Copyright © 2006 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Alexander Y. Shin, MD, and Dirk R. Larson, MS*,
Departments of Orthopedic Surgery (A.Y.S.) and Health Sciences Research (D.R.L.), Mayo Clinic, Rochester, Minnesota
The optimal treatment of external fixation pins has remained controversial because of the absence of prospective randomized studies comparing the various methods used to prevent pin-track infections. In 2004, Temple and Santy1 performed an evidence-based review of the literature on pin-site care and identified all randomized controlled studies of orthopedic pin care, of which thirteen were excluded on the basis of the authors' exclusion criteria. The single study that was included compared pin care with saline, a 70% alcohol solution, and no cleansing, and demonstrated significantly fewer infections in pins which had not been cleansed2.
Egol and coauthors sought to answer three questions related to the care of external fixation pins used in the treatment of distal radius fractures: (1) What is the prevalence of pin-track complications? (2) What is the frequency of antibiotic use and/or surgical débridement of infected pin tracks? and (3) Is there a reduction of pin-track infection when a commercially available chlorhexidine-impregnated disc is used in comparison with the use of daily hydrogen peroxide/saline cleaning and weekly dry dressings?
The authors prospectively randomized patients with distal radius fractures treated by external fixation to one of three groups (weekly chlorhexidine discs, daily hydrogen peroxide/saline cleaning, or weekly dry dressings), and evaluated them weekly for erythema, cellulitis, drainage, or radiographic loosening of the pins.
The overall prevalence of pin-related complications was 19% (twenty-three patients). The prevalence of pin-related complications was 18% for the sterile dry dressing group, 33% in the hydrogen peroxide/saline group, and 19% in the chlorhexidine group. The findings were reported as "no significant differences… noted among the three groups with regard to the rate of complications, with the numbers available." The authors also noted that age was a risk factor for an increased risk of pin-related complications, with 10% of patients receiving antibiotics.
Egol and coauthors should be applauded for their study, which challenges us to think about this problem anew. However, there are several concerns regarding the methodology and conclusions of the study. The power analysis performed prior to the initiation of the study was based on a report of a 21% prevalence of external fixation pin-track infections of the distal radius requiring treatment with oral antibiotics3. However, the prevalence of pin-track infections varies dramatically in the literature from a 1% prevalence of major infections to an 80% prevalence of minor infections4. Even in the study identified by the Cochrane review1, the prevalence of pin-track infection varied, based on treatment of pin sites, from 8% to 25%2. To estimate sample size for comparing rates, it is necessary to know both the baseline rate (i.e., the rate for the reference group or the null rate), as well as the difference to be detected. When a power analysis is performed on the basis of the 21% prevalence of pin-track infection as reported by Ahlborg and Josefsson3, then to have 80% power to detect a 5% decrease in one of the three groups being compared (i.e., 21% compared with 21% compared with 16%), 501 subjects per group (1,503 total) would be required5. A post-hoc power analysis performed with the result found in this study (19% compared with 33% compared with 18%) indicates that each group would require 115 patients. As such, this study is significantly underpowered.
A common factor in most studies of pin-site complications is the lack of a standard definition of what constitutes a pin-track complication. Is it inflammation around the pin site, which has been reported in up to 41.6% in one series6? Is it cellulitis about the pins, or pin sites with draining purulence, as suggested by other authors? Or is it loosening of the pins either clinically or radiographically? Surgeons who use external fixation have certainly noted pin sites to be erythematous, but is it a complication or an expected occurrence? The indications for administration of oral antibiotics have also not been clearly defined in this study or in clinical practice. In this study, 10% of patients (twelve patients) received antibiotics, yet the authors state that most complications in the study were erythema and local drainage, and these patients did not require antibiotics. The question that remains unanswered is: What are the indications for administration of antibiotics, and when should antibiotics be withheld?
Several authors have suggested that there are a number of factors associated with pin-track complications6. These include bone density, fracture type, and postoperative fracture stability; postoperative motion protocols; patient habitus; and comorbidities. These factors are difficult to control in a prospective, randomized study. It is clear that further investigation of pin-track care (with a concise definition of "pin-track complication" as well as clearly defined indications for antibiotic treatment) with sufficient power is needed to resolve the dilemma of the optimal treatment of pin-track sites.
*The author did not receive grants or outside funding in support of his research for or preparation of this manuscript. He did not receive 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 author is affiliated or associated.
References
1. Temple J, Santy J. Pin site care for preventing infections associated with external bone fixators and pins. Cochrane Database Syst Rev. 2004;1:CD004551.
2. Henry C. Pin sites: Do we need to clean them? Practice Nursing. 1996;7:12,15-17.
3. Ahlborg HG, Josefsson PO. Pin-tract complications in external fixation of fractures of the distal radius. Acta Orthop Scand. 1999;70:116-8.
4. Green SA. Complications of external skeletal fixation. Clin Orthop Relat Res. 1983;180:109-16.
5. Lachin JM. Sample size determinants for r X c comparative trials. Biometrics. 1977;33:315-24.
6. Mahan J, Seligson D, Henry SL, Hynes P, Dobbins J. Factors in pin tract infections. Orthopedics. 1991;14:305-8.
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