SERONEGATIVE SPONDYLOARTHROPATHIES

A group of musculoskeletal syndromes linked by common clinical features and common immunopathologic mechanisms.

Negative to rheumatoid factor and mostly involve the axial skeleton.

Most have positivity to the HLAB27 gene.

Five subgroups of spondyloarthritis:

Ankylosing spondylitis

Psoriatic arthritis

Reactive arthritis (Reiter syndrome)

Enteropathic arthritis (i.e. extra-intestinal manifestation of IBD)

Undifferentiated spondyloarthritis

Case 1. 27 yr old male with low backache

Ankylosing spondylitis (AS) is a chronic, multisystem inflammatory disorder involving primarily the sacroiliac (SI) joints and the axial skeleton.

ANKYLOSING SPONDYLITIS

96% of patients are HLA-B27 positive .

Men:women 3:1

Age of onset typically between 20 and 40 years.

More commonly involves the axial skeleton, although peripheral joints may also be affected.

ANKYLOSING SPONDYLITIS

Signs and symptoms:Insidious onset of low back pain - The most common symptom

Fatigue-- 2nd most common symptom.

Presence of symptoms for more than 3 months.

Symptoms worse in the morning or with inactivity.

Extra-articular manifestations of AS can include the following:UveitisCardiovascular diseasePulmonary diseaseRenal diseaseNeurologic diseaseGastrointestinal (GI) disease

RADIOLOGIC FINDINGS:

The diagnosis of AS is generally made by combining the clinical criteria of inflammatory back pain and enthesitis or arthritis with radiologic findings.

Plain Radiography:

Sacroiliac involvement is typically bilateral and symmetric.

Spine involvement is often centered at the thoracolumbar or lumbosacral junction.

Spine involvement is characterized by

osteitis,

syndesmophyte formation,

facet inflammation, and eventual

facet joint and vertebral body fusion.

Initially, there is indistinctness and discontinuity of the thin white subchondral bone plate.

Progresses to gross bone erosions.

adjacent bone is often sclerotic and joint space narrowing and bone fusion eventually occur.

“Squaring of the vertebral bodies”

One of the early radiographic signs of enthesitis.

caused by erosions of the superior and inferior margins of vertebral bodies, resulting in loss of the normal concave contour of the anterior surface.

“Shiny corner sign (Romanus lesion)”

The inflammatory lesions at vertebral entheses may result in sclerosis of the superior and inferior margins of the vertebral bodies.

“ Bamboo spine” 

Thin and slender syndesmophytes are generally evident, representing ossification of the outer layer of the annulus fibrosis.

On AP lumbar spine radiographs the syndesmophytes thicken,become continuous giving knobbly appearance.

“Dagger sign”

On AP radiographs of the lumbar spine Ossification of the posterior interspinous ligaments produces a dense radiopaque line.

“Trolley-track sign”

The combination of the fused facets and ossification of the interspinous ligaments.

Facet joint inflammation leads to indistinctness and narrowing of the involved joint progressing to fusion.

Disk calcification may also occur, possibly due to relative immobilization of the vertebral column.

“Andersson lesion”

Localised destructive lesion of vertebral end plates with disc narrowing and marked reactive sclerosis.

Hip involvement is usually bilateral in distribution.

Uniform joint space loss

acetabular protrusion,

subchondral cysts, and

a rim of osteophytes about the femoral neck.

Bone erosions and remodelling in the antero lateral aspect of the humerus produce a “hatchet” appearance.

Computer Tomography:may be useful in selected patients with normal or equivocal findings on sacroiliac joint radiographs.

joint erosions, subchondral sclerosis, and bony ankylosis are better visualised on CT.

supplements scintigraphy in evaluating areas of increased uptake.

superior to radiographs and MRI in demonstrating injuries.

imaging modality of choice in patients with advanced disease having suspicion of spine fracture.

MRI when radiographs are normal or equivocal, MRI can be useful in the diagnosis of sacroiliitis by showing joint fluid and marrow edema.

MRIsuperior to CT in detection of cartilage, bone erosions, and subchondral bone changes.

useful in follow up of active disease.

synovial enhancement on MR correlates with disease activity measured by inflammatory mediators.

enhancement of the interspinuous ligaments is indicative of an enthesitis.

