Predicting infection risk in shoulder arthroplasty

Cutaneous microbiology of patients having primary shoulder arthroplasty

These authors point out that shoulder periprosthetic infections are predominantly caused by bacteria residing in the skin of healthy individuals.

They tested the hypothesis that easy-to-obtain preoperative characteristics were significantly associated with the cutaneous microbiology and the loads of specific bacteria in shoulders having joint replacement.

They identified the microbiology of the unprepared epidermal skin surface and of the dermal edge freshly incised at surgery in 332 patients having primary shoulder arthroplasty.

The load of bacteria in each sample was characterized as a value based on the laboratory report: 0 for “no growth”; 0.1 for “one colony only” or for “broth only”; and 1, 2, 3, and 4 for 1+, 2+, 3+, and 4+ growth, respectively.

Cultures of the unprepared epidermal skin surface showed positive results for a wide variety of organisms, including Cutibacterium in 72%, coagulase-negative Staphylococcus in 61%, and a spectrum of other organisms in 32%.

By contrast, cultures of the freshly incised dermal edge showed a great preponderance of Cutibacterium (34%) in comparison to low levels of coagulase-negative Staphylococcus (8%) and other organisms (2%).

An increased dermal load of Cutibacterium was significantly associated with male sex (p<.001), younger patient age (p<.001), American Society of Anesthesiologists class 1 (p 0.046), use of testosterone supplements (p 0.014), prior shoulder surgery (p 0.046, and higher Cutibacterium loads on the unprepared skin surface (p<.001)

They concluded that although the microbiology of the unprepared skin surface is diverse, the same is not true for the freshly incised dermis, where Cutibacterium is the predominant organism.

Readily available preoperative patient characteristics were significantly associated with the load of Cutibacterium in the incised dermis.

Preoperative cultures of the unprepared skin surface appear to be a new method for predicting the type and load of bacteria found in the freshly incised dermis at the time of surgery.

Comment:  Knowledge of the preoperative characteristics of patients likely to have high dermal loads of Cutibacterium may help identify those for whom extraordinary means of prophylaxis (such as Betadine lavage, in-wound topical antibiotics, extended postoperative antibiotics) may be indicated to reduce the risk of periprosthetic infection.

The relationship of male sex, young age, good health, and testosterone supplements to the dermal load of Cutibacterium is consistent with previous observations that higher levels of male sex hormones are associated with increased sebum production in dermal pilosebaceous units and a commensurate increase in the number of Cutibacterium in these dermal structures.

It is of interest that the risk factors for higher loads of Cutibacterium in the dermal incisions for elective shoulder arthroplasty are quite different from the risk factors characteristically associated with periprosthetic infections of the hip and knee, which include older age, female sex, diabetes, high ASA score, obesity, and Medicaid insurance coverage.

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We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art"  regarding this radically conservative approach to shoulder arthritis at this link and this link

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages   arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Shoulder joint replacement - does hydrogen peroxide reduce Cutibacterium risk?

Hydrogen peroxide skin preparation reduces Cutibacterium acnes in shoulder arthroplasty: a prospective, blinded, controlled trial

These authors sought to determine whether preoperative skin preparation with hydrogen peroxide reduces intraoperative culture positivity for Cutibacterium acnes in shoulder arthroplasty.

They included a consecutive series of patients scheduled to undergo primary anatomic or reverse total shoulder arthroplasty. First, for both cohorts, they wiped the skin with 70% ethyl alcohol and then prepared the skin with ChloraPrep. In the control group, they did not perform any further skin preparation. In the peroxide group, they wiped the skin with 3% hydrogen peroxide between the alcohol and ChloraPrep steps. In all cases, they applied an occlusive, adherent, iodine-impregnated drape after the prep.

After incision, they took aerobic and anaerobic cultures using swabs. First, they lifted the adherent dressing from the skin, and took 1 culture from the surface of the skin. Second, they took 1 culture from the incision edge along the dermis. Third, they took 1 culture from the humeral articular surface. Fourth, they waved 1 culture in the air as a negative control. 

There were fewer patients within the peroxide group with triple-positive cultures (skin, dermis, and joint) (0% vs. 19%, P . .024) and positive cultures from the joint (10% vs. 35%, P . .031).

