Pin site infection is the most common complication and often a limiting factor associated with external fixators. Risk factors associated with pin site infection are poorly understood but most certainly multifactorial. Intrinsic (host, age, smoking etc.) as well as extrinsic (construct of fixator, duration of an applied external fixator, pin placement etc.) factors seem to affect the risk of pin site infection in a complex way.
Prevention seems to be of paramount importance tackling pin site infection. How to prevent infection optimally is thoroughly debated but several authors state that prevention starts in the operating theater with proper surgical technique. Aseptic no-touch wire handling, irrigation of pilot holes to remove debris, no wire or pin drilling through soft-tissue, use of soft-tissue protection sleeves when drilling, proper skin incisions and heat prevention by continuous saline cooling, no use of tourniquet, predrilling, stop-and-start drilling, and pin insertion by hand have all been proposed as techniques to lower the risk of pin site infection.
The aim of this study was to investigate if surgical techniques, of any kind, for insertion of the pins and wires of an external fixator have any effect on pin site infection based on a review of current literature.
This systematic review is reported according to the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. The protocol was registered before startup and published in the international prospective register of systematic reviews with the ID number CRD42021270301.
Eligibility criteria for inclusion of studies in this review were primarily based on components of a PICO framework:
- (P) Population: Patients of all ages (adults and pediatric) in whom application of an external fixator (of any kind) was done either due to trauma or reconstruction
- (I) Intervention: All surgical techniques with proposed preventive measures to lower pin site infection
- (C) Comparator: Any alternative surgical techniques
- (O) Outcome: Rate of pin site infection.
Due to expected scarcity of literature, we included studies in all languages and all study types including clinical trials (randomized controlled trial (RCT), nonrandomized controlled trials (nRCT), and all types of observational studies (cohort [prospective and retrospective], case–control, and case series) on human participants published since 1970. We did not include studies comparing two or more different implants such as wires versus half-pin or different coatings of half-pins.
A systematic literature search was performed in August 25, 2021, searching the following electronic databases; MEDLINE, EMBASE, CINAHL, Google Scholar, and the Cochrane Central Register of Controlled Trials. In addition, the reference lists of relevant studies were screened for additional eligible articles. Searching Google Scholar, we screened the first 1000 records.
The search strategy included the key terms “external fixator” in combination with “pin site infection” or “pin tract infection.” A more specific search strategy was based on a combination of MESH text words based on (P) population and (O) outcome of the PICO framework:
- (P): “External fixator” (MESH term) Or “ilizarov technique” (MESH term) Or “external fix*” Or “circular fix*” Or “ilizarov*”
- (O): “Bone wire” (MESH term) Or “Bone nails” (MESH term) Or “wire*” Or “halfpin*” Or “pin site*” Or “pin tract * And “infections” (MESH term) Or “infect*” Or “sepsi*.”
Search results were extracted to the electronic reference management program Covidence (Veritas Health Innovation, Melbourne, Australia). Duplicates were removed automatically by the program. Two of the authors independently screened the remaining articles and identified relevant publications based on titles and abstracts. The full versions of potentially relevant articles were read by two authors independently to determine eligibility. Disagreements were resolved with discussion among the three authors. Reasons for exclusion of publications were recorded. None of the authors were blinded to the author affiliation of the screened studies.
Data extractions of all included publications were performed independently by the main author and cross-checked for errors by each of the other two authors. Disagreements were resolved with discussion among the three authors.
Data of interest for extraction were type of surgical technique for application of wires or half pins, type of external fixator (trauma or reconstruction), rate of pin site infection, and classification used to diagnose a pin site infection.
Study risk of bias assessment
All three authors independently assessed methodological quality using the modified Downs and Black numerical rating scale checklist. This checklist was chosen as it can be used to assess both randomized as well as nonrandomized studies. Quality was assessed based on study quality, external validity, study bias, confounding/selection bias, and power analysis. The modified scale ranges from 0 to 28 with quality levels graded according to Hooper et al.: poor (0–14)), fair, (15–19), good (20–25), and excellent (26–28).
Due to scarcity of the included studies and the heterogeneity of interventions investigated, it was not possible to perform a meta-analysis on extracted data. Data were presented descriptively as presented by the individual study.
Our search initially resulted in a total of 3295 studies included for screening of which 1102 were duplicates. Following screening by title/abstract and full-text readings, we ended up with a total of two studies eligible for inclusion. Figure 1 shows a flowchart diagram of the search strategy and [Table 1] the characteristics of the included studies.
The two studies included were both using pin site infection as the primary outcome. In both studies, infection at pin site was evaluated using the grading score described by Paley. Both studies only included Grade 2 and 3 as pin site infections, excluding Grade 1 (inflammation).