Decreased T1,increased T2 signal & enhancement on post contrast sequences correlate with edema or vascularized fibrous tissue.

Sagittal T1, T2 fat-sat & contrast-enhanced T1 images of the lumbar spine show signal alterations in anterosuperior corner of L4 and L5 vertebrae.Axial T2-fat-sat MR image passing through L5 body confirms the corner lesion & the corresponding axial CT scan demonstrates the corner erosion of vertebral endplate surrounded by spongiosclerosis.

BONE SCANmay be helpful in selected patients with normal or equivocal findings.

quantitative analysis is more useful.

ratios of SI joint to sacral uptake of 1.4:1 or higher is abnormal.

Case 2. 20 yr old female with red scaly rash.

Etiology is considered to be a combination of environmental and hereditary factors.

60% of patients being HLA-B27 positive.

Approx. 10%–15% of patients with skin manifestations of psoriasis will develop psoriatic arthritis.

Usually such manifestations will precede the development of arthritis.

Psoriatic arthritis

The hallmarks of psoriatic arthritis are signs of inflammatory arthritis combined with

bone proliferation,

periostitis,

enthesitis.

RADIOLOGIC FINDINGS

In the hands, wrists, and feet, a distal distribution is characteristic.

Findings may be bilateral or unilateral and symmetric or asymmetric.

“Sausage digit”Diffuse fusiform swelling of a digit due to involvement of several joints in a single digit.

“Fuzzy” appearance or “whiskering”Bone proliferation produces an irregular and indistinct appearance to the marginal bone about the involved joint.

“Pencil and cup” The erosions can cause a "pencil in cup" deformity where one articular surface is eroded creating a pointed appearance; the other articulating bone becomes concave, resembling an upside down cup.

Pencil and cup

“Ivory phalanx”Involvement of the distal phalanges (especially in the first digit) in the foot with sclerosis, enthesitis, periostitis, and soft-tissue swelling.

Periostitis It may appear as a thin periosteal layer of new bone adjacent to the cortex, a thick irregular layer, or irregular thickening of the cortex itself.

Joint subluxation may also be present.

Sacroiliac joint involvement is usually bilateral, either symmetric or asymmetric in distribution.

SI joints will show signs of inflammation with an indistinct subchondral bone plate or osseous erosions,

joint space irregularity & mild widening,

eventual joint space narrowing & fusion.

The thoracolumbar spine may show large comma-shaped paravertebral ossifications.

The facet joints are relatively spared, and there is absence of vertebral body squaring.

Other sites of joint involvement include the knees , elbows, ankles, and joints about the shoulders.

Case 3. 30 yr old male with symptoms of urethritis.

Also called Reiter’s syndrome, is a sterile inflammatory arthritis.

follows enteric or urogenital infection.

Associated with urethritis and conjunctivitis.

80% seropositive for the HLA-B27 antigen.

most common in young men aged 25–35 years.

REACTIVE ARTHRITIS

The features allowing differentiation between reactive arthritis and psoriatic arthritis relate to

clinical history,

patient sex and age, and

distribution of joint involvement.

Radiographic features:

In appendicular skeleton distribution may be unilateral or bilateral and symmetric or asymmetric.

Affects feet more commonly than hand and also in more severe form.

Findings seen in the hands, wrists, and feet include joint inflammation, bone proliferation,

periostitis, and

enthesitis,

Calcaneal enthesitis and spur formation occurs in 35-40%.

Sausage digit and pencil-and-cup deformities may also occur.

In the feet, an ivory phalanx may be seen.

Axial involvement may also occur, leading to bilateral symmetric or asymmetric sacroiliitis.

Large, comma-shaped, paravertebral ossification may also be seen.

Other peripheral joints are less commonly involved.

Erosions & bony proliferation of the 1st to 4th MTP J with subluxation. Fluffy bony proliferation along the medial malleolus, navicular & sesamoid bones of the 1st metatarsal head. Ill-defined plantar calcaneal enthesophytes, periosteal reaction along the posterior aspect of the distal tibia , retrocalcaneal bursitis & thickening of the Achilles tendon ,& erosions at the subjacent calcaneus.

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