Joint replacement is becoming an increasingly common procedure. In 2005, 534,000 total knee arthroplasties (TKA) were performed in the United States which is at a rate of 18.1 per 10,000 individuals, and the demand for primary TKA is projected to grow by 673% by 2030. Effective post-operative analgesia is an important component with regards to patient satisfaction and hospital stay. Regional anesthesia has been shown to decrease duration of surgery, need for transfusion, post-operative nausea and vomiting, and the incidence of thromboembolic disease in patients undergoing total knee or total hip replacement when compared with general anesthesia. Post-operatively, regional anesthesia has been shown to reduce pain scores and/or morphine consumption as well as opioid-related adverse effects.

Epidural catheter or spinal anesthesia has become the standard of care at the University of Wisconsin-Madison for intraoperative management of TKA patients. General anesthesia is still occasionally used for patients that would strongly prefer a general anesthetic, those that are taking anticoagulation medications or with a coagulopathy, those with previous back surgery, and those with certain neurologic conditions such as multiple sclerosis or spina bifida. Comparison studies between lumbar epidural analgesia and femoral nerve catheters (FNC) for postoperative analgesia following TKA show no significant difference in pain scores, morphine consumption, or post-operative nausea and vomiting. However, epidural analgesia has been associated with higher incidence of hypotension and urinary retention. FNC's placed for postoperative pain allow patients to ambulate more effectively as there should not be much of a lower extremity motor block. Patients with a FNC for postoperative analgesia also do not require a urinary catheter which eliminates a common source of infection in postoperative patients. FNCs have also demonstrated improved rehabilitation times and decreased hospital stays which has led to an increased insertion rate of FNCs for postoperative analgesia following TKA at the University of Wisconsin.

Pyarthrosis is a fairly common complication occurring at a rate of 2% following primary and 5.6% following revision TKA. Infection can be a devastating complication following implantation of joint hardware often leading to extended hospitalization/rehabilitation stays and return trips to the operating room. The average billed charges for all types of revision TKA procedures was $49,360 with average length of stay of 5.1 days. Indwelling lines are a known infection risk and indwelling lines in the femoral region are known to be associated with a high incidence of catheter colonization. At 48 hours, Cuvillon et. al. found that 57% of FNCs placed without the use of a chlorhexidine impregnated patch had positive bacterial colonization. They also described three cases of transient bacteremia secondary to FNCs in the 208 catheters that they analyzed.

Chlorhexidine impregnated patches also known as "biopatches" have been shown to reduce the incidence of bacterial colonization and infection of various indwelling lines including epidurals and central venous catheters. Currently no standard of care exists that requires the use of biopatches for FNCs. The investigators propose studying the use of the biopatch to reduce the incidence of bacterial colonization of femoral nerve catheters.

The investigators will study the efficacy of the biopatch at decreasing the rate of bacterial colonization of FNCs in TKA patients. The FNCs will be inserted in the standard fashion and removed at the end of therapy. Typically the FNC infusion will continue until the morning of post-operation day (POD) #1 or 2. The process for FNC insertion first involves sterile prep and drape of the femoral region. Full sterile technique will be utilized including gown, gloves, and mask. Ultrasound guidance is then commonly utilized to identify the femoral nerve. Following patient sedation and skin infiltration with local anesthetic, a tuohy needle is inserted adjacent to the femoral nerve. A catheter is then threaded through the needle in close proximity to the femoral nerve. Patients will be randomized to either no chlorhexidine impregnated patch or to a chlorhexidine impregnated patch that will be located at the catheter exit site. On the morning of POD 1 or 2, the FNC infusion will be discontinued. Typically, Twenty-four to forty-eight hours after catheter insertion, it will be removed in a sterile fashion and the skin surrounding the catheter exit site will be swabbed and the distal catheter tip will be sent for culture to determine bacterial colonization. In addition, the investigators will interview patients and review clinical data to determine signs of infection and/or catheter tip colonization rates.

Inclusion Criteria:

• Patients age 18-85 undergoing elective knee arthroplasty who elect to have a femoral nerve block catheter placed for postoperative analgesia.

Exclusion Criteria:

• Allergy to local anesthetics,
• local or generalized infection or inflammation,
• current antibiotic therapy,
• immunocompromised patients,
• a history of chronic steroid use,
• neurological deficits,
• pregnancy,
• prisoners,
• refusal to participate,
• primary language other than English,
• and patients currently participating in a study.