Efficacy of Surgical Preparation Solutions in Foot and Ankle Surgery

Ostrander, Roger V. MD; Botte, Michael J. MD; Brage, Michael E. MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.D.01977
Scientific Articles
Abstract

Background: Previous studies have demonstrated higher infection rates following orthopaedic procedures on the foot and ankle as compared with procedures involving other areas of the body. Previous studies also have documented the difficulty of eliminating bacteria from the forefoot prior to surgery. The purpose of the present study was to evaluate the efficacy of three different surgical skin-preparation solutions in eliminating potential bacterial pathogens from the foot.

Methods: A prospective study was undertaken to evaluate 125 consecutive patients undergoing surgery of the foot and ankle. Each lower extremity was prepared with one of three randomly selected solutions: DuraPrep (0.7% iodine and 74% isopropyl alcohol), Techni-Care (3.0% chloroxylenol), or ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol). After preparation, quantitative culture specimens were obtained from three locations: the hallux nailfold (the hallux site), the web spaces between the second and third and between the fourth and fifth digits (the toe site), and the anterior part of the tibia (the control site).

Results: In the Techni-Care group, bacteria grew on culture of specimens obtained from 95% of the hallux sites, 98% of the toe sites, and 35% of the control sites. In the DuraPrep group, bacteria grew on culture of specimens obtained from 65% of the hallux sites, 45% of the toe sites, and 23% of the control sites. In the ChloraPrep group, bacteria grew on culture of specimens from 30% of the hallux sites, 23% of the toe sites, and 10% of the control sites. ChloraPrep was the most effective agent for eliminating bacteria from the halluces and the toes (p < 0.0001).

Conclusions: The use of effective preoperative preparation solution is an important step in limiting surgical wound contamination and preventing infection, particularly in foot and ankle surgery. Of the three solutions tested in the present study, the combination of chlorhexidine and alcohol (ChloraPrep) was most effective for eliminating bacteria from the forefoot prior to surgery.

Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Author Information

1 Andrews Orthopaedic and Sports Medicine Center, 1118 Gulf Breeze Parkway, Suite 100, Gulf Breeze, FL 32561

2 Division of Orthopaedic Surgery, Scripps Clinic and Research Foundation, 10666 North Torrey Pines Road, La Jolla, CA 92037

3 Department of Orthopaedics, University of California, San Diego, 200 West Arbor Drive, #8894, San Diego, CA 92103

Article Outline

Previous studies have demonstrated higher infection rates following orthopaedic procedures involving the foot and ankle as compared with those involving other areas of the body1-7. Previous studies also have documented the difficulty of eliminating bacteria from the forefoot prior to surgery8-11. Although multiple factors affect postoperative infection, the unique anatomy of the foot and its resident organisms may play a role in the higher infection rates seen following foot and ankle surgery. Use of an effective preoperative preparation solution is an important step in limiting surgical wound contamination and in preventing infection. The purpose of the present study was to assess the efficacy of three different surgical skin-preparation solutions in eliminating potential bacterial pathogens from the foot by evaluating the residual bacterial skin contamination following surgical skin preparation.

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Materials and Methods

The present prospective, randomized study included 125 consecutive patients undergoing surgery of the foot and ankle between October 2002 and May 2003. All procedures were performed by one surgeon (M.E.B.). Patients were excluded if they had an open wound, abrasion, or current infection. The study included forty-seven men and seventy-eight women with a mean age of forty-eight years (range, nineteen to seventy-eight years). Each lower extremity was prepared, according to the manufacturer's instructions, with one of three randomly selected solutions: DuraPrep (0.7% iodine and 74% isopropyl alcohol) (3M Healthcare, St. Paul, Minnesota), Techni-Care (3.0% chloroxylenol) (Care-Tech Laboratories, Saint Louis, Missouri), or ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol) (Medi-Flex, Overland Park, Kansas). Treatment allocation was achieved by using the solutions in a consistent order throughout the study period. The preparation was performed by well-trained members of the operating-room staff who were not involved in the study. No home cleansing or disinfection protocols were utilized prior to surgery. Forty patients were included in each of the three surgical preparation groups (see Appendix). Overall, the patient population was healthy. In the DuraPrep group, four patients had rheumatoid arthritis, one patient had diabetes mellitus, one patient had renal failure, and two patients had liver disease. In the Techni-Care group, two patients had rheumatoid arthritis, two patients had liver disease, and one patient had renal insufficiency. In the ChloraPrep group, two patients had rheumatoid arthritis, one patient had end-stage renal disease, and one patient had undergone a renal transplantation.

