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1 Department of Radiology, University of Washington, Box 354755, 4245 Roosevelt Way NE, Seattle, WA 98105.
Received March 4, 2005;
accepted after revision March 18, 2005.
Address correspondence to F. S. Chew
(fchew{at}u.washington.edu).
Abstract
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The educational objectives of this continuing medical education activity are for the reader to exercise, self-assess, and improve skills in diagnostic radiology with regard to the interpretation of radiographs, CT, and MRI of the hand and to improve understanding of the appropriate use of CT and MRI in evaluating lesions of the hand.
Conclusion
The conditions illustrated in this article include erosive osteoarthritis, sarcoidosis, metastatic calcification, and synovial sarcoma. This article is qualified by the American Board of Radiology (ABR) in meeting the criteria for self-assessment toward the purpose of fulfilling requirements in the ABR Maintenance of Certification.
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Self-Assessment Questions
| QUESTION 1 Which is your preferred diagnosis, and why?
QUESTION 2 Which key feature of rheumatoid arthritis is present?
QUESTION 3 Compare erosive osteoarthritis with idiopathic osteoarthritis involving the hands:
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Description of the Images
Both hands have abnormalities distributed in the distal interphalangeal
(DIP) joints and the first carpal-metacarpal (CMC) joints. In the DIP joints,
the abnormalities are characterized by diffuse loss of cartilage space and
osteophyte formation. The severity of involvement is relatively uniform among
the different fingers and hands. At the CMC joints, cartilage space narrowing
and osteophyte formation are present. The alignment of the bones is normal,
soft-tissue swelling is absent, and bone mineralization is normal. There are
no marginal erosions and there is no periosteal new bone formation.
Solution to Question 1
Erosive osteoarthritis is a form of idiopathic osteoarthritis that has a
clinically prominent element of synovitis in the hand. On radiographs, the
hand in erosive osteoarthritis shows the typical features and distribution of
idiopathic (nonerosive) osteoarthritis with the additional features of diffuse
cartilage space loss and subchondral erosions. The combination of cartilage
space loss, subchondral erosions, and osteophyte formation results in a
gull-wing appearance on posteroanterior (PA) radiographs, well demonstrated in
the case shown here. Option A is the best response.
The clinical presentation of idiopathic (nonerosive) osteoarthritis does not include a significant component of synovitis. A clinical presentation of synovitis, as suggested by swelling, edema, tenderness, and erythema, essentially eliminates the diagnosis of idiopathic osteoarthritis, regardless of the radiographic appearance. Osteoarthritis typically presents as a localized process with pain and functional impairment, but not with synovitis. Option B is not the best response.
Rheumatoid factors are antibodies directed against IgG fragments. Although rheumatoid factor is present in the majority of patients with rheumatoid arthritis, patients with other chronic inflammatory conditions may have rheumatoid factor, and people with no clinical illness also may have rheumatoid factor. The prevalence of rheumatoid factor in low titer in people without clinical disease increases with the age of the population studied. Approximately 80% of patients with rheumatoid arthritis will have rheumatoid factor, generally in high titers. The presence of rheumatoid factor alone is insufficient for a diagnosis of rheumatoid arthritis. Option C is not the best response.
Rheumatoid arthritis and osteoarthritis are both relatively common conditions, so their occurrence in the same patient should not be a rare event. However, one would expect features of both forms of arthritis to develop. If osteoarthritis develops in the hand following damage from previous rheumatoid arthritis, secondary degenerative changes should be expected in the distribution of joints damaged by rheumatoid arthritis. If rheumatoid arthritis develops in the hand following osteoarthritis, one would expect established changes of osteoarthritis in the typical distribution (DIP, proximal interphalangeal joint [PIP], first CMC) with superimposed inflammatory changes also in the typical distribution for rheumatoid arthritis (MCP, carpus, PIP). In this case, the distribution of disease does not fit rheumatoid arthritis. Option D is not the best response.
Solution to Question 2
The typical distribution of involvement of the hand in rheumatoid arthritis
is in the proximal hand and carpus, specifically the MCP and PIP joints of the
hand, and the CMC, intercarpal, and radial-carpal joints of the wrist. When
the DIP joints are involved, the MCP and PIP joints tend to be much more
severely involved. In established cases, involvement tends to be polyarticular
and bilaterally symmetric. In this case, the distribution of disease is
polyarticular and bilaterally symmetric, but it spares the PIP and MCP joints
while involving the DIP joints. The carpus is spared except for the first CMC
joint. Option A is not the best response.
