Unexpected positive cultures after revision shoulder arthroplasty -does it affect outcome?
These authors point out that specimens obtained at the time of "apparently aseptic" revision arthroplasties are frequently culture positive for Cutibacterium.
They studied 124 patients who had revision shoulder arthroplasties that were revised for reasons other than suspicion of infection.
Their treatment anticipated that a substantial number of the cases would be culture positive. A standardized single-stage exchange was performed after vigorous debridement and antibiotic irrigation with a Vancomycin and Gentamycin solution. An anatomic total shoulder replacement was implanted in patients with an intact and functional rotator cuff, and a reverse shoulder arthroplasty was implanted in patients with an absent or non-functional rotator cuff.
Preoperative antibiotics were withheld until five biopsy specimens were obtained for culture on blood agar, on anaerobic agar plates, and in semisolid agar+pepsis blood+thioglycollate.
After culture specimens were obtained, an IV dose of either 1.5 g cefuroxim or 1 g dicloxacillin was administered.
Postoperative IV antibiotics were continued for the first 24 hours, and patients were prescribed either oral or IV antibiotic treatment covering Cutibacterium until the cultures were finalized at 14 days.
Shoulders were defined as culture-positive if growth with identical bacteria was detected in at least three of the five biopsy specimens. If growth in less than three biopsy specimens was present, then the shoulder was designated as culture-negative. If cultures exhibited growth at readings up to the fourth postoperative day, then 2 weeks of IV treatment were initiated, followed by 4 weeks of oral treatment. If cultures were positive at the reading on the 14th postoperative day, then an additional 4 weeks of oral treatment were recommended. Both IV and oral antibiotic treatments were based on the antibiogram of the cultured microorganism and recommendations from the local microbiology department. Antibiotic treatment was discontinued if cultures were negative on the 14th postoperative day.
27 (22% ) had cultures with the same bacteria in at least three biopsy specimens; these shoulders were classified as culture-positive. Cutibacterium accounted for 67% (18/27) of these.
At baseline, the Oxford Shoulder Score was 22 in both the culture-negative and culture-positive groups. At follow-up, the OSS was 37 in the culture-negative group and 35 in the UPC group. The forward elevation increased significantly by 44° and 41° respectively in the two groups.
Thus with their surgical and antibiotic management protocol that anticipated the strong possibility of positive cultures, they did not find a difference in outcome after revision arthroplasty regardless of whether or not the intraoperative cultures were positive.
Comment: This study clearly demonstrates that substantially positive cultures of deep tissue specimens obtained at surgical revision of "apparently aseptic" failed shoulder arthroplasties can no longer be referred to as "unexpected" - rather they can be expected in more than one out of five cases. It is time to retire the term "unexpected positive cultures".
This study also demonstrates good results can be obtained by treating all revisions as if they are expected to be positive until culture results prove otherwise.
The result of this study are essentially the same as those of a previous paper:
