Postoperative infections of the shoulder - demographics and prevention

• Updated on: 2023-06-16
• Read original article here

Shoulder Arthritis / Rotator Cuff Tears / Shoulder Pain
Sunday, April 2, 2023
Postoperative infections of the shoulder - demographics and prevention
Shoulder infections are important causes of failed shoulder surgery. Here is a case of a total shoulder periprosthetic infection by Cutibacterium
A number of recent publications are of interest.
I. The authors of The POSI study: gender differences in 94 cases of postoperative shoulder surgery infection: results of a 7-year retrospective multicenter study reported the characteristics of patients experiencing postoperative shoulder infections. A confirmed shoulder infection was defined as 2 positive cultures or more of the same microorganism, or clear clinical infection with 1 positive culture.
The mean patient age at index surgery was 59 years (range: 22-91) with a majority being men (74%). Arthroplasty was the most common index surgery, followed by fracture fixation, arthroscopic surgery, and other open procedures.
The median time between the index surgery and the first positive sample was 5 months (mean 23 months, minimum 6 days to maximum 27 years). The median time between index surgery and diagnosis for cases with Cutibacterium infections was 8.6 months in contrast to 3.9 months for other organisms.
Cutibacterium species were identified in 64 patients (68%), 59 of which were Cutibacterium acnes (63%). In 86% of cases, Cutibacterium was identified at the first revision. The other 2 most common germs were Staphylococcus epidermidis and Staphylococcus aureus, (29% and 17%, respectively). Polymicrobial infection was present in 30% of patients.
Cutibacterium was twice as frequent in men.
S. epidermidis was twice as frequent in women.
S. epidermidis was 3 times more prevalent in chronic than in acute cases.
Comment: Of note: (1) the long intervals between the index procedure and diagnosis, especially for Cutibacterium infections, (2) the sex difference in frequency of Cutibacterium and S. epidermidis, and (3) 5 of the 64 Cutibacterium infections were by species other than C. acnes.
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II. What is the best IV prophylaxis against shoulder infections? As detailed in this link , cephalosporin antibiotics are most effective in preventing shoulder infections from the two most common causative organisms: Cutibacterium and coagulase negative Staphylococcus. This  link  also addresses the situation in which the patient reports a penicillin allergy. 
Patients with penicillin "intolerance" history
and patients with low risk penicillin allergy history
can be given cephalosporins with low risk of reactions. Whereas patients with high risk history of penicillin allergy
shoulder receive an alternative antibiotic. Clindamycin is not a good second choice because of the relatively high prevalence of Cutibacterium resistance to this organism. 
The authors of  When intravenous vancomycin prophylaxis is needed in shoulder arthroplasty, incomplete administration is associated with increased infectious complications  point out that vancomycin is often used as antimicrobial prophylaxis for shoulder arthroplasty (SA) either when cephalosporins are contraindicated or colonization with resistant bacteria is anticipated. Vancomycin is recognized as being inferior to cephalosporins in preventing Cutibacerium infections, possibly due to a higher minimum inhibitory concentration required to eradicate infection; thus, weight-based dosing is important. Vancomycin is different than most other antibiotics used in prophylaxis: it necessitates longer infusion times to mitigate potential side effects, such as Red Man Syndrome or Vancomycin flushing syndrome . When infusion is started too close to the time of the incision, administration may not be complete during surgery. 
These authors evaluated whether incomplete administration of intravenous vancomycin prior to SA affects the rate of infectious complications in primary shoulder arthroplasties (hemiarthroplasty, anatomic total SA, or reverse SA) with minimum two-year followup.
A total of 461 primary SAs were included. Vancomycin infusion was considered incomplete if the administration was not finished by 30 minutes preoperatively. (163 cases), and complete if administration was finished more than 30 minutes preoperative. (298 cases). 
The incomplete group demonstrated significantly higher rates of any infectious complication (8% vs. 2.3%); periprosthetic infection (5.5% vs. 1%), and reoperation inclusive of revision due to infectious complications (4.9% vs. 1%). 
Survivorship free of PJI was worse in SA with incomplete compared to those with complete vancomycin administration. Survival rates for incomplete and complete administration were 
97.6% and 99.3% at 1 mo, 
95.7% and 99.0% at 2 yr, 
95.1% and 99.0% at 5 yr, and 
93.9% and 99.0% at 20 yr, respectively. 
Multivariable analyses confirmed that incomplete vancomycin administration was an independent risk factor for PJI compared with complete administration (hazard ratio, 4.22), even when other independent predictors of PJI (age, male sex, prior surgery, methicillin-resistant Staphylococcus aureus colonization, and follow-up) were considered.
Comment: It is of interest that in this series from a major academic medical center, over one-third of the cases had incomplete administration of vancomycin and that those cases with incomplete administration had over 4 times the rate of infectious complications than those with complete administration. This observation suggests that it is important to obtain high blood concentrations prior to the surgical incision in order to reduce the inoculation of the wound by organisms inhabiting the dermis, such as Cutibacterium, which are not eliminated by the standard surgical skin surface preparations. The desired blood level cannot be achieved if vancomycin administration is started in the operating room because of the need for slow infusion to minimize side effects - the infusion needs to be started in the pre-operative holding area.
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III. TopIcal vancomycin
As described above, achieving high tissue levels of vancomycin with IV administration can be difficult because of the limitations on the rate of administration, because of concern about vancomycin toxicity if the weight-based dosage is exceeded, and because of the difficulties in adhering to the ideal administration timing. These concerns might be effectively addressed by the topical, rather than systemic administration of vancomycin. The authors of  Vancomycin powder embedded in collagen sponge decreases the rate of prosthetic shoulder infection  sought to evaluate whether Vancomycin powder embedded in a collagen sponge could decrease the rate of prosthetic shoulder infection.
They conducted a retrospective analysis of 827 patients undergoing Total Shoulder Arthroplasty (TSA) with 405 patients having no topical vancomycin and a group of 422 having the intraoperative application of intrawound vancomycin powder. Of note these two groups were not assigned randomly and the patients in each group were not systematically matched. Instead, the authors changed their protocol over the time of the study to include topical vancomycin. 
After 1 year of observation, no infections were observed in the group treated with intrawound vancomycin; 13 cases of infection (3.2%) were observed in the group without vancomycin application. No wound complications requiring revision were observed as a result of intrawound vancomycin. 
IV. Nipping it in the bud
Cutibacterium has the ability to form biofilms, especially on the titanium alloy implants from which many shoulder arthroplasty components are mode. These biofilms protect the sessile organisms from host defenses and antibiotics. Thus the best chance to reduce the size of the Cutibacterium inoculum at the time of primary shoulder arthroplasty is to use agents that act against the organism while it is in its planktonic stage, i.e. before it becomes sessile in a biofilm on the implants. Vancomycin's minimum inhibitory concentration against planktonic Cutibacterium is 0.38 μg/mL while the vancomycin concentration required to eradicate an established biofilm is estimated to be ≥128 μg/mL.  A recent study showed that the concentrations of vancomycin that could be achieved in vivo were effective against planktonic Cutibacterium:  In vitro susceptibility of Propionibacterium acnes [Cutibacterium] to simulated intrawound vancomycin concentrations.  The authors concluded that when administered in a fashion meant to simulate time-dependent in vivo intrawound concentrations, vancomycin exhibited bactericidal activity against P. acnes.
The authors of another study,  Vancomycin is Effective in Preventing C. acnes Growth in a Shoulder Arthroplasty Mimetic  found that vancomycin administration effectively prevented Cutibaterium growth in a bioartificial shoulder joint mimetic implant. 
The size of reduction in the rate of periprosthetic joint infections necessary to justify the cost of topical vancomycin was assessed in:  The cost effectiveness of vancomycin for preventing infections after shoulder arthroplasty: a break-even analysis These authors concluded that prophylactic administration of local vancomycin powder during shoulder arthroplasty could be highly cost-effective. They estimated that the overall cost to treat an infection is $46,745. Vancomycin costs vary from $2.50 to $44 per gram of vancomycin. At $2.50 per gram, vancomycin only needs to obtain an efficacy of 0.005% in reducing the rate of PJI to be cost-effective, whereas at $44 per gram, the efficacy needs to be 0.09% to be cost- effective.
What we know: 
1. Cutibacterium is the commonest organism to cause shoulder periprosthetic infections; the risk of these infections is increased in young male patients.
2. Cutibacterium live in the dermal pilosebaceous units of the skin overlying the shoulder where they cannot be eradicated by surgical skin surface preparations or by preoperative intravenous antibiotics
3. These dermal pilosebaceous units are incised at shoulder arthroplasty surgery, allowing planctonic Cutibaterium to contaminate the surgical field.
4. If not controlled by host defenses and prophylactic methods, these contaminating organisms can cause shoulder periprosthetic infections that are disabling for the patient and difficult to resolve once a biofilm is formed.
5. The use of topical in-wound Vancomycin appears to be safe and relatively inexpensive.
6. The clinical value of topical in-wound Vancomycin in reducing or eliminating Cutibacterium from the surgical field has yet to be rigorously demonstrated, but deserves careful study.
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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this  link ).
How to x-ray the shoulder (see this  link ).
The ream and run procedure (see this  link ).
The total shoulder arthroplasty (see this  link ).
The cuff tear arthropathy arthroplasty (see this  link ).
The reverse total shoulder arthroplasty (see this  link ).
The smooth and move procedure for irreparable rotator cuff tears (see this  link ).
Shoulder rehabilitation exercises (see this  link ).
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