Diffuse cartilage space loss in inflammatory arthritis results from enzymatic action mediated by synovial inflammation. Diffuse cartilage loss may be seen in both rheumatoid arthritis and in inflammatory osteoarthritis. Option B is the best response.
Osteophyte formation is a key feature of osteoarthritis and other forms of degenerative arthritis. Osteophyte formation does not occur in the hand in active rheumatoid arthritis; in quiescent rheumatoid arthritis, secondary degenerative changes may occur in joints previously damaged by rheumatoid arthritis. These secondary changes will include osteophyte formation and subchondral sclerosis, but will be found in the typical anatomic distribution of rheumatoid arthritis. Option C is not the best response.
Marginal erosions are a key feature of rheumatoid arthritis. Enzymatic action at the interface of inflammatory pannus with bone will result in focal osteolysis or acute erosions. Acute erosions occur early at the bare areas of bone where there is a normal gap between the articular cartilage and the periosteum. Marginal erosions are not present in this case. Option D is not the best response.
Solution to Question 3
Idiopathic osteoarthritis affects men and women in roughly equal numbers;
the prevalence increases with age. Erosive osteoarthritis has a strong female
predominance (12:1) and the typical patient is a postmenopausal woman.
Option A is not the best response.
The anatomic distribution of involvement in primary osteoarthritis and erosive osteoarthritis is the same: DIP, PIP, and first CMC joints, generally with sparing of the other joints of the hand and wrist. This pattern of distribution is characteristic and, in well-established disease, differentiates osteoarthritis from inflammatory forms of arthritis such as rheumatoid arthritis, psoriatic arthritis," and septic arthritis and from crystal-mediated forms of arthritis such as pyrophosphate arthropathy and gouty arthritis. Option B is the best response.
The inflammation in erosive osteoarthritis usually subsides within a few months to a couple of years, leaving residual degenerative changes [1]. Although joint degeneration always has some component of synovial inflammation because of the presence of joint debris and cartilage breakdown products, inflammation is not clinically significant in idiopathic osteoarthritis. Option C is not the best response.
Erosive osteoarthritis has a characteristic gull-wing appearance that may be seen on PA radiographs at the interphalangeal (IP) joints of the fingers, corresponding to central erosions and bone hypertrophy [2]. This appearance also may be seen in idiopathic osteoarthritis and will persist in erosive osteoarthritis after resolution of the inflammatory process. Option D is not the best response.
Conclusion
The actual diagnosis in this case is erosive (inflammatory) osteoarthritis.
The radiologic diagnosis hinges on three observations: (1) the
characterization of the abnormalities as degenerative, but with diffuse
cartilage space loss and subchondral erosions; (2) the distribution of
involvement in the DIP and first CMC joints; and (3) the absence of marginal
erosions, fusiform soft-tissue swelling, or osteopenia. In the setting of
polyarticular inflammatory joint disease in the hand, the diagnosis of erosive
osteoarthritis can be made. If these radiographs were combined with a clinical
presentation of pain and functional loss without inflammatory features, then
the diagnosis of primary osteoarthritis would be appropriate. If the clinical
presentation had been the recent onset of inflammatory polyarthritis involving
the PIP, MCP, and/or carpal joints and the rheumatoid factor were positive in
high titer, then the diagnosis of new-onset rheumatoid arthritis superimposed
on preexisting osteoarthritis should be considered.
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Self-Assessment Questions
| QUESTION 1 How does the morphology of the soft-tissue swelling refine the differential diagnosis?
QUESTION 2 How do the bone abnormalities present in this case refine the differential diagnosis?
QUESTION 3 Regarding the differential diagnosis in this case, which statement is most likely to be FALSE?
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Solution to Question 1
The term sausage-digit is used to describe soft-tissue swelling that
involves an entire digit uniformly, so that the digit resembles a sausage. In
this case, the digits most involved, the left ring finger and the right index
finger, show soft-tissue swelling that involves the proximal portions but not
the distal portions. When present, sausage-digit soft-tissue swelling is
associated with psoriatic arthritis. Option A is not the best
response.
