ANKYLOSING SPONDYLITIS RADIOLOGY

1. ANKYLOSING SPONDYLITIS

2. • INTRODUCTION
• CLINICAL PRESENTATION
• PATHOLOGY WITH PATHOPHYSIOLOGY
• IMAGING
• COMPLICATIONS
• DIFFERENTIALS
• LABORATORY TESTS
• TREATMENT

3. INTRODUCTION
• Ankylosing Spondylitis is a chronic inflammatory
rheumatological disorder that predominantly
affects the axial skeleton
Characterized by
1.SACROILITIS
2.SPONDYLITIS
3.ENTHESITIS
• Most common cause of seronegative spondylo arthritides a
group of disorders that are rheumatoid factor negative and
are frequently associated with the presence of HLA B - 27
antigen

4. • Men > Women ( 15 -30 years )
• Teen age to young adulthood
• Ankylosing Spondylitis affects both synovial and cartilaginous joints and
entheses and is manifested by a combination of osseous erosions ,new bone
formation and ultimately leads to ankylosis
• Previously known as Bechterew’s disease ,Marie Strumpell disease
• Other seronegative arthropathies include Psoriatic arthritis ,erosive arthritis
,reactive arthritis ,enteric arthritis

5. TYPES
MOST COMMON( SKELETAL LOCATIONS)
1.SACROILIAC JOINT
2.SPINE
OTHER COMMON SITES
 HIPS
 SHOULDER
 KNEE

6. CLINICAL PRESENTATION
 Characterized by insidious inflammatory low back pain worse in morning and after inactivity
 Improves with exercise
 Other clinical features are stiffness ,limited mobility and pain over protuberances secondary to
enthesitis
 In advanced stage
 A thoracic kyphotic deformity with head and neck protruded forward and chest excursion due to
ankylosis of chest
 Anterior uveitis – common association

7. ETIOLOGY
Cause of disease is unknown, though interaction between infectious agent possibly
Klebseilla and the HLA B -27 antigen( 90 % of patient )

8. PATHOGENESIS
TNF alpha ,Bone morphogenetic proteins and prostaglandins contribute to the process
PLASMA CELLS
,LYMPHOCYTES
INFILTRATE JOINT
AFFECT BOTH SYNOVIAL
AND LIGAMENTOUS
PORTION
INITIALLY
SUBCHONDRAL EDEMA
,SYNOVITIS , JOINT
EFFUSION
INFLAMMATORY
INFILTRATES LEAD TO BONY
EROSIONS
HEALING WITH NEW BONE
FORMATION ANKYLOSIS

9. PROGRESSION OF DISEASE
 AS typically begins at SI joints ,generally ascending through the spine from lumbar to
cervical although it may skip levels
 Peripheral joints are less commonly involved ,with mainly the large joints ,the HIPS AND
SHOULDERS
 Small joint disease is uncommon
ENTHESITIS – Hall mark pathological change in AS ,which is characterized by pathological cells causing
inflammatory changes and finally destruction of the entheses ( the attachment of ligaments , tendons ,fascia
and capsules to bone )
SCLEROSIS
SYNDESOPHYTE FORMATION

10. SACROILIAC JOINT – AS

11. FINDINGS
 LOSS OF DEFINITION OF SUBCHONDRAL BONE PLATE
 SUBCHONDRAL EROSIONS
 A WIDENED JOINT SPACE( Initially there is widening of SI joint space which narrows as disease progresses)
 REACTIVE SCLEROSIS AROUND JOINT
 FINAL STAGE – ANKYLOSIS ( Joints may completely disappear in the final stage with ankylosis and
remodelling )
 Ligamentous compartment of SI joint affected by bony erosion and enthesial proliferation markedly made
out in MRI

12. PLAIN RADIOGRAPH
 Sacrolilitis is the first manifestation, ( often first location involved in radiographs),symmetrical and bilateral
 KEY FEATURE- BILATERAL ,SYMMETRICAL INVOLVEMENT
 ILIAC side of joint shows changes first due to thinner cartilage compared to sacrum

