2009 Abstract : 13

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Authors: Lanting B, Ralph E, Naudie D, London, Ontario

Title: Pseudallescheria boydii Total Knee Arthroplasty Infection: A Case Report, Treatment and Review of Literature

Purpose: A unique case of an otherwise healthy 64 year old male with a total knee arthroplasty infected with Pseudallescheria boydii is outlined in the context of the current literature with case presentation, treatment course, and definitive management.

Methods: A 64 year old male underwent elective right total knee arthroplasty at another institution three years prior to presentation. He sustained an acute tibiofemoral dislocation of his prosthesis initially, and was revised to a thicker polyethylene insert three months after his initial surgery. Five months later, because of residual instability, he fell on a farm and sustained an open peri-prosthetic supracondylar fracture. He was treated with lateral plate fixation, and subsequently required five irrigation and debridement surgeries to control ongoing drainage and suspected infection of his fracture site. He was treated with long courses of intravenous antibiotics. His intra-operative cultures were consistently negative but he continued to show signs of an infected non-union.
He sought a second opinion in a tertiary care centre and an aspiration of his knee joint ultimately grew Scedosporium apiospermum-the asexual state of P. boydii. Prior to knowing this culture report, he was started on vancomycin, but no significant change in symptoms occurred. He was referred presented to our institution for a third opinion in October of 2008 with a painful, swollen knee, a limited range of motion (10 - 45o), and a large laterally based fluid collection. His radiographs demonstrated non-union of his supracondylar fracture above his total knee arthroplasty, with retained antibiotic beads (Figure 1). His ESR was seven and CRP was two. A repeat knee aspiration was performed and was positive for coagulase negative staphylococci and aerobic spore-forming bacilli. He was scheduled for a staged knee revision with an antibiotic-impregnated spacer to treat the infected non-union of his distal femur as well as the infected total knee arthroplasty.

Results: Exposure was difficult, requiring a quadriceps snip, and the infected beads, plate and knee arthroplasty were removed. During the aggressive irrigation and debridement, no white grains characteristic of P. boydii were found. An articulating polymethylmethacrylate (PMMA) spacer was impregnated with 10.0 grams vancomycin and 9.6 grams of tobramycin. An unlocked intramedullary rod was inserted into his femur to stabilize the non-united fracture (Fig 2). Intravenous vancomycin was started to treat the coagulase negative staphylococcus; the presumed infecting organism. Intra-operative cultures were reported positive only for an unspeciated fungus which a reference laboratory identified as P. boydii. The vancomycin was discontinued and voriconazole was initiated. A second surgery was required at two weeks to remove a retained sequestrum of dead bone. After three months, the oral voriconazole was discontinued, and after six weeks, there were no signs of re-infection. His inflammatory markers (ESR, CRP) were normal. He then underwent a revision total knee arthroplasty with long intramedullary stems. Intra-operative cultures were negative for fungi and bacteria. A six week post-operatve course of voriconazole was initiated.

Discuassion and Conclusion: P. boydii is environmentally ubiquitous. It is more commonly infectious in immunocompromised than immunocompetent patients. It is implicated after near drowning or in mycetoma pada. Infection by P. boydii of a joint arthroplasty or other prosthesis has not been reported. The importance of a complete infectious work-up-including fungal cultures-in a clinically infected prosthesis with negative bacterial cultures is seen. Open fractures sustained on a farm and multiple unsuccessful attempts at irrigation and debridement should heighten suspicion of a fungal contamination. Speciation is required to guide treatment. P. boydii is not responsive to the usual anti-fungal agents including amphotericin b, caspofungin and fluconazole. Recently FDA approved agents such as voriconazole and posaconazole are required. Information regarding the presence of a fungal biofilm, penetration of it by anti-fungals and elution properties from cement is also unknown. Treatment in this case involved removal of the infected prosthesis, placement of an antibiotic spacer and stabilization of the non-union in conjunction with oral anti-fungal agents. After the fungus was eradicated, a revision total knee arthroplasty was performed successfully.