Septic Arthritis: A Complication of Rheumatoid Arthritis 1



Diagnostic Radiology

Martin I. Gelman, M.D., and John R. Ward, M.D. Eighteen cases of long-standing rheumatoid arthritis and superimposed pyarthrosis were reviewed to determine the most distinguishing radiographic features. Soft-tissue changes allowed earlier diagnosis in the knee and ankle joints and consisted of large asymmetrical joint effusion and fat-pad edema. Bony articular changes were more helpful than soft-tissue changes in the wrist and hip because of the paucity of adjacent extracapsular fat and were associated with delayed radiographic recognition of superimposed pyarthrosis. These changes are presumptive evidence of complicating septic arthritis and their presence necessitates needle aspiration and culture of the joint for proper definitive treatment. INDEX TERMS:

Arthritis, rheumatoid • Joints, diseases • (Multiple joints, septic arthritis

4[8].260)e (Multiple joints, rheumatoid arthritis, unusual manifestation 4[8].712) Radiology 122:17-23, January 1977

already present in the rheumatoid patient (8, 9, 13). Thus radiographs have largely been used to assess the response to treatment in terms of evaluating progression of changes as the result of infection. The present study was undertaken to determine the radiographic changes seen in bacterial arthritis complicating rheumatoid arthritis, and to describe those findings which are most reliable in suggesting its presence.

ARTHRITIS patients are at greater risk to septic arthritis than are those with the nonrheumatoid type (2). Early recognition is difficult because of active inflammation in the joints secondary to rheumatoid arthritis as well as suppression of the usual signs and symptoms of infection by the drugs used for treatment. Early diagnosis and treatment of acute bacterial arthritis, however, is essential since further joint destruction may result. While the clinician may do arthrocentesis for culture as well as other diagnostic studies in the patient who has an acute flare in one or more joints, the diagnosis is often overlooked. Radiologic examination has not been considered useful in assessing the presence of early infection in rheumatoid arthritis because of the soft tissue swelling, periarticular deossification and articular erosions usually HEUMATOlD

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MATERIALS AND METHODS

Eighteen patients with documented rheumatoid arthritis complicated by septic arthritis were admitted to the University of Utah Hospital and Salt Lake City L.D.S. Hospital from 1966 through 1975. The diagnosis of septic arthritis

Fig. 1, A. Radiograph of normal knee with preserved infrapatellar fat pad. B. Line drawing of Fig. 1, A. 1 From the Department of Radiology, University of Utah Medical Center, Salt Lake City, Utah. Presented at the Sixty-first Scientific Assembly and Annual Meeting of the Radiological Society of North America, Chicago, 111., Nov. 3D-Dec. 5, 1975. shan

17

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Age, Sex

Patient

Table I:

Wrist

vrs.

40 yrs.

12 yrs. 5 yrs.

13 yrs.

9 yrs.

20 yrs. Undetermined 5 yrs.

Many years

3 yrs.

Knee

Great toe Knee

Knee

Ankle

Elbow Shoulder Wrist

Knee

Elbow

Hip

Knee

11 yrs.

5 yrs.

Hip

10 yrs.

25

Knee

Ankle

Joint

20 yrs.

27 yrs.

Duration of Rheumatoid Arthritis

10 days

2 days 4 days

14 days

4 days

2 mos. 3 days 1 mo.

1 wk.

1 mo.

6 mos.

1 wk.

7 mos.

2 days

4 wks.

2 mos.

Duration of Symptoms Before Diagnosis

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+

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a

a

+

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+

0

+

0

+

0

0 +

0

0 +

+

a a

+

a

+

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a a

0

+

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Initial Radiographic Changes Soft Bony Tissue Septic Changes Changes Edema of retrotibial fat pad Large suprapatellar effusion, edema of infrapatellar fat pad Progressive artieular destruction of carpal bones over I-year interval Progressive articular destruction Large suprapatellar effusion, edema of infrapatellar fat pad Edema of fat pad adjacent to hip capsule, proqressive articular destruction Marked soft-tissue swelling Large suprapatellar effusion, edema of infrapatellar fat pad Rheumatoid None Bulging of wrist capsule, interval increased; deossification and joint space narrowing Edema of retrotibial fat pad Large suprapatellar effusion, edema of infrapatellar fat pad, proqressive articular destruction Soft-tissue swelling Large suprapatellar effusion, edema of infrapatellar f at pad, proq ressive articular destruction Large suprapatellar effusion, edema of infrapatellar fat pad

