Conditions: Propionibacterium Acnes
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 50
Healthy volunteers: no

Brief summary:
This is a randomized trial of benzoyl peroxide soap versus Hibiclens soap for surgical preparation. The objective is to determine whether benzoyl peroxide soap, commonly available in drug stores for over-the-counter acne treatment, is as or more effective than the standard surgical preoperative soap, Hibiclens soap (chlorhexidine gluconate), in reducing loads of Propionibacteria (Propi) on or under the skin of patients prior to shoulder arthroplasty (joint replacement).

Detailed description:

Arms:
arm 1: None arm 2: None

Interventions: intervention 1: Benzoyl Peroxide 10% Bar intervention 2: Chlorhexidine Gluconate
Intervention descriptions: intervention 1: Patients will wash with Benzoyl Peroxide 10% Bar intervention 2: Patients will wash with Chlorhexidine Gluconate

Protocol document:
Prot_SAP_000.pdf: 
Randomized Trial of Hibiclens vs Benzoyl Peroxide Soap for Surgical Preparation 
NCT04021524 
Study Protocol and SAP 
5/8/2020 
 
 


Study Protocol 
Adult male patients planning to undergo shoulder arthroplasty were assessed for 
eligibility by a research coordinator at their pre-operative appointment in the clinic. The 
study was confined to male patients because of their higher risk of Cutibacterium 
periprosthetic infections. Exclusion criteria were as follows: (1) self-reported skin 
sensitivity, (2) reported sensitivity or allergy to either chlorhexidine or benzoyl peroxide, 
(3) use of antibiotics within three months of surgical date, (4) use of medication for acne 
within three months of surgical date, and (5) lack of fluency in the English language. 
Patient age, sex, American Society of Anesthesiologist (ASA) classification, body mass 
index (BMI), and history of previous surgery on ipsilateral shoulder were recorded.  
The patients were randomized by a research coordinator using simple randomization 
implemented through REDCap. The first group received a bottle of 4% chlorhexidine 
gluconate solution (CHG group). The second group received a bar of 10% benzoyl 
peroxide soap (BPO group). Both the chlorhexidine solution and benzoyl peroxide soap 
were stocked in the clinic so that all patients in each group received the same 
preparation. Both groups were instructed to apply the wash or soap to the surgical 
shoulder the night prior and the morning of surgery and to scrub for at least 60 seconds 
with the wash. The treating surgeon and all care providers were blinded to treatment 
group throughout the patient’s care.  
In the operating room, the unprepared, unshaved skin surface was sampled with a swab 
(Eswab™, #480C, Copan Diagnostics, Inc., Murrieta, CA) in the area of the planned 
incision. Four passes with the swab were taken by a surgical assistant wearing sterile 
gloves, turning the swab 90 degrees for each pass. The skin was then prepared with 
dual application of 2% CHG in 70% isopropyl alcohol and administration of intravenous 
antibiotics. Immediately after skin incision, swabs of the dermal wound edge were 
obtained in a similar fashion to the skin surface.  
All specimens were processed by the laboratory in a Class 2 laminar flow biological 
safety cabinet. Specimens were inoculated onto the following microbiological media: 
blood agar (trypticase soy agar with 5% sheep blood), chocolate agar, Brucella agar 
(with blood, hemin, and vitamin K), and brainheart infusion broth. All media, with the 
exception of the Brucella agar, were incubated at 37 °C with 5% CO2 for 21 days. 
Brucella agar plates were incubated anaerobically at 37 °C for 21 days. Plates were 
sealed in a manner that allows sterile aeration without desiccation. Media were 
examined daily for growth visually but were only opened if growth was noted.  
The cultures results were reported in a semiquantitative manner as the Specimen 
Cutibacterium Value (SpCuV) across a range of 0 (no growth) to 4 (4+ positive growth 
on agar plates). 
 
