Ankylosing Spondylitis
Ankylosing Spondylitis
Ankylosing Spondylitis
tendons of the spine and pelvis (axial skeleton), often resulting in complete polyarticular
ankylosis.
● Onset is usually between 15 and 35 years and involves males more than females.
Clinical Features
● chronic low back pain, relieving with activity.
● low back, with aching and stiffness of variable intensity localized to the sacrum,
Pathologic Features
✔ Synovial Articulations
synovial proliferation and inflammatory cell proliferative synovial tissue forms a layer over
the articular cartilage, resulting in its destruction and subchondral erosion of bone.
✔ Cartilage Articulations
initial changes occur in the subchondral bone as an osteitis extensive replacement of the involved bone and intra-articu
✔ Entheses
when an inflammatory cell infiltrate replaces the chondrified and calcified parts of the
ligament, resulting in bone erosion. Repair of the erosion is characterized by deposition of
woven bone, which projects away from the original surface, producing spur-like bony
spicules. Later, this is remodelled and replaced by lamellar bone
Radiologic Features
● The basic changes consist of osteoporosis, erosions, and surrounding reactive sclerosis,
-
- Reactive sclerosis, particularly in the adjacent ilium seen = most common stage
when diagnosis is first made.
Stage 3. Ankylosis.
- Narrowing and eventual obliteration of the joint space.
- Reactive sclerosis gradually dissipates replaced by generalized osteoporosis.
Occasionally, the anterior sacroiliac joint marginal cortex will remain visible through the
ankylosis and is referred to as a ghost joint.
The upper ligamentous portion of the joint will also demonstrate bridging ossification.
When prominent, it will be seen on an AP film as a triangular radiopacity (star sign)
Sacroiliitis grading (New York criteria) – based on
X-ray
Classification
● grade 0: normal
● grade I: suspicious changes (some blurring of the joint margins)
● grade II: minimum abnormality (small localized areas with erosion or
sclerosis, with no alteration in the joint width)
● grade III: unequivocal abnormality (moderate or advanced sacroiliitis
with erosions, evidence of sclerosis, widening, narrowing, or partial
ankylosis)
● grade IV: severe abnormality (complete ankylosis)
⮚ Spine (9 signs)
8. Trolley track spine - Three vertical lines seen in advanced case on the AP lumbar
film owing to ossification in the apophyseal joints and interspinous and supraspinous
ligaments
9. ossification of spinal ligaments, joints and discs (with fatty marrow within the ossified
disc, best seen on MRI)
10. apophyseal and costovertebral arthritis and ankylosis
11. enthesophyte formation from enthesopathy – whiskering enthesophytes
- Hip involvement is generally bilateral and symmetric, with uniform joint space
narrowing,
- axial migration of the femoral head sometimes reaching a state of protrusio
acetabuli, and
- a collar of osteophytes at the femoral head-neck junction.
● Pelvis
Whiskering of the pelvic bones primarily affects the ischial tuberosities, resulting from
ossification of the ligamentous origins.
● Knees
● Hands
Hands are generally involved asymmetrically, with smaller, shallower erosions and
marginal periostitis.
● Shoulders
demonstrates a large erosion of the anterolateral aspect of the humeral head, producing a
'hatchet' deformity
marrow oedema of the acromion process, at the site of origin of deltoid muscle, has been
described as a very specific sign of the disease
● Chest
- progressive fibrosis and bullous changes at the apices. These lesions may
resemble tuberculosis infection and bullae may become infected.
● Cardiac
- normal/ cardiomegaly.
CT
● chronic structural changes such as joint erosions, subchondral sclerosis, and bony
MRI
● may have a role in early diagnosis of sacroiliitis; MRI is more sensitive than CT or plain
Bone scintigraphy
● Ratios of SI joint to sacral uptake of 1.3:1 or higher is abnormal
Complications
1. fracture
increased chance of spinal fracture also known as "chalk stick" or "carrot stick fractures"
2. Andersson lesion
3. Arachnoid Diverticula
● Generalized dural ectasia in association with diverticula formation occurs appears
to be closely linked to the development of cauda equina syndrome.
● Lumbar spine is the most common site
● most diverticula are directed posteriorly and can erode the pedicles, lamina, and
spinous process
4. rare neurological complications include transverse myelitis and/or cauda equina
syndrome
TREATMENT
DD
● general spine: enteropathic arthritis and other seronegative arthritis