13. XRAY VIEW FOR SI JOINT
 In plain XRAY – SI joint may be difficult to assess
radiologically du to obliquity of the joint and
obscuration by overlying soft tissues
 A modified FERGUSON AP view best depicts this
articulation
 Patient positioned supine on the imaging tables
with legs extended
 Elevate the side of interest approximately 25 to 30
degree
 FERGUSON VIEW FOR SI JOINT – A modified AP
pelvis xray with the central xrays angled in a
cephalad manner and directed at the midline 5 cm
below the ASIS

14. GRADING OF SACROILITIS
ACCORDING TO NEW YORK CRITERIA
GRADE 0 – NORMAL
GRADE I- SUSPICIOUS CHANGES (SOME BLURRING OF JOINT MARGIN)
GRADE II- MINIMUM ABNORMALITY ( SMALL LOCALIZED AREAS WITH EROSION OR SCLEROSIS
,WITH NO ALTERATION OF JOINT WIDTH )
GRADE III – UNEQUIVOCAL ABNORMALITY ( MODERATE OR ADVANCED SACROILITIS WITH
EROSIONS ,E/O SCLEROSIS ,WIDENING ,NARROWING,OR PARTIAL ANKYLOSOSIS)
GRADE IV – SEVERE ABNORMALITY (COMPLETE ANKYLOSIS),Significant narrowing or complete loss
of joint space

15. GRADE 1 – Some blurring of joint margin
GRADE 2 – Minimal sclerosis with erosion s

18. Frontal xray in chronic b/l sacroilitis resulted in partial ankylosis

19. Frontal radiograph of SI joint
showing b/l symmetric sacroiliitis
with erosions creating a widened
appearance of joints and
subchondral sclerosis

20. SIGNS -SI
 ROSARY BEAD SIGN – EROSIVE APPERANCE OF SI JOINT
 STAR SIGN – FUSION /ANKYLOSIS OF THE SUPERIOR ASPECT OF SI JINT
 GHOST JOINT – COMPLETE SI JOINT FUSION ,NO VISIBLE JOINT

21. ROSARY BEAD SIGN – Small erosions lined up one behind
the other at corresponding sites of ilium and sacrum ,
resembling a string of beads or rosary
STAR SIGN – Fusion or ankylosos of
the superior aspect of SI joint

22. CT of patient SI joint showing
subchondral erosions and sclerosis Another patient CT with SI joint ankylosis

23. MRI
MRI findings ( SI ) include
MRI features of sacroiliitis can be divided into inflammatory and structural lesions
1.inflammatory lesions
1. Marrow oedema (first to appear): high signal on water sensitive sequences,low on T1 and post contrast enhancement
enhancement
2. Synovitis and Capsulitis: thickening and contrast enhancement of the synovium and joint capsule
3. Enthesitis: thickening and contrast enhancement of ligaments and tendons at their attachments to bone
Structural lesions
•Subchondral sclerosis: bands of low signal (on all sequences) parallelling the joint margins, at least 5 mm from the joint space
the joint space
•Erosions: marginal foci of articular bone loss
• low T1 signal
• high T2/STIR signal if active
• more prominent anteroinferiorly and on the iliac side of the SIJ
• when confluent may appear as joint space widening
•Fat metaplasia: periarticular fat deposition
•Ankylosis

25. Acute SI in another young man ,Gadolinium enhanced contrast fat
Saturated Images showing enhancement of connective fibrous tissue

26. Another T2 axial image of patient showing subchondral erosions, joint
space widening with effusion and subchondral sclerosis

27. Axial T1 and STIR images in a patient with AS – Post inflammatory
fatty infiltration after acute sacroilitisT1 hyperintensity s/o fatty
marrow infiltration

28. T2 W image showing b/l Symmetrical pattern
of subchondral bone marrow edema and
enthesitis at gluteus maximus attachments.T1
showing hypointense signal s/o marrow
edema ,T2 showing erosions

29. ASAS CLASSIFICATION CRITERIA –ACTIVE SACROILITIS
ON MRI
ASSESSMENT IN SPONDYLOARTHRITIS INTERNATIONAL SOCIETY (ASAS) CLASSIFICATION CRITERIA
REQUIRED CRITERIA NOT REQUIRED CRITERIA
Bone marrow edema /osteitis on a T2 W or bone
marrow enhancement on a T1
Inflammation must be clearly present and localized in
a typical anatomical area (subchondral bone)
MRI appearance must be suggestive of a
spondyloarthropathy
The sole presence of other inflammatory lesions like
synovitis ,enthesitis or capsulitis without BMO is not
sufficient for definition of active sacroiliitis in MRI
In the absence of BMO ,presence of advanced signs
like sclerosis ,erosion or ankylosis do not meet
definition od sacroiliitis in MRI

30. AS -SPINE
 In spine involvement ,AS is characterized by osteitis , syndesmophyte formation ,
,facet inflammation , and eventual facet joint and vertebral body fusion

31. AS - SPINE
EARLY CHANGE – Early spondylitis is
characterized by small erosions at the
corners of vertebral bodies with reactive
sclerosis – ROMANUS LESIONS ( It
typically develops at the site of
attachment of annulus fibrosis to the
anterior corner of vertebral endplates )
SHINY CORNER SIGN
Spinal finding in AS , associated with
INACTIVE ROMANUS LESIONS ( HEALING
STAGE ) – reactive sclerosis secondary
to the inflammatory erosions at superior
and inferior end plates

34. • Next important radiological
sign is squaring of vertebra
• Pathophysiology – The
anterior borders of vertebra
may appear squared due to
periosteal proliferation of the
new bone filling in the normal
concavity or erosion at
vertebral margins

35. • ANDERSON LESIONS -
• INFLAMMATORY LESIONS at the junction
of intervertebral disc and the vertebral
endplate can lead to interbody ankylosis
(Non infectious spondylodiscitis )

36. ANDERSON LESION - MRI T1 ,STIR and T1 PC FAT SAT images shown below, we can see high
signal intensity of hemispherical shape involving the central portion of vertebra and the discs
showing hyperintense signal in STIR ,hypointense on T1 and post contrast enhancement

37. BAMBOO SPINE
• BAMBOO SPINE APPEARANCE- Diffuse syndesmophytic ankylosis
• Syndesmophytes are vertically oriented projection of bone that develop due to
ossification within the outer fibers of annulus fibrosis
• Syndesmophytes are radiologically visible on anterior and lateral aspects of
spine starting from corner of vertebra
• The progressive growth of syndesmophyte bridge the intervertebral disc
causing ankylosis
• Peripheral ankylosis resulting from the syndesmophytes and spinal ligament
ossification and central ankylosis through disc and facet joints ,cause
appearance of spine as a fused osseous column – BAMBOO APPEARANCE

41. SYNDESMOPHYTE
• Paravertebral ossification ,caused
by ossification of annulus fibrosis
• Oriented vertically
• USUALLY SYMMETRICAL- Origin at
the edge of one vertebral body
extending to the margin of
adjacent vertebral body
• However , bridging osteophytes
and large syndesmophytes can
appear similar
OSTEOPHYTE
• Paravertebral ossification , horizontal
orientation
• Marginal osteophytes are horizontal
bony extension of vertebral endplate
and non marginal are horizontal
extension of vertebral body 2-3 mm
away from endplate

44. PARA SYNDESMOPHYTES
 Aka Non marginal bulky syndesmophytes or
floating syndesmophyte are paravertebral
dystrophic soft tissue calcifications or
heterotopic ossifications
 Known to be seen in Psoriatic arthritis or
reactive arthritis
 Often asymmetrical
 On radiography , initially parasyndesmophytes
begin at a distance from the vertebral body
and intervertebral space
 Ultimately they increase in size to form large
and bulky masses ,merging with the
underlying bones and disc