 


SAP 
An a priori sample size calculation was performed using previous data regarding growth 
of Cutibacterium from the skin of shoulder arthroplasty patients. Based on pilot data 
combined with previous published data, we estimated the incidence of positive 
Cutibacterium cultures on the skin surface of male patients to be 77%. We determined 
the sample size of 50 was necessary to detect a reduction of 50% between the two 
groups with 1:1 allocation ratio, a power of 0.80, and an alpha of 0.05. Given that the 
intervention and outcome were only separated by 1 day, we anticipated a 0% dropout 
rate. Baseline demographics were compared between groups using a t test for 
continuous variables and a chi-square test for categorical variables. The two groups 
were compared with regards to the percent positivity of the skin surface and incised 
dermal edge as well as the bacterial load at each site using a chi-square test. 
 
 

ICF_001.pdf: 
Randomized Trial of Hibiclens vs Benzoyl Peroxide Soap for 
Surgical Preparation 
 
NCT04021524 
 
8/7/2018 


Approved 
8/7/2018 
STUDY00005028 Consent Form 
Version 2018-08-07 
1 of 3 
 
 
UW HSD IRB 
UNIVERSITY OF WASHINGTON 
CONSENT FORM 
 
RANDOMIZED TRIAL OF HIBICLENS VS BENZOYL PEROXIDE SOAP FOR SURGICAL PREPARATION 
 
 
Researchers: Principal 
Investigator: Frederick A. 
Matsen III, MD 
University of Washington, Dept. of Orthopaedics 
206-543-3690 
matsen@uw.edu 
 
Study Coordinator: 
Anastasia J. Whitson 
University of Washington, Dept. of Orthopaedics 
206-437-9695 
ShoulderResearch@uw.edu 
 
24-hour Contact Number:  If you need to speak to someone right away, 
call the UWMC Paging Operator at (206) 598-6190 and ask to speak to the on-call shoulder fellow. 
 
 
Researchers’ statement 
We are asking you to be in a research study. The purpose of this consent form is to give you the information you 
will need to help you decide whether to be in the study or not. Please read the form carefully. You may ask 
questions about the purpose of the research, what we would ask you to do, the possible risks and benefits, your 
rights as a volunteer, and anything else about the research or this form that is not clear. When we have answered 
all your questions, you can decide if you want to be in the study or not. This process is called “informed consent.” 
We will give you a copy of this form for your records. 
 
PURPOSE OF THE STUDY 
Propionibacteria (Propi) are bacteria often found in failed joint replacement surgeries. While these bacteria are 
commonly found on normal skin, many doctors think they cause problems that make it hard for a patient to heal 
after surgery, especially for male patients. Patients having shoulder replacement surgery at UW are typically 
instructed to wash with Hibiclens, a liquid soap with the active ingredient chlorhexidine gluconate, before arriving 
at the hospital on the day of surgery. The goal of washing your skin with this specialized soap before surgery is to 
lower the chance that the normal skin bacteria would enter the shoulder wound at the time of surgery. A soap bar 
with the active ingredient benzoyl peroxide (BPO) is a commonly available over-the-counter treatment for acne. 
Acne can be caused by the same Propi bacteria that the Hibiclens soap is trying to get rid of. The BPO soap may 
be used in the same way as the Hibiclens soap to wash your skin at home before surgery. We would like to better 
understand whether the BPO soap is as or more effective than the Hibiclens soap in lowering the amount of Propi 
in the skin of patients before a shoulder joint replacement. 
 
STUDY PROCEDURES 
If you choose to be in this study, you will be randomized into one of two groups. One group will use the BPO soap 
and the other group will use the Hibiclens soap to wash their skin the night before and morning of surgery. The 
group you will be in is decided by chance, like the flip of a coin, once you join this study. You have an equal 
chance of being placed in either group. 
 
We will supply you with the soap and a washing instruction sheet. The clinic nurse will also discuss the washing 
instructions with you. These are the same instructions you would get if you did not join the study and were 
washing with the Hibiclens soap before surgery, as all patients getting shoulder replacement surgery at UW are 
instructed to do. We may call you a few days before surgery to remind you about using the soap and ask if you 
have any questions. 
 
During surgery, samples of your bacteria are routinely taken and cultured to learn what bacteria are living in and 
on your skin. This study will not require that any additional samples to be taken; instead, we will use the results 
from the samples taken for your clinical treatment. 
 
