The effect of pretreatment of the pilosebaceous unit on Cutibacterium acnes burden during shoulder arthroplasty: a...

Cutibacterium acnes (C. acnes) is the most common pathogen associated with prosthetic shoulder infection and can be cultured from the surgical field, with a reservoir is in the pilosebaceous unit. Benzoyl peroxide (BPO) and blue-light phototherapy (BLT) are commonly used to target the pilosebaceous reservoir of C. acnes in the treatment of acne vulgaris. The aim of this study is to evaluate the effect of targeted pretreatment of pilosebaceous unit on C. acnes culture positivity within the surgical field during shoulder arthroplasty. We tested two hypotheses: 1) combination therapy is required to decrease overall C. acnes burden and 2) superficial culture positivity on the approach is associated with deep culture positivity, collected before closure.

A prospective, multicenter, randomized controlled trial was initiated across two sites and three shoulder arthroplasty study arms were recruited: 1) control: standard preparation; 2) BPO group: 2 days of 10% BPO wash preparation in the shower prior to surgery; and 3) BPO and BLT: 2 days of BPO washes with 3 preoperative treatments of blue spectrum phototherapy daily. Two specimens were taken at the surgical approach (full thickness incisional skin biopsy and superficial dermal swab) and a deep glenohumeral swab was taken prior to closure.

Following an a priori analysis, 122 patients were enrolled in the study, (41 controls, 41 BPO, and 40 BPO/BLT). No adverse side effects were reported. Demographic characteristics did not differ between treatment groups. Overall culture positivity was decreased in the BPO/BLT group compared to the control (13.3% vs. 26.8%, P = 0.026), odds ratio 0.420, 95% confidence interval [0.217, 0.812], P < 0.001. There was no difference between intervention groups: BPO/BLT and BPO (13.3% vs. 16.5%, P > 0.999). Superficial culture positivity on the approach (full-thickness biopsy and superficial swab) was associated with deep culture positivity at closure (P < 0.001). Otherwise, overall culture positivity was associated with male sex (P < 0.001), increasing height (P < 0.001), and decreased body mass index (P = 0.0235).

Targeted pretreatment of the pilosebaceous unit with combination BPO wash and BLT decreased C. acnes culture positivity within the surgical field. Positive superficial cultures on the approach were associated with positive deep cultures collected before closure. Ultimately, it is hoped that a decrease in C. acnes burden in the surgical field will positively impact the incidence of shoulder prosthetic joint infection.