Most periposthetic infections (PJI) of the shoulder are culture positive for Cutibacterium rather than for other bacteria. However, when a failed shoulder arthroplasty is being surgically revised, it is difficult to know whether intraoperative cultures will be positive, because this organism does not cause the inflammatory signs typical of infection. As a result, current laboratory approaches do not provide a practical method for the accurate prediction of a Cutibacterium periprosthetic joint infection (PJI) in failed arthroplasties. Therefore, surgeons revising failed arthroplasties must decide whether to exchange the implants and to institute antibiotic treatment without knowing the results of cultures of deep specimens obtained at the revision procedure. These authors tested the hypothesis that the results of preoperative culture specimens of the skin surface obtained in the clinic can predict the presence of culture-positive Cutibacterium PJIs.
Culture results are expressed as the specimen values: 0 for no growth, 0.1 for growth in broth only or for 1 colony only on a plate, 1 for 1+growth, 2 for 2+ growth, 3 for 3+growth, and 4 for 4+ growth on a plate, where the values from 1 to 4 indicate the number of quadrants on the streaked plate showing growth.
The percentage of the total skin bacterial load contributed by Cutibacterium (Cutibacterium percentage = load of Cutigacterium/total load of all bacteria in the specimen) was determined.
A robust criterion for culture-positive Cutibacterium PJI was applied: ≥2 surgical specimens each with a Cutibacterium value of ≥1.
The predictive values for a culture-positive Cutibacterium PJI were determined for a clinic skin culture Cutibacterium value of >1 and a clinic skin percentage of Cutibacterium of ≥75%.
Of the eighteen revision arthroplasty cases included in the study, 7 (6 male patients) met the criterion for a culture-positive Cutibacterium PJI.
In this figure, the specimen values are shown for Cutibacterium (Cuti), coagulase-negative Staphylococcus (CoNS), and other bacteria, comparing shoulders without (no PJI) and those with (PJI) a Cutibacterium PJI. Specimen values are shown for the preoperative cultures in the clinic, for the preoperative cultures in the operating room (OR), and for the dermis freshly incised at the revision surgical procedure.
A preoperative clinic skin Cutibacterium value of >1 predicted the presence of a culture positive Cutibacterium PJI with an accuracy of 89%.
A clinic skin Cutibacterium percentage of ≥75% predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 94%.
For male patients, a preoperative clinic skin Cutibacterium value of >1 predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 91%, and a clinic skin Cutibacterium percentage of ≥75% predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 100%.
The authors presented a case showing the utility of preoperative clinic culture specimens. A 60-year-old man presented with increasing shoulder pain and stiffness of insidious onset at 2 years after a short-stemmed total shoulder arthroplasty performed at an outside hospital. He was a nonsmoker in good health with a BMI of 28 and ASA class of 2. He had no systemic signs or laboratory evidence of infection. His pre-revision radiograph suggested humeral component loosening. A preoperative clinic swab of his unprepared skin over the shoulder incision area grew 3+ Cutibacterium, 1+ coagulase-negative Staphylococcus, and no other organisms, for a Cutibacterium percentage of 75%. At the time of the surgical procedure, there was no synovitis, no free joint fluid, and a loose humeral component. Frozen sections of the periprosthetic tissue showed no neutrophils and no organisms.
In spite off these intraoperative findings, the preoperative skin cultures suggested a strong possibility of Cuitbacterium PJI. Thus he had a single-stage revision of the total shoulder arthroplasty to a ream-and-run arthroplasty with impaction allografting of a standard smooth stem inserted after thorough debridement and irrigation. Immediately after the surgical procedure, he was administered intravenous ceftriaxone through a peripherally inserted central catheter. When his intraoperative cultures were finalized at 3 weeks after the surgical procedure, they showed 3+ Cutibacterium growth from the explanted stem, 2+ growth from the humeral-head component, 1+ growth from the glenoid component, and 0.1 growth from each of the humeral periosteum, the collar membrane, and the humeralmembrane, for a Shoulder Score for Cutibacterium of 6.3 points and a mean Shoulder Score for Cutibacterium of 1.1 points. No other types
of bacteria were recovered from his surgical specimens.
Conclusions: A simple culture specimen of the unprepared skin surface obtained in a clinic prior to revision shoulder arthroplasty may provide valuable assistance to surgeons planning a revision arthroplasty.
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