Propionibacterium Acnes in Shoulder Arthroplasty

Over half of all post-operative infections after shoulder arthroplasty are due to
Propionibacterium acnes. Even in apparently "aseptic" revisions, nearly all cultures taken at
the time of revision surgery are positive for P acnes, and thus low-grade infection with this
bacteria may be a more common cause of failure than previously suspected. Current antibiotic
prophylaxis methods are ineffective against P acnes. Despite intravenous cefazolin, P acnes
can be cultured from the glenohumeral joint in 42% of patients undergoing primary total
shoulder arthroplasty. Despite skin preparation with chlorhexidine, P acnes can be cultured
from 73% of portal sites in arthroscopy. P acnes is further insensitive to alcohol.
Dermatologists have long been treating P acnes as it is a primary cause of acne vulgaris. One
of the most popular and effective treatments for acne vulgaris is topical benzoyl peroxide. A
prior prospective clinical trial demonstrated that adding topical 5% benzoyl peroxide 48
hours prior to surgery reduced P acnes culture positivity to 6%. The downside of this
treatment is that it must be applied by the patient, at home, for 48 hours prior to surgery.
An additional downside is that benzoyl peroxide is a skin irritant that not all patients
tolerate.

In aqueous environments, benzoyl peroxide rapidly decomposes into benzoic acid and hydrogen
peroxide. Benzoic acid is a skin irritant and hydrogen peroxide is the active ingredient.
Benzoyl peroxide is used instead of hydrogen peroxide because hydrogen peroxide breaks down
into water and oxygen when exposed to light. Recently, stabilized forms of hydrogen peroxide
have been developed and have been demonstrated to be equally effective to benzoyl peroxide in
the treatment of acne vulgaris. One potential reason for hydrogen peroxide's efficacy against
P acnes is that it is absorbed into the skin, addressing P acnes residing in sebaceous
glands. To date, no studies have examined whether the addition of hydrogen peroxide to
pre-operative skin preparation can reduce intra-operative P acnes culture positivity.

Inclusion Criteria:

- Patients undergoing primary shoulder arthroplasty

Exclusion Criteria:

- Patients with prior shoulder surgery.

- Patients with a symptomatic infection or history of infection, recent antibiotic use
(within six weeks), or with clinical signs of infection such as an elevated ESR, CRP,
positive aspiration cultures, or positive biopsy.

- Patients with a known hypersensitivity to hydrogen peroxide.