The positive culture rate associated with the hallux site in the ChloraPrep group was significantly lower than that in the DuraPrep group (p < 0.01), which was significantly lower than that in the Techni-Care group (p < 0.001). The positive culture rate associated with the toe site in the ChloraPrep group was significantly lower than that in the DuraPrep group (p < 0.05), which was significantly lower than that in the Techni-Care group (p < 0.001). The positive culture rate associated with the control site in the ChloraPrep group was not significantly different from that in the DuraPrep group (p < 0.2), but it was significantly lower than that in the Techni-Care group (p < 0.01). The positive culture rate associated with the control site in the DuraPrep group was not significantly different from that in the Techni-Care group (p < 1.0).
On the average, 4544 colonies were identified per culture in the Pre-Prep group, compared with 177 in the ChloraPrep group, 682 in the DuraPrep group, and 2833 in the Techni-Care group. All three treatment preparations were significantly different from one another with regard to the mean number of colonies per culture. ChloraPrep was associated with fewer bacterial colonies than DuraPrep (p < 0.0001), which was associated with fewer colonies than Techni-Care (p < 0.0001). With the numbers available, the Techni-Care group was the only group that was not significantly different from the Pre-Prep group (p < 0.09).
On the average, 4544 colonies were identified per positive culture in the Pre-Prep group, compared with 850 in the ChloraPrep group, 1544 in the DuraPrep group, and 3736 in the Techni-Care group. With the numbers available, the mean number of colonies per positive culture in the ChloraPrep group was not significantly different from that in the DuraPrep group (p < 0.2). The ChloraPrep group had significantly fewer colonies per positive culture than did the Techni-Care group (p < 0.0003) and the Pre-Prep group (p < 0.0004). The DuraPrep group also had significantly fewer colonies per positive culture than did the Techni-Care group (p < 0.0003) and the Pre-Prep group (p < 0.002). With the numbers available, the Techni-Care group was the only group that was not significantly different from the Pre-Prep group (p < 0.4).
With regard to the presence of residual bacteria following surgical preparation, there were highly significant differences among the different culture locations. In general, more bacteria were isolated from the hallux site compared with the control site (p < 0.001) and more bacteria were isolated from the toe site compared with the control site (p < 0.001). However, there was no significant difference between the toe site and hallux site (p > 0.05). With regard to specific solutions, ChloraPrep was the only solution that resulted in a positive culture rate at the toe site that was not significantly different, with the numbers available, from that at the control site (p < 0.2).
Of the 360 culture specimens that were obtained, 169 were positive for at least one organism. In many cases, multiple organisms grew on culture. Many potential aerobic and anaerobic pathogens were found (Fig. 2). Overall, 206 different bacterial isolates were identified, and, of these, 145 were identified as Staphylococcus epidermidis.
A postoperative infection developed in three patients, including two (5%) of the forty patients in the Techni-Care group and one (2.5%) of the forty patients in the ChloraPrep group. There were no infections in the DuraPrep group. With the numbers available, there was no significant difference among the three groups with regard to the postoperative infection rate (p < 1.0). In the Techni-Care group, one patient had development of a polymicrobial infection after open reduction and internal fixation of a calcaneal fracture. Cultures were positive for Pseudomonas, Staphylococcus epidermidis, Enterococcus, and Enterobacter. Staphylococcus epidermidis had grown on culture of post-preparation specimens, but the other organisms had not. The second patient in the Techni-Care group had development of an atypical mycobacterium infection after excision of a Morton neuroma. We had not tested for mycobacteria on cultures of the post-preparation specimens. One patient in the ChloraPrep group had development of a polymicrobial infection after excision of a large lipoma from the lateral aspect of the heel. A portion of the large tissue flap underwent necrosis, with subsequent development of infection. Cultures of the postpreparation specimens had been negative.
The findings of the present study are in agreement with those of previous studies that have shown that it is difficult to eliminate skin flora from the forefoot8-11. The foot provides a unique environment for the growth of numerous bacterial species. The skin surrounding the foot has many characteristics that differentiate it from other sites of the body. The lack of pilosebaceous units, the absence of apocrine sweat glands, and the wearing of occlusive footwear provide a unique habitat for microbes12,13. In addition, the presence of the nail, hyponychium, and nailfold provides a physical barrier to cleansing8. In a previous study, we found that potential bacterial wound pathogens grew on culture of specimens from 80% of halluces and 72% of toes following preparation with one of two randomly selected povidone-iodine-based antibacterial scrubs11. Neither of these preparations contained alcohol. Wolf et al.8 studied an iodine-based scrub and paint and reported that bacteria grew on culture of specimens obtained from 98% of halluces and 83% of toes. The findings of the current study suggest that the combination of iodine and alcohol is more effective than iodine alone.