Soft Tissue and/or Bony Changes

0

0 0

0

0

a

a a

Staphylococcus

Staphylococcus Staphylococcus

a a

+

Staphylococcus

Staphylococcus

Streptococcus Streptococcus Streptococcus

Proteus

+

+

0 +

a

a

Salmonella

Staphylococcus

a

Staphylococcus

Staphylococcus

Staphylococcus

Staphylococcus

+

a

Organism No growth*

a a

0

a a

0

+

a

+

0

+

0

Steroids Intrasvsarticular temic

Correlation of Clinical, Radiographic and Bacteriologic Data of Rheumatoid Joints with Complicating Septic Arthritis

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SEPTIC ARTHRITIS

Vol. 122

was established in 17 patients by culture of the synovial fluid. The duration of rheumatoid arthritis ranged from 3 to 40 years. Six patients were women and 12 were men ranging in age from 36 to 68 years. Most of the patients had moderately severe to severe involvement of multiple joints by rheumatoid arthritis. Three patients had recent intraarticular steroid injections prior to the onset of sepsis while 7 patients were receiving oral corticosteroids at the time of onset of joint sepsis. Fifteen patients with 17 involved joints had radiographs which were used in this evaluation. Nine patients had clinical symptoms of septic arthritis for 14 days or less, 3 for 15-28 days and 5 for longer than one month (TABLE

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All of the patients presented with pain in the involved joint. On physical examination, tenderness and marked decrease in range of motion were present. Swelling was usually noted in the septic joints whereas increased heat and redness were less common features. The white blood cell count was most commonly normal or only slightly elevated; however, there was frequently a polymorphonuclear leukocytosis with a shift to the left. Five patients had sepsis involving more than one joint. The knee was involved in nine instances, the elbow in seven, the wrist in four, the ankle in three and the hip and great toe in two each. Although the source of infection was frequently not definitely established, the most probable predisposing factors in 10 cases were: skin infection, 2; prior surgical drainage of skin infection, 2; stasis ulcer, 1; gangrene of foot, 1; pneumonia, 1; infected surgical wound, 1; decubitus ulcer, 1; and previous bone graft, 1. The aspirated joint fluid was often purulent with nucleated cell counts greater than 100,000 cells/rnm'' and greater than 90% polymorphonuclear leukocytes. On culture, the infecting organism was Staphylococcus aureus, coagulase positive in 11 patients, beta hemolytic streptococcus in 3 and salmonella, Proteus morqenti and pneumococcus in 1 patient each. In our series, the knee and elbow were the most frequent joints involved and the infection was most commonly monarticular in contrast to polyarticular involvement in at least half of the reported cases (7, 11). Soft-tissue changes alone consisting of large joint effusion, adjacent soft-tissue swelling or fat pad edema were observed on the initial radiographic studies of 13 of the 17 joints. These changes were particularly useful with respect to the knee joint where the infrapatellar fat pad is well visualized in the normal knee (Fig. 1). This fat pad is extrasynovial but intracapsular in location and, although it is not affected by a simple joint effusion, a pyogenic arthritis would provide sufficient inflammatory reaction to cause edema. This is manifested by indistinctness of the interface between the anterior aspect of the joint space and infrapatellar fat pad, (Fig. 2, A), partial obliteration of the fat pad (Fig. 2, B), or coarse septa within the fat pad (Fig. 2, C) (4). In cases involving the ankle, soft-tissue swelling was observed

20

MARTIN

I. GELMAN AND JOHN R. WARD

January 1977

Fig. 2. A, Band C. Three different rheumatoid knees with superimposed septic arthritis. Note suprapatellar effusion and edema of infrapatellar fat pad demonstrated by indistinctness of the anterior joint space-fat pad interface (2, A), obliteration of the superior aspect of the fat pad (2, B) or coarse septa within the fat pad (2, C).