Fusiform soft-tissue swelling that is centered around a joint is characteristic of inflammatory arthritis, particularly rheumatoid arthritis. Fusiform soft-tissue swelling represents joint effusion and synovial inflammation and hypertrophy, and should therefore be centered at a joint. In this case, while somewhat fusiform in morphology, the soft-tissue swelling is centered more over the shafts of the phalanges than the joints. Option B is not the best response.
Lumpy-bumpy soft-tissue swelling describes asymmetric, lobulated swelling and, if present, would strongly suggest the diagnosis of tophaceous gout. If chronic erosions with overhanging edges are seen in association with lumpy-bumpy soft-tissue swelling, the appearance would be pathognomonic. In this case, the soft-tissue swelling is relatively symmetric around the involved digits. Option C is not the best response.
Infections that involve both bone and soft tissue are common. Other conditions in adition to infection that commonly involve both bone and soft tissue include trauma, hemangioma, sarcoidosis, tophaceous gout, and neoplasms. Option D is the best response.
Solution to Question 2
If present, bone abnormalities with equal involvement on both sides of a
joint would suggest an articular process. However, this case does not show
bone abnormalities on both sides of any of the joints. Option A is not the
best response.
Endosteal thinning of the cortex is an indication of an enlarging mass within the medullary cavity. The endosteal aspect of the cortex remodels in response to enlargement of the mass. In the hand, the most common underlying lesion is an enchondroma. Option B is the best response.
Periosteal bone formation is not evident in this case. When present, periosteal bone formation may suggest response to infection or other inflammatory conditions, response to rapidly enlarging mass lesions such as malignant tumors, or response to systemic conditions as in hypertrophic osteoarthropathy. Option C is not the best response.
Regional hyperemia results in acute osteoporosis. Bone resorption is greatest in the parts that have the most abundant blood supply, the subchondral bone. In this case, the subchondral bone is not involved to a greater degree than other portions of the trabecular bone. Option D is not the best response.
Solution to Question 3
Enchondromas are benign tumors of hyaline cartilage that are found within
bone. They may expand the cortex as they enlarge, but they should not breach
the cortex and extend into the soft tissues; if they do, sarcomatous
degeneration to chondrosarcoma is likely. Therefore, the presence of
soft-tissue swelling is a reasonable basis for eliminating enchondromatosis as
a diagnostic possibility. Option A is not the best response.
Infections of the hand may be caused by a variety of different organisms. Pyogenic bacteria tend to cause osteolysis, sometimes with the formation of involucrum and sequestrum. The involucrum is formed by periosteal reaction that surrounds the infection, and sequestrum is devitalized bone. Involucrum is commonly seen in children, where the periosteum is strong enough to present a barrier to the spread of infection, but not in adults, where it is not. Organisms such as tuberculosis or fungus typically do not evoke reactive bone formation. The lack of periosteal bone reaction is therefore not a compelling reason to exclude infection as a diagnostic possibility. Option B is not the best response.
Tophaceous gout is the result of long-standing hyperuricemia. Urate crystals become deposited in the soft tissues in and around joints in a more or less random fashion. The resulting appearance in the soft tissues of the hand is a lumpy-bumpy appearance, not a symmetric one. Therefore, the symmetry of the soft-tissue swelling can be used to eliminate tophaceous gout from consideration. Option C is not the best response.
Metastatic disease to the hand is relatively rare; multifocal metastatic disease in the hand is rarer still. Most skeletal metastases are found in the axial skeleton (skull, spine, ribs, and pelvis) and in the proximal humeri and femurs. The only primary site whose cancers metastasize to the hands with any frequency is the lung. Metastases from lung carcinoma are typically lytic, occasionally mixed lytic and blastic, and rarely blastic. Therefore, the lack of sclerosis is not a compelling reason not to consider metastatic disease in the differential diagnosis of multiple lytic lesions. Option D is the best response.
Conclusion
The diagnosis in this case is sarcoidosis with involvement of the hands.
