Sterile stockinette in orthopaedic surgery: a possible pathway for infection

The prevention of infection in joint replacement surgery is important. Preparing and draping the patient is fundamental to maintaining sterility of the operative field. One method of draping for total knee replacement (TKR) surgery involves cleaning the operative leg with antiseptic wash then covering the un-prepped foot with a sterile stockinette to sequester the foot from the sterile field. There are two main methods for applying this stockinette. This randomized, blinded control trial simulates stockinette application to assess if it prevents proximal microbial migration into the sterile field.

To simulate microbial presence, ultraviolet fluorescent powder Glitterbug Powder™ (Arrow Scientific Pty Ltd, Lane Cove, NSW, Australia) was applied to volunteers' feet to the level where antiseptic wash would routinely stop during preparation. The stockinette was applied. Two methods of application (above and below knee) and two surgeons were used. These were randomized for each application. The drapes were removed and a blinded assistant measured the distance of proximal spread of Glitterbug Powder™.

Both methods of application were associated with considerable proximal spread of Glitterbug Powder™. For the below knee method, mean proximal spread distance of 49.19%; for the above knee, mean of 71.8% proximal spread (P = 0.038). Multivariate linear regression analysis demonstrated that method and location of the contamination were predictive of the area of contamination and the percentage of the leg contaminated. No other factors (surgeon, gender, hirsute score) were predictive of either area or percentage contamination.

The surgical field for TKRs may be contaminated by significant proximal microbial spread from the unprepared foot with the use of a sterile stockinette drape.