posteriorly behind the tibia in the region of the retrotibial fat pad which is outside of the normal anatomical boundary of the joint capsule (Fig. 3). In the absence of trauma and

in the presence of asymmetrical soft-tissue changes in a patient with rheumatoid arthritis, these findings should alert the radiologist to the possibility of sepsis (Fig. 4). In 2 pa-

Fig. 3. A. Radiograph of normal ankle with preserved retrotibial fat pad. B. Line drawing of Fig. 3, A.

SEPTIC ARTHRITIS

Vol. 122

tients with elbow involvement, marked soft-tissue swelling with extension some distance from the normal anatomical confines of the joint was appreciated in only one case without delineation of bowed anterior and posterior fat pads. In the two wrists, asymmetrical capsular distension and indistinctness of the navicular fat stripe was appreciated in one case with associated marked interval deossification and rapid joint-space narrowing (Fig. 5). No soft-tissue changes were appreciated in the shoulder involved in our series. Asymmetrical indistinctness of the joint capsule was observed in 1 of the 2 cases of hip pyarthrosis with accompanying rapid unilateral joint destruction (Fig. 6). Bony articular changes were observed initially in 5 of the 17 joints radiographed. These changes most commonly included progressive bony articular destruction and, to a lesser degree, progressive deossification and joint-space narrowing and were most helpful with respect to the wrist and hip joints. The observation of rapid destruction of joint surfaces disproportionate to other joints involved by rheumatoid arthritis and considerable asymmetry of involvement when compared to the corresponding joint of the opposite side has been valuable in detecting superimposed pyarthrosis (Fig. 7). DISCUSSION

The incidence of septic arthritis among all rheumatoid arthritis patients ranges from less than 1 % to 12 % (1, 5). The patient with rheumatoid arthritis may be predisposed to joint infection because of the chronicity and debilitation of the illness as well as the possible effects of systemic

21

Diagnostic Radiology

Fig. 4. Septic rheumatoid ankle with early edema of retrotibial fat pad.

steroids (13). Systemic steroids, however, do not constitute a common predisposing factor since they were not administered to most of the patients in our series. Several investigators have shown (on the basis of synovial fluid studies) decreased phagocytosis as well as bacteriolytic and bactericidal activity of leukocytes in patients with rheumatoid arthritis which may account for increased susceptibility to intra-articular infection (3, 10). Although

Fig. 5. A. Rheumatoid wrist with superimposed septic arthritis. Asymmetrical capsular distension of the wrist joint associated with marked interval asymmetrical deossification and rapid joint space narrowing indicates pyarthrosis superimposed on rheumatoid arthritis. Note bulging of navicular fat stripe (secondary to capsular distension) as well as fuzziness of interface (arrows) when compared with the opposite wrist. B. Opposite wrist.

22

MARTIN

I. GELMAN AND JOHN R. WARD

January 1977

Fig. 6. A. Narrowing of supero-medial aspect of hip joint space secondary to rheumatoid arthritis. The capsular shadow is well visualized (arrows). B. One week later, asymmetrical indistinctness of the hip capsule due to edema of the extracapsular fat is observed (arrows) in association with rapid progressive monarticular destruction. These findings indicate complicating septic arthritis.

