Radiographic Findings
• Hand and foot have earliest
involvement; watch for subtle changes
• Focal soft tissue swelling
may be clue to underlying bone involvement
○ Especially about MCP, PIP,
ulnar styloid
• Osteoporosis
○ Early: Juxtaarticular
○ Later: Diffuse
• Erosions
○ Earliest pattern is loss of
cortical distinctness, followed by dot-dash pattern of cortical loss
○ Marginal erosions tend to be
early in portion of bone, which is within capsule but not covered by cartilage
– Mouse ears appearance at
base of phalanges
– Ulnar and radial styloid
processes
○ Direct subchondral erosions
○ Late severe destruction of
osseous structures
– May give pencil-in-cup
appearance in phalanges
– May destroy distal ulna or
proximal carpal row
• Cartilage destruction
○ Initial radiographs may make
joint space appear wide due to distension from effusion
○ Cartilage thinning and
narrowing of joint are uniform
• Subchondral cysts frequent finding in RA but nonspecific
• Ulnar styloid may show
capping: Only site of productive change
in RA
• Malalignment due to ligament/tendon disruption
○ Carpus
– Ulnar translocation (carpals
subluxate ulnarly such that lunate mostly articulates with ulna)
– Volar subluxation of carpus
on radius
– Scapholunate dissociation
– Volar or dorsal intercalated
segmental instability (VISI or DISI)
○ Digits
– Ulnar drift at MCPs
– Volar subluxation of MCPs
– Hitchhiker's thumb
– "Boutonnière"
(hyperflexion PIP, hyperextension DIP) and "swan neck"
(hyperextension PIP, hyperflexion DIP) deformities
CT Findings
• Mirror radiographic
findings; rarely used except in postoperative evaluation
MR Findings
• T1WI
○ Low signal effusion,
erosions
• Fluid-sensitive sequences
○ High signal effusion,
erosions, subchondral cysts
○ High signal tenosynovitis
○ Pannus: Thick, nodular, low
signal synovium outlined by effusion
○ Marrow edema: Subchondral
high signal
• T1WI C+ FS
○ Thickened, avidly enhancing
synovium outlines low signal effusion and erosions
○ Tenosynovitis: Enhancement
of involved tendons
○ Median nerve may enhance if
impinged by tenosynovitis
in
carpal tunnel
Ultrasonographic Findings
• Excellent for early
effusions in small joints
• Tenosynovitis: Hyperechoic
• Tendon rupture: Direct
visualization
• Color Doppler evaluates
hypervascularity
• Rheumatoid nodule:
Homogeneous hypoechoic mass
Imaging Recommendations
• Best imaging tool
○ Initial imaging is
radiograph
○ If negative, US or MR useful
to detect early disease
– Excellent for detection, but
not prognostic for individual
○ Following therapy (generally
drug studies)
– US with Doppler good for
effusions, inflammation
– MR best for following early
erosions
• Protocol advice
○ Radiographs: PA and
open-book view (Norgard)
– Open-book view helpful to
identify early MCP, triquetral, and pisiform erosions
– If carpal alignment evaluation
is required, true lateral view should be added
○ Half dose contrast at 3T MR
sufficient for assessing synovitis/tenosynovitis in early RA
CLINICAL ISSUES
• RA in 1% of worldwide
population
○ 5% in some Native American
populations
• Female > male (3:1)
• Carpus involved in 80%
patients with RA
• MCPs involved in 85% patients
with RA
• Hand PIP involved in 75%
patients with RA
DIAGNOSTIC CHECKLIST
• Earliest RA may be
monostotic or asymmetric
○ Must differentiate from
septic joint
• Use sites of focal soft
tissue swelling to guide you to subtle osseous findings on radiograph
• Watch for cortical
indistinctness and dot-dash pattern for earliest radiographic signs of erosion
(A)
is normal, with intact cortex, cartilage, bone density, and capsule.
(B)
shows early disease, with only synovitis and effusion.
(C)
shows juxtaarticular osteopenia, with cortex becoming indistinct, the dotdash pattern.