45. • DAGGER SPINE- Linear
ossification along the
central spine ,representing
the interspinous ligament
can give a dagger spine
appearance
• Combination fo Bamboo
spine and dagger spine
called as trolley track sign

47. ROLE OF MRI IN SPINE
 May have a role in early diagnosis of sacroiliitis;
MRI is more sensitive than CT or plain radiography in detecting inflammatory changes (which precede structural changes) such as bone marrow
oedema (best demonstrated on STIR sequences), synovitis and capsulitis (on gadolinium enhanced T1 weighted sequences)
 Synovial enhancement on MR correlates with disease activity measured by inflammatory mediators
 Enhancement of the interspinous ligaments is indicative of enthesitis
 Superior to CT in the detection of cartilage inflammation and destruction
 Useful in following treatment results in patients with active ankylosing spondylitis

48. Another young man with AS .MRI showing
Romanus anterior spondylitis ,Anderson
spondylodiscitis , hyperintensity of facet
joint s/o edema and arthtritis
Post contrast image showing discrete
enhancement of interspinal and
supraspinal ligaments

49. Another CT image of AS
patient showing Romanus
anterior spondylitis ,Anderson
spondylodiskitis
,zygapophyseal joint arthritis
,sclerosis and erosions of
vertebral endplates

50. Another AS patient Cervical spine xray (lateral xray ) showing posterior vertebral
body syndesmophytes ,ankylosis of the facet joints from C2 to T1 and
interlaminar and interspinous ankylosis

51. OTHERS
 Apophyseal and costovertebral arthritis and
ankylosis
 Enthesiophyte formation ( bony proliferations that
can occur at entheses , Can be mistaken for
osteophytes
 Ankylosed spine susceptible to fractures
 Pseudoarthroses aka false joint ( mobile fracture
non union ) can occur at fracture sites
 Dural ectasia- Ballooning or widening of the dural
sac which can result in posterior vertebral scalloping
and associated with herniation of nerve roots

52. BASRI SCORING (BATH ANKYLOSING
SPONDYLITIS RADIOLOGY INDEX SCORE )
0- Normal
1- Suspicious ( No definite change)
2- Mild – (Any number of erosions ,squaring , or sclerosis, with or without
syndesmophytes ( on more than or equal to 2 vertebra)
3- Moderate – (Syndesmophytes on more than or equal to 3 vertebra ,with or without
fusion involving 2 vertebra)
4- Severe – fusion involving more than 3 vertebra

53. AS -PELVIS
• WHISKERING of the pelvic bones mainly
the ischial tuberosity resulting from
ossification of ligamentous origins
• There can be bridging and fusion of
pubic symphysis

54. AS - HIP
 Hip involvement is generally
b/l and symmetric
 Uniform joint space narrowing
 Axial migration of femoral
head sometimes reaching a
stage of protrusion
acetabuli,and a collar of
osteophytes at the femoral
head –neck region

55. Bilateral enthesitis manifested by the subchondral bone marrow edema within
each greater trochanter and edema within enthesis of gluteus medius tendons

56. SHOULDERS
 Glenohumeral joint involvement is not
uncommon , and demonstrates a large
erosion of the anterolateral aspect of the
humeral head ,producing a HATCHET
DEFORMITY
 Marrow edema of the acromion process
,at the site of origin of deltoid muscle ,has
been described very specific for the
disease

57. CHEST -THORACIC
MANIFESTATION OF AS
 It can affect tracheobronchial tree and lung parenchyma and disease
spectrum includes
 Upper lobe fibrocystic changes – fibrobullous disease
 Early involvement may be unilateral or asymmetrical
 Most cases eventually consist of bilateral apical fibrobullous lesions
 Most can be progressive with coalesecence of nodules
 Formation of cysts and cavities ,fibrosis and bronchiectasis occur
 Uncommon findings – Pleural thickening ,chest wall restricted
mobility

59. CARDIOVASCULAR
MANIFESTATIONS
 Aortic root dilatation
 Aortitis
 AR
 Pericarditis
 Myocardial involvement – Left and right ventricular
dysfunction
 Cardiomegaly
 Conduction disturbances especially AV node