Culture specimens were obtained in an identical fashion from five additional subjects (the Pre-Prep Group) immediately before surgical preparation. This was done to quantitate the normal amount of skin bacteria present prior to treatment with an antibacterial surgical scrub.

All patients received a preoperative dose of an antibiotic (1 g of intravenously administered cefazolin) within one hour before the surgical start time. After preparation and draping were complete, quantitative culture specimens were obtained from three locations on the foot and ankle. Separate cotton-tipped applicators were used at each of the three locations to obtain the culture specimens. The first specimen was taken from the anterior part of the tibia, 12 cm proximal to the ankle joint. This site was used as the control site because we are not aware of any documented problems with regard to the elimination of skin bacteria or with regard to high rates of postoperative infection in this region. The second specimen was taken along the hallucal nail fold, which subsequently was referred to as the hallux site. The third specimen was taken from the web spaces between the second and third and between the fourth and fifth digits, which subsequently was referred to as the toe site. The swabs were placed into Amies transport media (Becton Dickinson, Franklin Lakes, New Jersey) and were sent immediately to the microbiology laboratory for quantitative aerobic and anaerobic culture.

The culture swabs were placed into 1 mL of brain-heart infusion broth and were vortexed. Next, 0.025 mL of the specimen broth was inoculated onto rabbit blood agar, colistinnalidixic acid agar, and eosin-methylene blue agar and into thioglycolate broth (for aerobic culture) or Schaedler broth (for anaerobic culture). All culture media were supplied by Beckton Dickinson (Sparks, Maryland). The aerobic specimens were incubated in 5% carbon dioxide atmosphere at 35°C. The plates were read at twenty-four and forty-eight hours before a final report was issued. The anaerobic plates were incubated in an anaerobic chamber at 35°C. The plates were read daily, and a final report was issued at seven days. The colony count on each plate was determined and multiplied by 40 to calculate the number of colony-forming units per mL. All plates were read and counted manually by a laboratory technician who was not involved in the study. If any growth was detected, the sample was considered positive. Colony-forming units are referred to as “colonies” for simplicity. The term “bacterial isolate” is used to refer to a bacterial strain, including different strains of the same bacterial species.

The present study was reviewed and approved by our institutional review board.

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Statistical Analysis

Data were analyzed with use of two-way analysis of variance with position (control, hallux, or toe site) and treatment (ChloraPrep, DuraPrep, or Techni-Care) as grouping variables. Data were first screened for normality to justify the use of parametric statistics. As a result of the high skew, data were log-transformed, which dramatically decreased skew and kurtosis values to normal levels. Post hoc tests for comparisons between groups were performed with use of the Fisher protected least-squares-difference test.

Chi-square analysis was used to evaluate the difference in culture rates between the study groups and the different culture locations.

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Results

In the Pre-Prep group, bacteria grew on culture of specimens obtained from 100% of the hallux sites, 100% of the toe sites, and 100% of the control sites. In the Techni-Care group, bacteria grew on culture of specimens obtained from 95% (thirty-eight) of the hallux sites (with eighty-three total bacterial isolates and 145,500 total colonies), 98% (thirty-nine) of the toe sites (with eighty-five total bacterial isolates and 188,360 total colonies), and 35% (fourteen) of the control sites (with twenty total bacterial isolates and 6000 total colonies) (Fig. 1, Table I). In the DuraPrep group, bacteria grew on culture of specimens obtained from 65% (twenty-six) of the hallux sites (with forty-eight total bacterial isolates and 49,400 total colonies), 45% (eighteen) of the toe sites (with twenty-seven total bacterial isolates and 27,480 total colonies), and 23% (nine) of the control sites (with eleven total bacterial isolates and 4960 total colonies). In the ChloraPrep group, bacteria grew on culture of specimens obtained from 30% (twelve) of the hallux sites (with eighteen total bacterial isolates and 10,200 total colonies), 23% (nine) of the toe sites (with thirteen total bacterial isolates and 10,880 total colonies), and 10% (four) of the control sites (with four total bacterial isolates and 160 total colonies).

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.

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Discussion

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.

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Appendix

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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