Pyoderma gangrenosum mimicking early acute infection following total knee arthroplasty.

Case Report A 56-year-old male presented 6 days post-TKA with fi ndings mimicking wound infection. He underwent wound debridement limited to the cutaneous and subcutaneous layers, followed by a Vacuum Assisted Closure® (VAC) dressing (KCI, Texas, USA), as there was no apparent involvement of the knee joint. He was started on intravenous amoxicillin and clavulanate once intraoperative cultures were taken. Debridement was performed again 9 days post-TKA. Extensive subcutaneous necrosis and skin pustules were noted. Debridement, arthrotomy, exchange of the polyethylene insert and VAC dressing were done. He underwent further debridements at 11 and 14 days post-TKA. There was never any pus or slough within the joint cavity and debridements were performed to healthy margins. All 8 tissue samples sent were negative for microbial growth. Histological studies revealed non-specifi c acute infl ammatory and reactive changes. Notably, surgery seemed to aggravate the cutaneous and subcutaneous involvement. Figure 1A shows an intraoperative photo at the third round of debridement. Fifteen days post-TKA, a dermatologist was consulted and a diagnosis of PG was made. Atypical features of this case include the lack of associated conditions, seronegativity for rheumatoid factor and an absence of satellite lesions. Oral prednisone (at 0.5 mg/kg) was started. Repeat debridement 2 days later showed improvement at the cutaneous and subcutaneous layers (Fig. 1B). C-reactive protein (CRP) and white blood cell (WBC) counts trended lower. The insert was changed, intra-articular washout performed and wound coverage achieved with a medial gastrocnemius fl ap and split skin grafting (Fig. 1C). Oral prednisone was tailed off over a period of 30 days. The fl ap and skin graft healed well, without any recurrence of PG.