Knee arthroplasty continues to be one of the most common and successful methods for treating severe arthritis and other painful arthropathies. Increasing steadily from 1998 to 2008, and with more than 676,000 procedures performed in 2008, knee arthroplasty remains the most common surgical joint replacement procedure.1
Although perioperative and long-term complications are uncommon, infection remains one of the most serious complications of total knee arthroplasty (TKA). Some studies have found a post-TKA infection rate of less than 1%.2 The solution of 2% chlorhexidine gluconate and 70% isopropyl alcohol (Chloraprep; Medi-Flex, Overland Park, Kansas) is commonly used for antiseptic skin preparation before surgery. Studies have shown significant decreases in post-TKA infection rates with preoperative use.3,4 Another study evaluated the efficacy of 3 different skin solutions and found Chloraprep to be the most efficient in eradicating bacteria from the foot and ankle before surgery. The investigators noted that, even with preoperative use of Chloraprep, 23% of patients had residual bacteria on the surface of the skin between the toes.5 Like the foot, the popliteal fossa is an intertriginous area that may harbor normal flora, including gram-positive cocci, in large numbers, mainly because of the contact between 2 skin surfaces. Although postoperative infection rates decrease with use of Chloraprep, its presurgical efficacy in killing bacteria on another intertriginous area, the popliteal fossa, is largely unknown. Also unknown are susceptible organism species and organism population numbers.
Concerned that our skin preparation might be ineffective, we conducted a study to evaluate the efficacy of Chloraprep skin preparation in eradicating organisms before TKA, to isolate the type and number of organisms, and to evaluate several other contributing factors that could lead to infection.
Materials and Methods
This prospective study included 99 patients who were undergoing primary TKA at John Peter Smith Hospital between July 1, 2011 and August 31, 2012. An attempt was made to enroll consecutive TKA patients, and all patients agreed to participate, but a few were not enrolled because the study team had not asked for their consent before they were taken to the operating room. Patients did not receive monetary compensation for participation. Exclusion criteria were pregnancy, imprisonment, and age under 18 years. The study was approved by the institutional review boards at John Peter Smith Hospital and the University of North Texas Health Science Center.
Each lower extremity was prepared with Chloraprep according to the manufacturer’s instructions. Preparation was done by well-trained operating room staff members who were supervised by the surgeon (Dr. Sanchez or Dr. Wagner) but were not involved in the study. With use of the Chloraprep applicator, the solution was applied in a back-and-forth manner to the entire operative leg for at least 30 seconds, and then discarded. This scrub procedure was repeated with a second applicator before standard drapes were placed. The leg was left to air-dry for at least 30 seconds, and the drapes were placed before postsolution swabbing and before the iodine-impregnated adhesive drape was placed around the knee. During drying, the solution was not blotted, wiped away, or touched with instrumentation. Patients were swabbed with an epidermal sterile swab in the popliteal fossa of the knee undergoing surgery, both before solution application (presolution swab) and after (postsolution swab). Only the operating surgeon participated in swabbing the patients. Aerobic and anaerobic swabs were vigorously rubbed over a 2- to 3-in wide area across the entire posterior flexion crease surface.
The collected pre- and postsolution swabs were sent to John Peter Smith Laboratory for identification of organisms. Anaerobic swabs were cultured in thioglycolate broth and on 4 plates: MacConkey agar, Columbia colistin–nalidixic acid agar, chocolate agar, and sheep blood agar. Aerobic swabs were cultured in thioglycolate broth with hemin and vitamin K and on 4 plates: anaerobic blood agar, bile esculin agar, kanamycin and vancomycin agar, and Columbia colistin–nalidixic acid agar. Anaerobic plates were incubated in an anoxic environment. The plates were then read daily, and final reports were issued after 48 hours (for aerobic bacterial isolates) and 72 hours (for anaerobic bacterial isolates), as was the standard at the time.
Additional patient data were collected for possible correlations: American Society of Anesthesiologists (ASA) classification (physical status),6 body mass index (BMI), age, sex, arthroplasty type (unilateral, bilateral), and diabetic status. In addition, patients were asked if they had used Hibiclens antiseptic/antimicrobial skin cleanser daily during the week before surgery—as they had been instructed to do—and the number of times they had used the cleanser.
Study data were analyzed and were used to stratify patients into several groups. Each group had multiple factors evaluated.