We may obtain the following information from your medical records at the University of Washington Medical 
Center, Harborview Medical Center, and/or Northwest Hospital: 
Demographics: birthdate, age, gender, race, ethnicity, height, weight, handedness, marital status 


Approved 
8/7/2018 
STUDY00005028 Consent Form 
Version 2018-08-07 
2 of 3 
 
 
UW HSD IRB 
 
Symptoms and clinical history: medical and surgical history, clinical family history, allergies, 
medications, diagnoses, culture results, any X-rays or radiographic images and treatments 
 
RISKS, STRESS, OR DISCOMFORT 
We expect the risk of side effects of both soaps to be low. There is a risk of discomfort or irritation from the active 
ingredients in either of the soaps, including possible redness, burning, itching, peeling, or possibly swelling. Risks 
will be reduced by asking you in advance if you are sensitive to those ingredients; if so, you will not be eligible to 
participate in this study. The risks between the two soaps are very similar. 
 
In the event that you experience severe irritation, you should contact us at the 24-hour number listed at the top of 
this consent form. 
 
There is a risk of hair, towels, or clothing being bleached if they make contact with the soap. 
 
There is a risk that the soap could make your skin sensitive to irritation from the sun. To minimize this risk, avoid 
spending time in the sun before surgery. 
 
Infection of the shoulder after surgery can happen when bacteria, like Propi, enter the joint and remain there, 
causing problems of pain, stiffness and loosening of the joint replacement. There is the same amount of risk for 
infection after surgery whether you use the BPO soap or the Hibiclens soap. If you join this study, you will receive 
the same care to help lower the risk of infection at the time of surgery as you would if you did not join. 
 
There is a potential risk of loss of confidentiality by participating in this research study. Every effort will be made to 
keep information confidential; however, this cannot be guaranteed. Information in your medical record will be used 
for research purposes, and the study team will have access to this information. Some people do not want 
information from their medical records used for research. If you feel this way, you should not be in this study. 
More information on confidentiality and privacy is provided below. 
 
ALTERNATIVES TO TAKING PART IN THIS STUDY 
If you do not choose to participate in this study, you will not be assigned to one soap randomly. You will be given 
the soap currently used for surgical preparation, which is Hibiclens, in accordance with our clinical practice. 
 
BENEFITS OF THE STUDY 
You will not benefit directly from taking part in this study. We hope that the results of this research will benefit 
society at large by contributing to prevention of surgical infections and associated complications in the future. If 
you decide not to participate in this study, you will still receive soap at your pre-operative appointment free of 
charge. 
 
SOURCE OF FUNDING 
There is no external funding or support for this research. 
 
CONFIDENTIALITY OF RESEARCH INFORMATION 
The link between your identifiers and the research data will be destroyed after the records retention period 
required by state and/or federal law. 
 
Government or university staff sometimes review studies such as this one to make sure they are being done 
safely and legally. If a review of this study takes place, your records may be examined. The reviewers will protect 
your privacy. The study records will not be used to put you at legal risk of harm. 
 
OTHER INFORMATION 
You may refuse to participate, and you are free to withdraw from this study at any time without penalty or loss of 
benefits to which you are otherwise entitled. 
 
RESEARCH-RELATED INJURY 
If you think you have a medical problem or illness related to this research, contact Dr. Frederick Matsen at (206) 
543-3690 right away. He will treat you or refer you for treatment. 


Approved 
8/7/2018 
STUDY00005028 Consent Form 
Version 2018-08-07 
3 of 3 
 
 
UW HSD IRB 
Subject’s statement 
This study has been explained to me. I volunteer to take part in this research. I have had a chance to ask 
questions. If I have questions later about the research, or if I have been harmed by participating in this study, I 
can contact one of the researchers listed on the first page of this consent form. If I have questions about my rights 
as a research subject, I can call the Human Subjects Division at (206) 543-0098 or call collect at (206) 221-5940. 
I give permission to the researchers to use my medical records as described in this consent form. I will receive a 
copy of this consent form. 
 
 
 
Printed name of subject 
Signature of subject 
Date 
 
 
 
Copies to:   Researcher 
Subject