Objectives Beyond Our Scope Anatomy of the Sacroiliac Joint

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

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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

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Cross-sectional anatomy Radiological anatomy

Coronal oblique CT reformats

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)

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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.

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« 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

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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

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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

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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

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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)

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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.

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Lésions avérées (structural) Séméiologie

Inflammation Lésions organisées Actif ! Quiescent ! • Ostéite (œdème • Ostéo-sclérose médullaire) • Érosions • Synovite • Involution graisseuse • Capsulite • Ankylose • Enthésite • Ossifications péri- osseuses

Lésions avérées (structural) Lésions avérées (structural)

Erosion Erosion Ankylose Sclérose

Lésions avérées (structural) Structural changes  propensity to produce bone  fatty deposition/erosion/ossification near entheses and ankylosis  occur late in disease course  correlate poorly with symptoms  are better seen on radiographs/CT than MRI (except for fatty deposition)  remain poorly understood but could partly represent a healed or quiescent stage of inflammation.  do not suffice for the definition of a positive MRI if without inflammatory changes

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DISH – Forestier Ankylose Performance diagnostique IRM

Jans et al JBR 2014, 97: 202-205

Combinaison BME et autres signes

Conclusion

IRM performante pour détection lésions sacro-iliaques

Séquence minimum: SE DP fs (œdème ?) et SE T1 (graisse ?) plan coronal oblique

Approche holistique : Espace: Os sous-chondral, synoviale, capsule, enthèse Temps : phase active, phase quiescente

Jans et al JBR 2014, 97: 202-205

Chronic back pain ≥3 months with age at onset < 45

« imaging arm » « clinical arm » *Sacroiliitis on imaging:

Sacroiliitis* HLA-B27 + - Active (acute) inflammation on MRI highly suggestive of sacroiliitis associated with SpA And ≥ 1 SpA feature ** And ≥ 2 SpA features ** or

- Definite radiographic sacroiliitis according to modified ** SpA features: NY criteria

Inflammatory back pain Good response to Arthritis NSAIDs Enthesitis Family history of Uveitis SpA Dactylitis HLA-B27 + Psoriasis elevated CRP *** Crohn’s disease /Ulcerative Colitis

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Sémiologie IRM

• Topographie articulaire – Tiers moyen et antérieur – Autres territoires – Variantes • Association simultanée de plusieurs phases – Active aigue – Active chronique – Quiescente

DP fs

Synovite

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Sacro-iliite septique Généralement affection aiguë (mais diagnostic tardif) Radiographies peu contributives Sacro-iliite septique:

• Pathologie relativement rare • Diagnostic clinique difficile • Population à risque • Grossesse • Immunodéprimé • Utilisation de drogue Atteinte unilatérale, Prévalence destruction sur reconstruction érosions floues et peu/pas de sclérose trabéculaire.

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Sacro-iliite septique Généralement affection aiguë (mais diagnostic tardif) Radiographies peu contributives (ou d’interprétation délicate)

Limited articular recesses Strong capsule/ligament

Look at distance for fluid/abcesses !

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Sacro-iliite septique Généralement affection aiguë (mais diagnostic tardif) Radiographies peu contributives

Atteinte unilatérale, Prévalence destruction sur reconstruction érosions floues et peu/pas de sclérose trabéculaire.

Sacro-iliite septique Sacro-iliite septique - TDM Généralement affection aiguë (mais diagnostic tardif) Radiographies peu contributives (ou d’interprétation délicate)

Anatomy of the immature SI interface

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Spatial orientation of SI interface

Frontale plane

Variations observed in sacro-iliac joint anatomy

Fused joint Sacro-iliac joint complex Sacral defect Acessoty sacro-iliac joint

Transverse plane