The chest radiograph showed bilateral hilar adenopathy; this information was
withheld for the sake of discussion. Sarcoidosis may involve the joints in
about 10% of cases, but sarcoidosis most often causes transient migratory
polyarticular arthralgias without radiographic findings. A chronic
granulomatous arthritis develops in only a few, leading to chronic
noncaseating granulomatous inflammation of the synovium. Granulomas within or
adjacent to the bone may result in punched-out cortical erosions or central
lytic lesions with non-aggressive features within the medullary cavity. The
process does not appear to provoke reactive bone, and the remaining portions
of cortex and trabeculae become reinforced and thickened. The middle and
distal phalanges of the fingers are the typical sites of involvement. The
characteristic appearance caused by the presence of multiple granulomatous
lesions has been described as lacelike, latticework, or honeycomb
(Fig. 2C). The most common
sites of involvement in the musculoskeletal system are the hands and feet
[3]. Cyst-like lesions in bone
are, in fact, bone that has been replaced by solid sarcoid granulomas and are
not actually cysts. Soft-tissue involvement by sarcoid may occur in one-third
of patients. The hand, bone, muscle, tendon, cutaneous or subcutaneous tissue,
or synovium may be involved [4,
5]. Enlargement of the
fingertips may result in an appearance on physical examination described as
"pseudoclubbing" and reflects phalangeal involvement
[6]. The natural history of
sarcoid bone lesions is variable, ranging from rare cases of recovery to
gradual progression and eventual autoamputation. Treatment with systemic
corticosteroids may result in improvement or stabilization of bone lesions,
but the bone usually will not return to normal.
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Self-Assessment Questions
| QUESTION 1 Which of the following is most likely to be an advantage of the CT scan over an MRI scan in evaluating these lesions?
QUESTION 2 Which statement is most likely to be TRUE regarding the calcifications?
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Solution to Question 1
In the anatomic staging of primary soft-tissue musculoskeletal sarcomas,
MRI and CT have been shown to be equally accurate
[7]. Although it is unlikely
that a study of similar power comparing MRI and CT in benign lesions will ever
be performed, it generally is accepted that these techniques are essentially
equivalent for showing anatomy in the axial plane. Depending on the technical
parameters, the delineation of anatomic structures on reformatted CT images in
other anatomic planes may not be as good as in the original axial plane. The
quality of anatomic delineation on MRI typically is independent of the imaging
plane chosen. Option A is not the best response.
Characterization of mass lesions on CT is based on differences in the attenuation of incident X-rays, not on whether the mass is cystic or solid. Many masses that have the same X-ray attenuation as water are in fact fluid filled and cystic, so that sometimes a distinction between cystic and solid can be made. However, masses with attenuation similar to solid organs and muscle also may be cystic. Fluid-sensitive MRI pulse sequences are more reliable in detecting fluid than CT. Option B is not the best response.
The ability to show the vascular supply of a lesion depends on identifying the actual feeding vessels. Neither technique is very good at identifying the vascular supply of small lesions. Because of its multiplanar capability, one might suppose that MRI would be better than CT, but there is little if any supporting evidence. Option C is not the best response.
CT is an excellent technique for detecting and characterizing calcifications, because the X-ray attenuation of calcium atoms is very different from the other non-trace elements that make up the structure of the human body. MRI is much less accurate in detecting and displaying calcified tissue [8]. Option D is the best response.
Solution to Question 2
The presence of a cortical and trabecular structure is indicative of bone;
if the bone were located in the soft tissues, it would be heterotopic.
However, there is no cortical or trabecular structure in this case. Option
A is not the best response.
Some of the calcifications do have a gradient that is denser in the dependent portion. This is seen best in the 5 o'clock position of the axial CT image. Aqueous suspensions of calcium will settle out dependently, given sufficient time. A density gradient is unlikely to be visible on radiographs because their visualization would require a horizontal X-ray beam; hand radiographs are typically obtained with a vertical beam. Option B is the best response.
Cartilage tends to have a lobular morphology. Calcification of cartilage tends to occur around the periphery of individual lobules, often resulting in an appearance that resembles rings and arcs. Although the calcified lesions in this case could be described as having a lobular morphology, the calcification is distributed within the lesions, and not just around the periphery. Option C is not the best response.
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Conclusion
The diagnosis in this case is metastatic calcification secondary to
long-standing hemodialysis for chronic renal failure. Even without the
clinical history, the two vascular clips near the expected location of the
radial artery are clues to the presence of a hemodialysis shunt, suggesting
the diagnosis. The development of these multilocular cystic calcium deposits
is thought to be related to the composition of the dialysate, and changing the
composition of the dialysate may result in rapid diminution or even full
resolution of the deposits
[10]. In this case, treatment
resulted in rapid improvement (Fig.