The combination of chlorhexidine and alcohol was the most effective solution tested in the present study. The efficacy of chlorhexidine has been documented in a number of other studies. In a direct comparison of chlorhexidine, povidoneiodine, and chloroxylenol, Aly and Maibach found that chlorhexidine was significantly more effective for reducing bacterial counts from the hands14. With use of a dog model, Stubbs et al.15 found that chlorhexidine performed significantly better than chloroxylenol as a preoperative skin-preparation solution (p < 0.0001). Paulson16 evaluated five surgical hand-scrub preparations and found that the two chlorhexidine products achieved a significant reduction in microorganism counts (p < 0.001), with better residual effects, than either the iodine or chloroxylenol products did. The properties that make chlorhexidine effective include its strong affinity for binding to skin, its high level of antibacterial activity, and its prolonged residual effects17. In addition, its rapid activity has been found to surpass that of both povidone-iodine and chloroxylenol-containing solutions17.
There are numerous possibilities for further research. Different preparation techniques or solution combinations could be studied. However, one needs to consider the logistics of, and the surgeon's compliance with, the institution of more complicated protocols. Hort and DeOrio18 evaluated the use of a chlorhexidine home wash followed by preoperative preparation with iodine alone or iodine followed by alcohol. They found no significant difference between the two techniques. Brooks et al.10 reported that scrubbing of the toe clefts combined with the use of a standard preparation reduced the recolonization of bacteria in this area. Isolating the forefoot with an antibacterial-impregnated barrier may be a useful adjunct during procedures performed on the ankle, although this needs further study.
To our knowledge, this is the first study in which quantitative cultures have been used to document the efficacy of surgical scrub solutions in patients undergoing foot and ankle surgery. On the basis of these data, we can make assumptions regarding the ability of a surgical scrub solution to limit infection, although this effect is unproven. An ideal study would directly evaluate infection rates. Given the frequency of postoperative infection, such a study would require a much larger patient population to demonstrate a significant effect. There were three postoperative infections in the present study, including two in the Techni-Care group and one in the ChloraPrep group. The infection in the ChloraPrep group and one of the two infections in the Techni-Care group occurred following surgery over the lateral aspect of the calcaneus. Both of these infections developed as the result of wound-healing problems, which are well-known complications associated with surgery in this region given the thin soft-tissue envelope and tenuous blood supply19. We are not aware of any studies that have specifically evaluated the ability of a surgical scrub solution to reduce infection rates in patients undergoing foot and ankle surgery.
Another limitation of the present study is the fact that we did not obtain culture specimens from the foot of each patient prior to surgical preparation. It is possible that some individuals have a higher baseline bacterial load than others do. Culture specimens were obtained from five patients prior to surgical preparation. Cultures of specimens from all five patients demonstrated a substantial resident bacterial population.
For the purpose of the present study, we believed that using cotton-tipped swabs to sample the skin for bacterial culture, in the setting of a concomitant surgical procedure, was valid. Skin biopsy may be more accurate, but it is invasive and is associated with potential complications. Cotton-tipped swabs have been used to sample the skin on the foot and ankle in other similar studies in the literature8-11.
Performing a second set of cultures at a later point in time might have been useful. However, selecting a consistent time-interval to repeat the cultures would have been difficult because some procedures were completed in minutes whereas others lasted two to three hours. We believe that immediate cultures are most important in the clinical setting. If the surgical preparation solution is unable to reduce the bacterial load initially, then subsequent recolonization is irrelevant. Studies evaluating the pharmacokinetics of povidone-iodine and chloroxylenol have demonstrated good activity for more than three hours20,21. Similar research evaluating chlorhexidine has shown excellent activity for more than six hours17,22. All of the procedures in the present study lasted three hours or less.
In conclusion, given the higher rates of postoperative infection following foot and ankle surgery, every effort should be made to reduce the risk of infection in patients undergoing such procedures. The foot has a large resident microbial population and a unique anatomy, which make it difficult to eliminate skin bacteria preoperatively. In the present study, the combination of chlorhexidine and alcohol (ChloraPrep) was the most effective solution for eliminating potential wound contaminants from the forefoot prior to surgery.
Tables presenting clinical data on all 120 patients are available with the electronic versions of this article, on our web site at jbjs.org (go to the article citation and click on “Supplementary Material”) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM). ▪
NOTE: The authors thank Richard L. Lieber, PhD, for his statistical analysis and review.
In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Care-Tech Laboratories of St. Louis, Missouri, and Medi-Flex, Inc. of Overland Park, Kansas. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Department of Orthopaedics, University of California, San Diego, San Diego, California
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