The influence of pin material and coatings on the incidence of pin site infection after external fixation

Introduction: External fixation is used for a wide variety of surgical treatments. The transcutaneous pins used in external fixation, however, provide a route for bacterial migration from the external to subcutaneous space, and high rates of pin site infection have been reported. The material of which the pin is composed, or any surface coating that is applied, may significantly influence tissue integration and pin site infection. However, clinical data are scarce. The aim of this systematic review and meta-analysis was to summarize the clinical evidence for the role of pin material, and surface coatings, on the incidence of infection at external fixator pin sites. Materials and Methods: A systematic review was performed following registration with PROSPERO. A search was performed using Medline, Embase, and Cochrane. Inclusion criteria were (1) recorded diagnosis of infection, (2) involved external fixation, (3) any bone, (4) English language, (5) human subjects, (5) pin material known, and (6) all levels of evidence. All stages of the review process were performed by two independent reviewers. A meta-analysis was performed using a random effects model meta-analysis to produce odds ratios. Study bias was assessed using the Cochrane risk of bias tool Rob II. Strength of evidence was based on the American Academy of Orthopaedic Surgeons methodology for defining the strength of recommendation. Results: After exclusion, 8 studies were further analyzed. One study compared stainless steel and titanium with an odds ratio of 1.00 (95% confidence interval [CI]: −0.70–2.70). Three studies compared stainless steel to hydroxyapatite (HA)-coated pins with an odds ratio of 0.25 (95% CI: −0.52–1.02). Two studies analyzed titanium compared to HA-coated pins with an odds ratio of 1.12 (95% CI: −4.25–6.48). Two studies analyzed silver compared to stainless steel with an odds ratio of 0.12 (95% CI: −0.89–1.12). However, the strength of evidence was limited for all studies. Overall, 0 studies had a low risk of bias, 4 studies had an unknown risk of bias, and 4 studies had a high risk of bias. Conclusion: There is currently limited evidence of the effect of different pin material or coatings on the incidence of pin site infection, with the available studies showing contrasting results. Further high-quality and adequately powered studies are required to provide definitive guidance.