3D). Because the calcium is in the form of an aqueous suspension
(milk of calcium), fluid-sedimentation gradients and levels may be seen on CT
or horizontal beam radiographs. Mass effect, such as compression of
neurovascular structures, may lead to symptoms. Other manifestations in the
hand of hemodialysis for chronic renal failure include sclerotic changes in
the bones, osteoarthropathy, secondary hyperparathyroidism, and amyloidosis.
The radiographic appearance of metastatic calcification secondary to
hemodialysis may be identical to that of tumoral calcinosis, a condition
characterized by massive, lobulated, periarticular calcium deposits and caused
by heritable metabolic dysfunction in phosphate regulation.
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Self-Assessment Questions
| QUESTION 1 What recommendation would you make regarding the use of IV gadolinium for this MRI examination, and why?
QUESTION 2 Which is your preferred diagnosis, and why?
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Solution to Question 1
Gadolinium is not a reliable method for distinguishing benign lesions from
malignant lesions in the musculoskeletal system, as both benign and malignant
lesions may or may not show enhancement
[11].
Gadolinium may help distinguish cystic lesions from solid lesions. Gadolinium initially is distributed to tissues through the vascular system but rapidly diffuses into the extracellular space. Cystic lesions may initially show rim enhancement, but as the gadolinium diffuses centrally, the rim of enhancement will grow thicker over time, a process that occurs over minutes. Solid lesions that are vascularized will show internal enhancement, as in this case, rather than rim enhancement.
Gadolinium-enhanced MRI has been shown in general to be better than nonenhanced MRI for detection and characterization of soft-tissue musculoskeletal masses and for anatomic staging and treatment planning [12]. These general findings are supported by the literature on tumors of the hand and wrist [13].
Gadolinium does add cost to an MRI examination, approximately hundreds of dollars. In the United States, cost per se generally is an insufficient justification for not using gadolinium. The possible benefits of gadolinium should be balanced against the cost and risk to the patient.
Solution to Question 2
Ganglion cysts are most commonly found on the dorsal aspect of the wrist,
and next most commonly on the volar aspect of the wrist. The other common
location is in proximity to the flexor tendon sheath of the fingers, on the
volar aspect, often in association with the A1 pulley. Other locations are
possible but much less common. In this case, the lesion is lateral to the
third metacarpal head, not a common location for a ganglion cyst. Option A
is not the best response.
Intramuscular myxomas are a heterogeneous group of benign soft-tissue lesions that contain abundant myxoid ground substance. The myxoid material is composed of mucopolysaccharides, and the lesions have a homogeneous signal that is hypointense to muscle on T1-weighted MRI and hyperintense on T2-weighted images. This pattern of signal intensity is non-specific and does not distinguish myxoma from other soft-tissue lesions. Option B is not the best response.
Cystic soft-tissue lesions exhibit rim enhancement on MRI following gadolinium infusion, unless they are vascular. Vascular lesions generally will enhance to the same extent as blood vessels. Solid lesions may enhance uniformly, heterogeneously, or not at all. In this case, there is uniform enhancement of the entire lesion, less intense than the adjacent vessels, indicating a solid tumor. Option C is the best response.
Glomus tumors of the hand classically present with cold hypersensitivity, paroxysmal pain, and pinpoint pain. The lesion itself may be painful or tender. Most glomus tumors of the hand are located in the fingertips. In this case, the clinical presentation included none of the features of glomus tumors. Option D is not the best response.
Conclusion
The diagnosis in this case is synovial sarcoma. Primary musculoskeletal
sarcomas involving the soft tissues of the hand are rare, but it is important
for the radiologist to maintain an awareness that they do occur. The entire
range of musculoskeletal sarcomas have been described in the hand, including
synovial sarcoma, liposarcoma, fibrosarcoma, malignant fibrous histiocytoma
(MFH), malignant peripheral nerve sheath tumors, rhabdomyosarcoma, and clear
cell sarcoma. The most common primary malignancy of the musculoskeletal soft
tissues is MFH, but in the young adult, synovial sarcoma is more common. The
MRI features of these lesions are not specific
[14], and although synovial
sarcomas are more likely to calcify than other sarcomas, calcification is
difficult to recognize on MRI. The age of peak incidence is between 20 to 49
years. Synovial sarcomas are slow-growing lesions, but local recurrence and
metastases may occur. Treatment is by wide surgical resection.
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