the basic cause of this complication is not fully understood, infection constitutes the most common cause of death in rheumatoid patients (2). The literature cites a mortality rate as high as 35 % in patients with suppurative arthritis complicating rheumatoid arthritis (6, 7). This figure does not agree with our series in which only one patient died from this complication. The important point, however, is that early detection becomes mandatory if full recovery is to be achieved. In the radiologic recognition of early septic arthritis complicating rheumatoid arthritis, the question arises as to the ability of rheumatoid arthritis to produce the same soft-tissue changes since inflammation is a part of this process as well. Edema of the infrapatellar fat pad is observed in acute rheumatoid arthritis but is not commonly observed in chronic long-standing rheumatoid arthritis which is more frequently found in association with complicating bacterial arthritis (12). We have also observed that the joint effusions caused by complicating pyarthrosis are in general considerably larger than those associated with rheumatoid arthritis alone. In addition, marked asymmetry in soft-tissue changes when compared with the opposite side coupled with the information of progressive monarticular swelling and pain should allow the presumptive diagnosis of complicating pyarthrosis to be made. The soft-tissue changes are most helpful in joints where the fat interface is more prominent such as the knee and ankle because of the larger amount of adjacent intracapsular and extracapsular fat, respectively. In contrast, these soft-tissue changes are more subtle and less dependable in joints such as the wrist and hip where there

is a paucity of adjacent extracapsular fat, making the radiologist rely more upon bony articular changes in these joints. Consequently, superimposed sepsis is more likely to be detected earlier radiographically in the knee and ankle because of the different soft-tissue anatomy. Although the presence of the previously described soft-tissue and bony changes must be regarded as highly suggestive of complicating pyarthrosis, needle aspiration must be performed for confirmation, identification of the infecting organism, and choice of proper antibiotic. ACKNOWLEDGMENT: The authors wish to express their appreciation to Mrs. LeVern Jarrad for her capable assistance in the preparation of the manuscript. Department of Radiology University of Utah Medical Center 50 North Medical Drive Salt Lake City, Utah 84132

REFERENCES 1. Ball J: Rheumatic Diseases. Baltimore, Williams and Wilkins, 1968, p 123 2. Baum J: Infection in rheumatoid arthritis. Arthritis Rheum 14:135-137, Jan-Feb 1971 3. Bodel PT, Hollingsworth JW: Comparative morphology, respiration. and phagocytic function of leukocytes from blood and joint fluid in rheumatoid arthritis. J Clin Invest 45:580-589, Apr 1966 4. Butt WP: Radiology of the infected joint. Clin Orthop 96: 136-149, Oct 1973 5. De Andrade JR, Tribe CR: Staphylococcal septicaemia with pyoarthrosis in rheumatoid arthritis. Report of three fatal cases. Brit Med J 1:1516-1518, 2 Jun 1962 6. Gristina AG, Rovere GO, Shoji H: Spontaneous septic arthritis

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SEPTIC ARTHRITIS

23

Diagnostic Radiology

Fig. 7. A, Band C. Progressive asymmetrical destruction of articular surfaces and joint space narrowing (black arrows) over a 13-week interval should indicate superimposed pyarthrosis. Edema of the retrotibial fat pad is also present and progressive (white arrows). D. Opposite uninvolved ankle demonstrating marked asymmetry and preserved retrotibial fat pad (arrows). complicating rheumatoid arthritis. J Bone Joint Surg 56A: i 180-1184, Sep 1974 7. Karten I: Septic arthritis complicating rheumatoid arthritis. Ann Intern Med 70: 1147 -1158, Jun 1969 8. Kellgren JH, Ball J, Fairbrother RW, et al: Suppurative arthritis complicating rheumatoid arthritis. Br Med J 1:1193-1200, 24 May 1958 9. Myers AR, Miller LM, Pinals RS: Pyarthrosis complicating rheumatoid arthritis. Lancet 2:714-716,4 Oct 1969

10. Pruzanski W, Leers WD, Wardlaw AC: Bacteriolytic and bactericidal activity of sera and synovial fluids in rheumatoid arthritis (abst). Arthritis Rheum 14:409, May-Jun 1971 11. Russell AS, Ansell BM: Septic arthritis. Ann Rheum Dis 31: 40-44, 1972 12. Weston JW: Personal communication 13. Wilkens RF, Healey LA, Decker JL: Acute infectious arthritis in the aged and chronically ill. Arch Intern Med 106:354-364, Sep 1960

Septic arthritis: a complication of rheumatoid arthritis.

• Septic Arthritis: A Complication of Rheumatoid Arthritis 1 • Diagnostic Radiology Martin I. Gelman, M.D., and John R. Ward, M.D. Eighteen cases...
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