ligamentous ossifications Sacroiliac joints: anatomical variations on MR images Mazen El Rafei et al Eur Radiology 2018; 28: 5328-5337 https://doi.org/10.1007/s00330-018-5540-x Bilateral ilio-sacral complex Unilateral right sacral defect • Prominent ilium • Flat ilium Normal sacroiliac joint • Depressed sacrum • Depressed sacrum • Vascular engorgement • Vascular engorgement Variants to be aware of Anatomical variations of the normal SI joints Immature sacro-iliac joint Ligamentous ossifications Sacroiliac joints: anatomical variations on MR images Mazen El Rafei et al Eur Radiology 2018; 28: 5328-5337 https://doi.org/10.1007/s00330-018-5540-x A-C vs D Kappa 0,49 Chauvin NA et al, MRI of the Sacroiliac Joint in Healthy Children. AJR Am J Roentgenol. 2019 Apr 11:1-7. doi:10.2214/AJR.18.20708. 4 1/22/2020 « SI joint cortical irregularities » Normal SI joints • 57% of patient/joints 15-year-old girl • Iliac/sacrum: 51%/11% • Upper/lower : 43%/27% • No age difference • Kappa: 0,20 SE T1 fs PD Chauvin NA et al, MRI of the Sacroiliac Joint in Healthy Children. AJR Am J Roentgenol. 2019 Apr 11:1-7. doi:10.2214/AJR.18.20708. SE T1 fs PD Normal SI joints Normal SI joints 17-year-old girl 20-year-old man SE T1 fs PD fs PD Normal SI joints Normal SI joints 23-year-old man 23-year-old man Subtle bilateral and symetrical changes Compatible with metaphyseal-equivalent changes SE T1 fs PD Gd-enh. fs SE T1 fs PD Gd-enh. fs SE T1 SE T1 fs PD Gd-enh. fs SE T1 , SE T1 fs PD Gd-enh. fs SE T1 5 1/22/2020 Normal sacroiliac joint Ligament ossification Variants to be aware of Anatomical variations of the normal SI joints Immature sacro-iliac joint Ligamentous ossifications Anatomy-related pitfalls at SI imaging Anatomy-related pitfalls at SI imaging Soft tissue involvement in SI diseases Soft tissue involvement in SI diseases Trans-articular extent by bone tumors • very limited articular space thight capsule Abcess at distance from the joint Septic sacroiliitis T2 Septic sacroiliitis T2 T1 T1 T1 + Gd T1 + Gd 6 1/22/2020 Septic sacroiliitis Deux mois plus tard, T1 T2 T1 T2 T1 + Gd T1 + Gd Anatomy-related pitfalls at SI imaging InflammatorySPA ou vs neoplasticseptique ? ? Trans-articular extent by bone tumors If involvement of both sides, check the articular part of the joint • Inflammatory diseases may involve the cartilage • Neoplastic diseases spare the cartilage InflammatoryTumeur vs neoplastic! ? Gd enh. SE T1 Fs PD Lymphoma Articular component of SI interface is preserved Articular component of SI interface is preserved Interosseous extension through fibrous joint Interosseous extension through fibrous joint 7 1/22/2020 Preserved of inferior aspect of SI interface (cartilage) InflammatoryInfection vs neoplastic – tumeur ? ? Involvement of posterior aspect of superior segment of SI interface (fibrous) Hypernephroma metastasis CONCLUSION Notions • Squelette immature • Anatomy of SI joints – Mature (>25 yrs) • Variantes anatomiques – immature SI joints • Atteintes non spécifiques – variants • Fréquence des anomalies dans la population • understand implications for imaging techniques « normale » – Transverse and coronal oblique planes – Fibrous vs cartilaginous joint • Be aware of anatomy-related pitfalls Buts IRM Technique IRM • Détecter lésions • Lésions actives – inflammation - Œdème – Actives séquence pondérée T2 avec fat-sat – Quiescentes • Explorer tous les territoires cibles • Lésions quiescentes - Involution graisseuse – Enthèses (insertions tendons, ligaments aponévroses) séquence pondérée T1 avec graisse – Os sous chondral – Synoviales – Capsules articulaires 8 1/22/2020 Suppression signal de la graisse Comment suis-je certain d’avoir un Terminologie bon examen ? • STIR • Dans séquence • Plan coronal oblique T1 (graisse blanche) • T2 fs • Avant séquence • Plan coronal oblique T2 avec fat sat (eau blanche et graisse • DP fs noire) • Dixon, Ideal, mDixon • Plan transverse oblique T1 ou T2 • Grappa, Blade… • Après séquence Technique IRM Injection iv de Gd ? • Injection de Gd améliore la détection de • Lésions actives – inflammation - Œdème – Synovite (différencie liquide articulaire (avasculaire) de la synoviale épaissie (vascularisée) séquence pondérée T2 avec fat-sat – Enthésites – capsulite • Injection de Gd n’améliore pas la détection de – Ostéite • Lésions quiescentes - Involution graisseuse – Érosion séquence pondérée T1 avec graisse • Injection de contraste n’augmente pas la détection des patients atteints car atteinte isolée de la synoviale (sans ostéite) est très rare. • SE T1 fat-sat avec contraste ? • NB En recherche, quantification de la perfusion ? Monitoring ? • NB attention pourrait être différent au rachis ! Mandatory MRI sequences for SI imaging Séméiologie T1-weighted SE coronal oblique sequence Anomalies tardives Anomalies précoces Fat-saturated intermediate-weighted SE coronal oblique sequence Lésions structurales Inflammation Optional MRI sequences for SI imaging • Rx • IRM T1-weighted and fat-suppressed intermediate-weighted SE transverse oblique sequences (optional). • CT Gadolinium enhanced fat-saturated T1-weighted sequence (optional) Fat-saturated T1-weighted sequence or gradient-echo T2*- weighted sequence (optional) 9 1/22/2020 Inflammation Séméiologie IRM Inflammation Lésions organisées Synovite • Ostéite (œdème • Ostéo-sclérose médullaire) • Érosions Ostéite • Synovite • Involution graisseuse • Capsulite • Ossifications péri- Enthésite • Enthésite osseuses Ostéite : signal élevé en T2 fs dans deux secteurs différents sur une coupe dans un secteur sur deux coupes Inflammation Ostéite Enthésite Inflammation Bone Inflammation (osteitis) Appears as bone marrow edema occurs early in disease course correlates with symptoms is detected exclusively at MRI presents as high signal intensity on fat-saturated fluid- DP fs T1 fs Gd sensitive sequences needs to be visible at least on 2 consecutive slices or 2 foci on Synovite Erosion et synovite same slice for a definite diagnosis in sacro-iliac joints. 10 1/22/2020 Lésions avérées (structural) Séméiologie Inflammation Lésions organisées Actif ! Quiescent ! • Ostéite (œdème • Ostéo-sclérose