These authors reviewed all 2,288 total hip arthroplasty (THA) revisions performed at their institution from 2006 to 2019. Of these 1196 did not have preoperative evidence of infection ("presumed aseptic revision"). Three to five samples were obtained for culture at the time of revision. Positive cultures were documented for 9.2% (110) of the 1,196 presumed aseptic THA revisions. 68% of the cases had one positive culture while 32 had two or more positive cultures. 38% of the positive cultures were for Cutibacterium, 13% for Methicillin resistant Staph Epidermidis, 11% for other coagulase negative Staph, 9% for Methacilling sensitive Staph, 5% for micrococcus.
41 (38%) were treated with antibiotics (10 oral alone, 9 IV alone, 22 oral and IV).
The 2- and 5-year infection-free implant survival rates for the 1196 revisions were 93.1% and 86.8%.
The 2- and 5-year infection-free survival with failure due to infection with the same microorganism as identified in the initial revision as the end point were 95.8% and 94.3%, respectively.
Subsequent infection-related failures caused by the same microorganism as identified in the initial revision were more likely to occur after revisions with ≥2 positive culture than after those with only 1 positive culture.
They defined adverse metal reactions as any adverse local tissue reaction (ALTR), including “pseudotumors,” due to metal ions causing failure of the total joint replacement including metal-on-metal bearings, corrosion of the head-neck junction in metal-on-polyethylene bearings (“trunnionosis”), or recalled modular stems at the modular neck-stem junction. Of the variables included in multivariate Cox regression analysis, only revision for adverse metal reaction was significantly associated with an increased risk of subsequent infection-related failure; revision for adverse metal reaction was a risk factor for subsequent infection-related failure (hazard ratio [HR] = 14.4).
Patients with a single positive culture at the initial revision who were not treated with antibiotics had no subsequent periprosthetic joint infections (PJIs) caused by the same microorganism as identified in the initial revision.
Comment: Here are a few of the lessons we can learn from this study
(1) In these "apparently aseptic" cases of PJI with positive intraoperative cultures, Cutibacterium was the most common organism isolated from deep cultures.
It is of note that most cases of shoulder PJI do not have preoperative evidence of infection and could be referred to as "apparently aseptic", i.e. "stealth" infections. Cutibacterium is the most common organism isolated from shoulder PJI.
(2) The authors found that their increased detection of Cutibacterium compared with most
studies may be due to the extended 10-day anaerobic incubation time for their cohort.
We hold all cultures obtained at revision shoulder arthroplasty for 14 days.
(3) An increased load of bacteria (as reflected by the number of positive cultures) found at revision arthroplasty was associated with failure of the revision to resolve the infection.
We go one step further in determining the bacterial load by quantitating not only the number of positive cultures but also the degree of positivity of each one. See 10 points about Cutibacterium, periprosthetic infection, and revision for failed shoulder arthroplasty.
(4) Metal sensitivity may increase the likelihood of periprosthetic infection as well as the difficulty in resolving a PJI.
The relationship of metal sensitivity to PJI surely merits further study. See Acute delayed infection: increased risk in failed metal on metal total hip arthroplasty and High rate of infection after aseptic revision of failed metal-on-metal total hip arthroplasty
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