Periprosthetic infection following shoulder arthroplasty is a devastating complication. Infected shoulder arthroplasty not only causes an unexpected health hazard to patients but also imposes a heavy financial burden at both individual and societal levels. The rates of periprosthetic shoulder infection (PSI) have been reported to be 0.80% to 1.46%, but the number of infections is likely to increase as shoulder arthroplasty becomes more commonplace in an aging active population. Diagnosing and treating PSI poses a significant challenge. Unlike periprosthetic infection in other joints, PSI lacks the typical clinical signs and laboratory findings of infection due to the indolent nature of the offending pathogens. At the forefront of this issue is Cutibacterium acnes. Although the typical Staphylococcus, Streptococcus, and Corynebacterium species that reside on the skin surface are the primary targets of most surgical infection prophylaxis regimens, C acnes has emerged as a problematic bacterium because the current prophylactic regimens are insufficient to eradicate C acnes from the surgical field.

C acnes is one of the most common pathogens of infections after shoulder surgery. It is a commensal, gram-positive anaerobic bacillus that resides in the sebaceous glands associated with hair follicles. The colonization with C acnes of the front and back side of the shoulder epidermis is greater than that of other regions of the body because of the high density of the sebaceous glands in that area. C acnes can cause low-grade infections after shoulder surgery, and it has been shown that it is the most commonly detected bacterium after revision shoulder arthroplasty surgery. During revision shoulder arthroscopy cases performed for pain, stiffness, or weakness, 30% of patients had positive culture findings, and 80% of those findings were positive for C acnes. It is believed that C acnes infections occur during surgery when the sebaceous glands in the skin are cut and exposed, leading to C acnes contaminating the surgeon's instruments and gloves and, thus, the surgical wound. Recent studies showed that hydrogen peroxide and benzoyl peroxide were more effective than the conventional skin preparation methods in decreasing the C acnes load in the skin, but as high as 17% of the cultures were still positive for C acnes even with these new measures. Thus, despite all the efforts to eradicate C acnes from the shoulder, C acnes remain an elusive pathogen that is potentially contaminating tens of thousands of shoulder arthroplasties each year.

Surgical diathermy (or electrocautery) has been used routinely for tissue dissection and hemostasis during surgical procedures. In the cutting mode, the use of an electrode delivering a pure continuous sinusoidal wave of low voltage produces as high temperatures as 1000℃, which heats cells within the tissue so rapidly that they vaporize, leaving a cavity within the cell matrix. The heat created dissipates as a stream rather than being transmitted into adjacent tissues. This allows tissue cleavage without damage to surrounding areas. The electrode does not need to be in contact with tissue as an arc is formed producing a clean cut. With the coagulation mode on high power, cutting also occurs, but this produces a larger zone of greater thermal damage. Electrocautery can be used for dissecting fascia and muscle layers, as well as achieving hemostasis, and it has become an integral part of modern surgical practice. A number of clinical studies evaluated the safety and efficacy of cutting electrocautery for surgical incisions in general, plastic, otorhinolaryngological, orthopedic, neurosurgical, and gynecologic procedures. Additionally, systematic reviews and meta-analyses were conducted for the same purposes. The majority of these studies showed that using electrocautery to cut the skin provided the benefits of reduced bleeding, a quicker incision, and decreased postoperative pain with no increase of wound complications when compared to scalpel incisions. Given the high temperatures generated at the tip of an electrode of electrocautery, it is reasonable to assume that making a skin incision with electrocautery could potentially destroy exposed colonies of C acnes in hair follicles and sebaceous glands open on the incisional surface of the skin. The purpose of this study is to examine if making skin incisions using electrocautery will result in decreased C acnes contamination during shoulder arthroplasty. To this end, we propose a randomized clinical trial where patients undergoing shoulder arthroplasty are randomized into two groups - Electrocautery incision group (Electro) vs. Scalpel incision group (Scalpel) - and swab cultures are obtained from the skin incision and operating surgeon's gloves and forceps.