Aseptic inflammation of prosthetic knee in a patient affected by rheumatoid arthritis

Description

A woman aged 40 years affected by an aggressive and active form of rheumatoid arthritis (RA) underwent total knee arthroplasty (TKA) of the left knee for persistent synovitis after several therapeutic lines, the last one included methotrexate and a TNF-inhibitor.

Two months after the surgical procedure, the patient reported mild fever and persistent swelling of the left knee. On examination, there were signs of inflammation but no effusion to drain. Ultrasonography only showed oedema of the tissues surrounding the knee, and therefore, suspecting a prosthetic infection, antibiotic therapy was immediately started.

A subsequent scintigraphy with 99mTC-HmPAO (hexamethylpropylene-amine-oxime)-labelled leucocytes demonstrated the presence of early and persistent accumulation of labelled leucocytes in the femoral and tibial periprosthetic soft tissues, supporting the hypothesis of prosthetic infection (figure 1A).

Figure 1

(A) Images of the scintigraphy with 99mTC-HmPAO (hexamethylpropylene-amine-oxime)-labelled leucocytes, showing early and persistent (after 4 hours) accumulation (black...

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