Collagen Vascular Diseases (Connective Tissue Diseases)

The collagen vascular diseases (connective tissue diseases) are a group of diseases that have multiple, varied systemic manifestations. Articular symptoms play a minor role in the total clinical picture and usually produce little in the way of radiographic change in the joint. Although each disease has distinct features, there is a tendency toward overlap among the diseases. The diseases to be discussed are systemic lupus erythematosus, scleroderma, dermatomyositis, polyarteritis nodosa, and mixed connective tissue disease.

Systemic lupus erythematosus

Systemic lupus erythematous (SLE) is the most common of the collagen vascular diseases. In this disease, articular symptoms are present in 75 to 90 percent of patients. The radiographic changes are:

1.
Soft tissue swelling
2.
Juxta-articular osteoporosis
3.
Subluxations and dislocations
4.
Absence of erosions
5.
Absence of joint space loss
6.
Calcification
7.
Osteonecrosis
8.
Bilateral and symmetrical distribution
9.
Distribution in hand and wrist, hip, knee, and shoulder

The radiographic changes divide into three different categories: (1) deforming nonerosive arthritis, (2) osteonecrosis, and (3) calcification of soft tissue.

Deforming Nonerosive Arthritis

A deforming nonerosive arthritis is seen most commonly in the hands and wrists ( Fig. 20-1 ). Early in the course of the disease, soft tissue swelling is seen, with eventual soft tissue atrophy. Juxta-articular osteoporosis is present that eventually becomes diffuse osteoporosis. When not distorted by subluxation or dislocation, the joint space appears preserved. Subluxation or dislocation without erosive disease is the hallmark of SLE. The subluxations are usually easily reducible.

Figure 20-1, Posteroanterior (PA) view of both hands in a patient with SLE. Osteoporosis is present. Severe subluxations of all joints are present. There is no evidence of erosive disease. This is the classical deforming nonerosive arthritis of lupus.

Deformities may not be detected on the routine PA radiograph in which the technician has carefully positioned the digits for optimum imaging; however, on the Nørgaard view, in which the fingers are not positioned rigidly, the subluxations become apparent ( Fig. 20-2 ). A similar deforming nonerosive arthritis may involve the knee or the shoulder, but it is more difficult to image radiographically.

Figure 20-2, A, PA view of the hand in a patient with SLE. Juxta-articular osteoporosis is present. There is minimal subluxation of the MCP and PIP joints of the index finger. B, View of the same hand in the Nørgaard position. The fingers have not been rigidly positioned by the technician; therefore, severe subluxations of the MCP joints become apparent.

Osteonecrosis

Osteonecrosis is said to occur in 6 to 40 percent of patients with SLE. Although most of these patients are on steroids, it is known that SLE causes osteonecrosis even in the absence of steroid treatment. The patient with SLE with a significant vasculitic component who is being treated with steroids is extremely prone to osteonecrosis. The femoral heads, the humeral heads, the femoral condyles, the tibial plateaus, and the tali are the most common sites of osteonecrosis in SLE ( Fig. 20-3 ); however, it has also been seen in the lunates, the scaphoids, and the metacarpal and metatarsal heads ( Fig. 20-4 ). It usually occurs bilaterally and asymmetrically.

Figure 20-4, AP view of MTP joints in a patient with lupus. There is osteonecrosis present in the heads of the second and third metatarsals ( arrows ).

The radiographic findings are those observed in osteonecrosis of any etiology. Dead bone does not change radiographically. The radiographic changes observed are those of repair. The initial bone loss or osteoporosis in the repair process may not be appreciated radiographically. The first radiographic change may be increased smudgy density, which represents either dead bone that appears dense in comparison to the surrounding osteoporosis or reparative bone ( Fig. 20-5 ). One may see a combination of osteoporosis and osteosclerosis. Advanced osteonecrosis is present when a subchondral lucency is seen ( Fig. 20-6 ). The lucency is created by vacuum introduced between a distracted subchondral fragment and the remaining femoral head. It represents impending collapse of the articular segment into the underlying bone, if it has not already occurred. Once the articular surface has been deformed, the actual joint undergoes secondary osteoarthritic changes.