60. OTHER ASSOCIATIONS WITH
AS
1.ANTERIOR UVEITIS- MC
2.PSORIASIS
3.INFLAMMATORY BOWEL DISEASE
4.OSTEOPENIA
5.SECONDARY AMYLOIDOSIS ( RARE)
6.CAUDA EQUINA SYNDROME ( RARE
)

61. COMPLICATIONS
Fractures
Patients with AS with diffuse paraspinal ossification and inflammatory osteitis creates a
fused brittle spine ,which has risk of fracture even with trivial trauma
More common at the cervicothoracic and thoracolumbar regions
CHALK STICK FRACTURE OR CARROT STICK FRACTURE
Fractures of fused spine ,usually occur at the discoveretbral junction in lower cervical or
upper thoracic spine
Chalk stick fracture can also be seen in other conditions of fused spine like DISH ,PLL
ossification ,surgical spine fusion
Anderson lesion ( Inflammatory spondylodiscitis can further result in pseudoarthrosis
Rare neurological complications like Transverse myelitis and cauda equina syndrome

63. DIFFERENTIALS
1. GENERALIZED SPINE – ENTEROPATHIC ARTHRITIS
2. CERVICAL SPINE – JUVENILE RHEUMATOID ARTHRITIS
3. DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS
4. OPLL ( Ossification of PLL )
5.Hyperparathyroidism ( SI joint space widening more marked)

64. DISH( DIFFUSE IDIOPATHIC
SKELETAL HYPEROSTOSIS )
 Pathological process characterized by diffuse calcification and
ossification of ALL
RADIOLOGICAL
 Frequently involve the cervical and thoracic spine
FLOWING OSSIFICANS
 Florid ,flowing ossification along the anterior
aspect or right aspect of at least five
contiguous vertebra
 Left lateral aspect usually spared thought due
to aortic pulsation inhibiting ossification
 Disc spaces are usually preserved
 Ankylosis is more common in thoracic than
cervical or lumbar spine’
 No sacroiliitis or facet joint ankylosis noted

65. ANKYLOSING SPONDYLITIS DISH OPLL
Both anterior and posterior
longitudinal ligaments are
involved
Thin calcifications contiguous
with ‘ SYNDESMOPHYTES ‘
Diffuse
Anterior longitudinal
ligament only
Prominent flowing anterior
osteophytes involving > 4
joints
Most common in lower
thoracic spine
PLL only
Thin or thick linear sheet of
calcification
Cervical or upper thoracic
spine

66. PSORIATIC ARTHRITIS
Also a seronegative arthropathy
Involves SI joint – however asymmetrical
Other radiographic features
 Acroosteolysis
 Periositis –
 Enthesitis and marginal bone erosions – pencil in
cup deformity ( Pathognomonic )
 Bone proliferation around joint
 Ivory phalanx
 Arthritis mutilans
 Sausage digit – dactylitis can present as sausage
digit refers ti soft tissue swelling of entire digit
 Spondylitis – asymmetric paravertebral
ossification and relative sparing of digits

67. REACTIVE ARTHRITIS
 Tends to involve distal lower extremity more
commonly( knee > metatarsophalangeal
joint > calcaneus >ankle > SI)
 Enthesitis may develop at the calcaneus at
the site of achilles tendon and plantar fascia
attachment
 A large bulky paravertebral area of
ossification – :” Floating osteophytes” often
seen
 Sacroiliitis –asymmetrical

68. BRUCELLOSIS
Another miscellaneous condition that can affect spine
It causes unilateral sacroiliitis
Can also cause spondylodiscitis,bursitis and osteomyelitis

69. CLINICAL TEST AND
MANGEMENT
 Schober's test – A useful clinical measure of flexion of lumbar spine
performed during examination
 Medications used are NSAIDS ,DMARDS TNF alpha blockers
 Surgical management – Osteotomy for marked deformities or occasionally
arthtroplasty may be used