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Ulnocarpal
Swelling
Swelling and erosion around
the distal end of the ulna and the ulnar styloid process are early manifestations
of rheumatoid arthritis and are related to abnormality of the prestyloid
recess of the radiocarpal compartment, the inferior radioulnar compartment,
and the extensor carpi ulnaris tendon and sheath.
Prestyloid
recess
The prestyloid recess of the
radiocarpal compartment is intimate with the ulnar styloid process and
may extend circumferentially around the process or contact only its undersurface.
A corrugated synovial pattern frequently is visualized in arthrograms of
the rheumatoid wrist, most prominently in the prestyloid recess of the
radiocarpal compartment, where the pattern may be associated with filling
of the adjacent lymphatic structures. The latter phenomenon probably reflects
locally increased permeability of the inflamed synovial membrane in conjunction
with lymphatic hyperplasia. Prominent congested synovial folds can obliterate
the small opening into the prestyloid recess of the radiocarpal compartment,
with the result that radiocarpal arthrography may fail to make this diverticulum
visible. The inflamed synovial tissue within the prestyloid recess is in
contact with, and may produce erosions of, the tip of the ulnar styloid
process. These erosions begin as focal radiolucent areas within the subchondral
bone. As erosion progresses, however, the ulnar styloid tip becomes increasingly
irregular.
Inferior
radioulnar compartment
Proliferative synovitis within
the inferior radioulnar compartment frequently is coincident with rheumatoid
arthritis and results in localized prominence of the soft tissue. Contrast
filling of this compartment through defects in the triangular fibrocartilage
has been noted in radiocarpal arthrograms of 70 per cent and 58 per cent
of patients with rheumatoid arthritis. The diseased synovium extends over
the radial and the palmar surfaces of the distal portion of the ulna and
the adjacent ulnar aspect of the distal end of the radius.
Extensor
carpi ulnaris tendon and sheath
Tendinitis and tenosynovitis
of the extensor carpi ulnaris tendon and its sheath represent the third
factor that contributes to abnormality of the distal ulna and the ulnar
styloid process. Proliferative synovitis within the sheath is visualized
easily in arthrograms of the wrist because of the frequent communication
of the sheath with the radiocarpal compartment. This synovitis results
in swelling of the soft tissue along the outer aspect of the ulnar head.
Subjacent resorption of bone and periostitis occur along the medial margin
of the distal ulna beneath the inflamed tendon and sheath. |
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Swelling
of MTP 1-5
Radiologic abnormalities of
the forefoot also are frequent in rheumatoid arthritis. Furthermore, these
abnormalities commonly are the initial manifestation of the disease, antedating
changes in the hand and the wrist. Earliest alterations appear at the metatarso-phalangeal
joints, particularly the fifth. With progression, one or more metatarso-phalangeal
joints are affected in a relatively symmetric fashion in both feet. At
these sites, changes predominate on the medial aspect of the metatarsal
head with the exception of that in the fifth digit, at which site soft
tissue swelling and subjacent osseous erosion on the lateral aspect of
the bone can be a very early and important finding of the disease |
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Swelling
of IP I of greater toe
Although significant cartilaginous
and osseous lesions are infrequent in the interphalangeal articulations
of the second to fifth digits, the interphalangeal joint of the great toe
is commonly and characteristically affected. The interphalangeal joint
of the great toe participates in the rheumatoid process, and radiographic
changes at this site can be detected in as many as 50 per cent of foot
radiographs. |