(D)
shows thinning of cartilage and marginal erosions in the portion of bone which
is intracapsular but not protected by cartilage.
(E)
shows progression of osteopenia and subchondral erosions extending through
cartilage defects.
(F)
shows arthritis mutilans, with pencil-in-cup deformity, seen in end-stage
disease.
Longitudinal color Doppler ultrasound shows typical tenosynovitis with marked increase in vascularity, indicating hyperemia . There is also synovial thickening and hyperemia of the palmar aspect of the joint capsule , indicating joint synovitis. This proved to be early RA, normal on radiograph.
Axial T2WI FS MR shows high signal tenosynovitis surrounding normal extensor and flexor tendons and synovitis in
the DRUJ . There are no erosions; radiograph was normal.
Coronal T1WI MR, obtained in a patient with a new
onset of unilateral joint pain and swelling, shows the MC heads with marginal erosions
. These erosions were not visible on radiograph.
Coronal T2WI FS MR in the same patient shows
involvement beyond the MCPs. The carpal bones, radiocarpal joint, and DRUJ show
similar findings of effusion and both marginal and subchondral erosions. The distribution
and pattern of erosive disease is typical of RA.
PA radiograph in a patient with new-onset hand pain and swelling shows swelling at the MCPs and PIPs .There is no focal osteoporosis or erosion, but distension of MCPs 2 and 3 is seen . This is due to synovitis and effusion, very early radiographic signs of RA.
PA radiograph shows juxtaarticular osteopenia and
cartilage narrowing at the MCPs ſt. Cortical indistinctness on the MC heads is the dot-dash
pattern, indicating early erosive change.
PA radiograph shows a typical case of marginal erosions
in RA . These are seen early in the erosive process, occurring in bone that is
intracapsular but not protected by cartilage. This is the region of bone that
is most vulnerable to the inflammatory process.
PA radiograph in a patient with early RA shows
that the bone density is normal. The only involved joint is a PIP , showing erosion and severe cartilage damage. Remember that
early erosions in RA are as likely to involve the PIP as the MCP.
PA radiograph shows a nodule , which causes scalloping of underlying bone . Note the decreased cartilage width at the 2nd MCP, along with the marginal erosion of the MC head . The appearance and distribution is typical for RA with a rheumatoid nodule.
PA radiograph in a 48- year-old man shows severe rapid-onset
osteopenia in a band-like pattern of the distal radius as well as soft tissue swelling and likely erosion at the ulnar
styloid .
Coronal T1 MR arthrogram of the same patient
shows edema and erosions of the ulnar styloid and triquetrum . In addition, there is disruption of the scapholunate ligament .
Coronal T2 FS MR in the same patient confirms the
erosions in the ulnar styloid, triquetrum, and demonstrates another in the
scaphoid . Note the mild thinning of
cartilage at the radioscaphoid joint , with other cartilage appearing
normal. This patient's erosions are more extensive than suspected on radiograph.
PA radiograph shows normal bone density and only a
single MCP with soft tissue swelling and single associated erosion . This is the only
radiographic sign of RA in this young woman.
PA radiograph in a patient with early RA shows radiocarpal
joint narrowing, as well as ulnar translation of the entire carpus . Note that the majority of the lunate overlies the ulna,
confirming that translation.
PA radiograph in a middle-aged man with joint pain
shows only soft tissue swelling near the ulnar styloid. This should suggest early
RA.
In the same patient, an indirect T2 C+ FS MR
arthrogram shows ulnar sided tenosynovitis and small ulnar styloid erosion with extensive edema. There is also scapholunate ligament disruption
.
Axial PD C+ FS MR in the same patient, through
the distal carpus, shows more extensive erosion of the distal ulna than was suspected on the coronal.
PA radiograph demonstrates severe osteopenia with
arthritis mutilans. The erosions are so severe that "pencil-in-cup"
morphology is seen in multiple joints . Although arthritis mutilans is a hallmark for psoriatic arthritis,
it is also seen in any severe inflammatory arthropathy, including RA.