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Evaluation of the Hand Film


Radiographs of the hands are probably the most informative part of any screening series for arthritis. It is suggested that two views be obtained for evaluation: a posteroanterior (PA) view and a Nørgaard view of both hands and wrists (see Chapter 1 ). The former is excellent for imaging mineralization and soft tissue swelling; the latter is necessary for imaging early erosive changes. Using these two views, a systematic approach to observation should be employed. One must observe (1) the radiographic changes occurring in a specific joint and (2) the distribution of these changes within the hand and wrist to make an accurate diagnosis.

Radiographic changes

The radiographic changes occurring around a specific joint to be evaluated are soft tissue swelling, subluxation and dislocation, mineralization, calcification, joint space narrowing, erosion, and bone production. Each arthropathy has its own characteristic set of changes.

Soft Tissue Swelling

Symmetrical Swelling Around an Involved Joint ( Fig. 2-1 )

Symmetrical soft tissue swelling around a joint is a manifestation of synovitis. Soft tissue swelling is more readily appreciated with digital radiographic techniques than with film screen systems. Symmetrical swelling is most easily evaluated around the interphalangeal (IP) joints and wrist but can also be appreciated around the metacarpal phalangeal joint with careful evaluation. This type of swelling may be seen in any of the inflammatory arthropathies but is most common in rheumatoid arthritis.

Figure 2-1, AP radiograph ( A ), T1-weighted coronal ( B ) and fat-suppressed T2-weighted coronal MR image ( C ) demonstrate symmetrical soft-tissue swelling ( arrows ) around the third PIP joint.

Asymmetrical Swelling Around an Involved Joint ( Fig. 2-2 )

Asymmetrical swelling may not be actual soft tissue swelling, but rather soft tissue asymmetry due to subluxation or an osteophyte. The osteophyte may have a nonopaque cartilage cap that distorts the soft tissue. This swelling is seen in osteoarthritis and erosive osteoarthritis. Such swellings around the distal interphalangeal (DIP) joints are called Heberden nodes and around the proximal interphalangeal (PIP) joints are called Bouchard nodes.

Figure 2-2, Distortion of the soft tissue secondary to subluxation and osteophytes in the second and third PIP joints of a patient with osteoarthritis.

Diffuse Fusiform Swelling of an Entire Digit ( Fig. 2-3 )

This swollen digit is reminiscent of a sausage or a cocktail hot dog. This type of swelling is seen commonly in psoriatic and reactive arthritis when it involves the hands or feet. The cause of this pattern of soft tissue swelling is not clear but may be related to either enthesopathy or flexor tenosynovitis.

Figure 2-3, Swollen digit resembling a sausage in psoriatic arthritis.

Lumpy, Bumpy Soft Tissue Swelling ( Fig. 2-4 )

Lumpy soft tissue swelling is produced by infiltration with a substance foreign to the normal tissues around the joint (i.e., urate crystals, xanthomatous tissue, or amyloid). An eccentric bump may be observed near or away from the joint. Such a swelling is most commonly seen in gout and rarely in xanthomatous or amyloid disease. Granulomatous involvement of the hand with sarcoid can also be associated with a soft tissue bump.

Figure 2-4, Soft tissue masses distributed asymmetrically around the proximal and distal interphalangeal joint of the second digit in patient with gout.

Subluxation

Subluxations may not be visualized on the PA view of the hands and wrists, because the technician will reduce any subluxation during positioning. Subluxations become apparent on the Nørgaard view, because the fingers are not supported in a fixed position. Subluxation is a prominent feature of rheumatoid arthritis and the arthritis of lupus. The proximal phalanges sublux in an ulnar and palmar direction in relationship to the adjacent metacarpals ( Fig. 2-5 ). One can distinguish the arthritis of lupus from rheumatoid arthritis in that erosive disease is not present in the former. Subluxations do occur in osteoarthritis. These are usually in a lateral direction, deviating either radially or ulnarly ( Fig. 2-6 ).

Figure 2-5, Subluxations of the proximal phalanges in an ulnar and palmar direction in relationship to the adjacent metacarpals in lupus arthritis. Ulnar subluxation of carpals.

Figure 2-6, Lateral subluxation of the middle phalanx in relationship to the proximal phalanx of the third digit in erosive osteoarthritis.

Mineralization

Overall mineralization is evaluated by observing the metacarpal shaft of the second or the third digit. The sum of the two cortices of the shaft should equal one half the width of the shaft in a normally mineralized digit ( Fig. 2-7 ). The degree of generalized osteoporosis can be accurately judged by the sum of the two cortices in relationship to the width of the shaft ( Fig. 2-8 ).

Figure 2-7, Shaft of the third metacarpal demonstrating normal mineralization. At the line drawn on the diaphysis, the sum of the two cortices equals half the width of the shaft.

Figure 2-8, Diffuse osteoporosis. At the line drawn on the diaphysis of the third metacarpal, the sum of the two cortices is clearly less than half of the width of the shaft.

Normal Mineralization (see Fig. 2-7 )

Normal mineralization is typical of every arthropathy except rheumatoid arthritis. The maintenance of normal mineralization helps to distinguish the “rheumatoid variants”—psoriasis, reactive arthritis, and ankylosing spondylitis—from rheumatoid arthritis. The crystalline arthropathies and the osteoarthropathies maintain normal mineralization.

Diffuse Osteoporosis (see Fig. 2-8 )

This change is associated only with rheumatoid arthritis. It is seen in the advanced stages of this disease. All other arthropathies tend to maintain normal mineralization. If one observes osteoporosis in a patient with another arthropathy, such as gout, then the generalized osteoporosis may be secondary to disuse, to medication or to the normal aging process. It should not be blamed primarily on the arthropathy.

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