Dodson and colleagues reviewed Propionibacterium acnes infections after shoulder arthroplasty to describe how they presented, how they were diagnosed and how they were treated.
Retrospective review of 11 patients (mean age 60.1) whose shoulder arthroplasty became infected with P acnes, treated at the Hospital for Special Surgery 2002 to 2006 and followed a mean 4.0 years.
Key Findings
No patient had fever or a leukocyte count above 10,000. ESR and CRP were more informative, as in earlier reports: by the authors' count, 5 of 11 had ESR of 30 mm/h or more and 8 had CRP of 1.0 mg/dL or more.
Cultures took a mean of 9 days to turn positive (8 to 10). Many laboratories discard samples after 3 to 5 days.
Every isolate was sensitive to penicillin and clindamycin and resistant to metronidazole, unlike most anaerobes.
Six patients revised for mechanical problems had no preoperative suspicion of infection. Their cultures turned positive after discharge, and all chose antibiotics instead of further surgery.
Among the 5 with suspected infection, staged exchange resolved it in 3. One needed another debridement, and one needed 3 debridements and then explantation.
Preoperative aspiration grew the organism in 1 of 2 patients aspirated. The authors find aspiration most useful when imaging shows a distinct fluid collection.
Board pearl
P acnes cultures must be held at least 8 days before being called negative. The authors now hold all cultures from possible surgical‑site infections for at least 10 days.
Authors' conclusion
In conclusion, although this is a small series, it demonstrates that P acnes can be a true pathogen in the setting of shoulder arthroplasty and underscores that variables such as ESR, WBC, CRP, local wound condition, preoperative joint aspiration, and even intraoperative cultures if discarded prematurely can cloud the diagnosis of a clinically significant joint infection.
Dodson and colleagues reviewed Propionibacterium acnes infections after shoulder arthroplasty to describe how they presented, how they were diagnosed and how they were treated.
Retrospective review of 11 patients (mean age 60.1) whose shoulder arthroplasty became infected with P acnes, treated at the Hospital for Special Surgery 2002 to 2006 and followed a mean 4.0 years.
Key Findings
No patient had fever or a leukocyte count above 10,000. ESR and CRP were more informative, as in earlier reports: by the authors' count, 5 of 11 had ESR of 30 mm/h or more and 8 had CRP of 1.0 mg/dL or more.
Cultures took a mean of 9 days to turn positive (8 to 10). Many laboratories discard samples after 3 to 5 days.
Every isolate was sensitive to penicillin and clindamycin and resistant to metronidazole, unlike most anaerobes.
Six patients revised for mechanical problems had no preoperative suspicion of infection. Their cultures turned positive after discharge, and all chose antibiotics instead of further surgery.
Among the 5 with suspected infection, staged exchange resolved it in 3. One needed another debridement, and one needed 3 debridements and then explantation.
Preoperative aspiration grew the organism in 1 of 2 patients aspirated. The authors find aspiration most useful when imaging shows a distinct fluid collection.
Board pearl
P acnes cultures must be held at least 8 days before being called negative. The authors now hold all cultures from possible surgical‑site infections for at least 10 days.
Authors' conclusion
In conclusion, although this is a small series, it demonstrates that P acnes can be a true pathogen in the setting of shoulder arthroplasty and underscores that variables such as ESR, WBC, CRP, local wound condition, preoperative joint aspiration, and even intraoperative cultures if discarded prematurely can cloud the diagnosis of a clinically significant joint infection.