The study by Catagni et al. investigated the difference between applying a half-pin with threads outside the skin compared to a half-pin with threads inside the skin. The study was designed as a one-time evaluation (cross-sectional design) of pin sites with a mean duration of frame application at time of evaluation of 118 days (range, 27–390). The investigators evaluating the pin sites were not blinded to the technique being used. The half-pins were applied in combination with wires on a circular fixator constructed as a modified Ilizarov frame. The half-pins were not applied with threads in-or outside the skin by a predefined randomization method. At the time of evaluation n = 563 half-pins with threads outside the skin were identified and compared to n = 530 half-pins with threads inside the skin. No statistical difference between the two application methods was found in relation to pin site infection (n = 17 infected half-pins [threads outside] vs. n = 17 infected half-pins [threads inside] [P = 0.429]).
The study by Hutchinson et al. investigated the difference between half-pins inserted by direct-drilling or by predrilling followed by hand-insertion. The study was designed as a prospective cohort study. The half-pins were applied as a four-pin two-bar monolateral external fixator to treat distal radius fractures. Each patient had two half-pins applied by direct drilling and two by predrilling using a standardized alteration method based on the patient's medical record number. N =100 half-pin inserted by direct drilling was compared to n = 100 half-pins inserted by predrilling and hand-insertion. Pin site evaluation was made in the office at some point, not specified by the author, during the 6–8 weeks the frame was applied. The investigators evaluating pin site were blinded to the surgical technique that had been used. A total of n = 16 pins sites were infected affecting 13 patients. No statistical difference between the two techniques were found in relation to pin site infection (n = 8 infected half-pins [direct drilled] vs. n = 8 infected half-pins [predrilled] [P = 0.5]).
The methodological quality of both studies was fair according to the Downs and Black numerical rating scale [Table 2].
This review highlights that publications investigating surgical techniques for handling wires and pins with external fixators to reduce pin site infection is sparse as only two studies have been included. Previous reviews on prevention of pin site infection do however outline that prevention or minimizing the risk of pin site infection starts in the operating theater with proper surgical technique. Most authors advocating for meticulous surgical technique refer to the same study by Davies et al. from 2005. Davies et al. compared in a prospective setting two different protocols for care of pin sites (British consensus protocol vs. Russian Ilizarov protocol). Both protocols included recommendations for several different measures (both surgical techniques of pin/wire handling and for the pin site aftercare). The study did not elaborate on the effect of each single measure on its own but compared the effect of application of the whole protocol. The authors reported a significant reduction in the rate of pin site infection using the Russian Ilizarov protocol. Although not investigating which measures were most effective (the different surgical techniques or the aftercare) to prevent pin site infection the authors stated, “It should be emphasized that any strategy for reducing infections begins in the operating theater.” Although evidence is sparse, this sentence has been adapted and repeated by several authors. In other cases, it seems that expert opinion and experience with an insertion technique without direct correlation to reduction of pin site infection is adapted in several reviews. The effect of most techniques seems questionable as they have not been evaluated in a study but primarily based on an author's preferable approach.
Our review indicates that only two surgical techniques have been investigated in relation to prevention of pin site infections. Both studies are of low quality which must be acknowledged in interpretation the results. However, based on current evidence it seems that there are no clinical differences whether pins are inserted by direct drilling or by predrilling or if the threads of the pins are left in- or outside the skin. The study by Hutchinson et al. did not find any differences in relation to pin site infection, correlating with their clinical impression they would not recommend direct drilling. Reason for not recommending direct drilling was related to their results from a laboratory study finding significantly elevated temperatures at bone level associated with this technique. In this study laboratory results seems to outweigh clinical results. Both studies used a published classification system for pin site evaluation, but only in one study, the assessors were blinded to the surgical technique used. Furthermore, both studies are very heterogeneous when it comes to type of external fixator (monoliteral vs. circular frame), length of application of external fixator at time of evaluation (weeks vs. months), and indications for application of external fixator (upper limb fracture vs. lower limb fracture and fracture treatment vs. limp reconstruction). This makes it very difficult to make a general conclusion as results based on a monolateral wrist fixator used for 6–8 weeks most likely is not applicable to a circular frame used for lower limp reconstruction when used for 8–12 months.
Based on our review of the current literature, we conclude that the effect of most techniques seems questionable as they are not correlated to a positive effect investigated in a study but primarily based on an author's experience or preferable approach. To investigate the real effect of surgical techniques, we advocate for future studies focusing on the effect of a single surgical technique in a multicenter randomized study with a focus to eliminate confounding factors including different medical conditions for frame application (acute vs. reconstructive and upper vs. lower limb), different frame constructs, different application methods, and different postoperative pin site protocols. We would recommend that pins and wires were applied in the same anatomical locations in all patients using the two different techniques to be compared randomized by pin site. The patient would then be case and control eliminating many confounders.
Pin site infection continues to be a very common problem treating patients with external fixators. Due to implants crossing the skin barrier, infections at pin sites are probably unavoidable. Wire and half-pin insertion technique may influence the risk of developing a pin site infection, but at present, there is no convincing evidence to support this assumption.
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Conflicts of interest
There are no conflicts of interest.
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