 The vast majority of positive cultures were for C. acnes.

The differences were only significant in males. 

Comment: This was a very carefully done study, but it raises some important questions:
(1) How do we interpret the observation that in primary male arthroplasties 44% of the humeral head cultures were positive? Were these bacteria in place before the incision, or were they contaminated by blood from the incised dermis (which was culture positive in 50%)?
(2) How do we incorporate the finding that one in seven of the air cultures were positive? Is this evidence of unsterile air in the OR or does it raise the possibility of specimen contamination during handling?
(3) In that the hydrogen peroxide was applied to the skin surface, why was there no difference in skin culture positivity between the treated and untreated skin (31% vs 31%)?
(4) Of the three culture sites (skin, dermis and joint), why was the joint - the furthest site from the application of hydrogen peroxide -  the only site to show a significant reduction in the rate of culture positivity?
(5) Since the "wipe" of hydrogen peroxide application was followed immediately by the application of ChloraPrep, was there enough time for the hydrogen peroxide to penetrate the skin?

This study can be compared to that posted below
Preoperative Skin-Surface Cultures Can Help to Predict the Presence of Propionibacterium in Shoulder Arthroplasty Wounds 

Propionibacterium species are commonly cultured from specimens harvested at the time of revision shoulder arthroplasty. These bacteria reside in normal sebaceous glands, out of reach of surgical skin preparation. The arthroplasty incision transects these structures, which allows Propionibacterium to inoculate the wound and to potentially lead to the formation of a biofilm on the inserted implant. To help identify patients who are at increased risk for wound inoculation, these authors investigated whether preoperative cultures of the specimens from the unprepared skin surface were predictive of the results of intraoperative cultures of dermal wound-edge specimens obtained immediately after incision of the surgically prepared skin.

Sixty-six patients (mean age, 66.1 ± 9.4 years [range, 37 to 82 years]; 73% male) undergoing primary shoulder arthroplasty had preoperative cultures of the unprepared skin surface and intraoperative cultures of the freshly incised dermis using special culture swabs.

For the first 50 patients, a control swab was opened to air during the same time that the dermal specimen was obtained.

The results for female and male patients were characterized as the Specimen Propionibacterium Value (SpPV). The authors then determined the degree to which the results of cultures of the skin surface specimens were predictive of the results of culture of the dermal specimens.

An example of this semiquantitative reporting is shown below for the 21-day cultures of specimens from a 42-year-old man who presented for a primary shoulder arthroplasty.
Fig. 1-A Results of the culture of a specimen from the unprepared skin surface. Combining the culture positivity for the 2 different species of Propionibacterium yielded an SpPV of 2.
Note that, despite the presence of these bacteria, the Gram smear was negative.
Fig. 1-B Results of the culture of a specimen from the freshly incised dermis. The SpPV was 3.
Fig. 1-C Results of the culture of the control swab. TheSpPVwas 0.

Results: The skin-surface SpPV was greater than 1 in 3 (17%) of the 18 female patients and in 34 (71%) of the 48 male patients (p <0.001).

The dermal SpPV was greater than 1 in 0 (0%) of the 18 female patients and in 19 (40%) of the 48 male patients (p < 0.001).

None of the control samples had an SpPV greater than 1.   The predictive characteristics of a skin-surface SpPV of greater than 1 for a dermal SpPV of greater than 1 were as follows: sensitivity, 1.00 (95% confidence interval [CI], 0.82 to 1.00); specificity, 0.62 (95% CI, 0.46 to 0.75); positive predictive value, 0.51 (95% CI, 0.34 to 0.68); and negative predictive value, 1.00 (95% CI, 0.88 to 1.00).

The authors concluded that preoperative culture of the unprepared skin surface can help to predict whether the freshly incised dermal edge is likely to be positive for Propionibacterium. This test may help to identify patients who may merit more aggressive topical and systemic antibiotic prophylaxis.

They also point out the value of semiquantitative culture reported in understanding the significance of culture results.

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We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art" regarding this radically conservative approach to shoulder arthritis at this link and this link

Use the "Search" box to the right to find other topics of interest to you.

How you can support progress in shoulder surgery

You may be interested in some of our most visited web pages arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'