Pin site infection: an unavoidable complication of external fixation?

External fixators, both circular and monolateral, are effective in the treatment of bone deformities. Either using an acute or gradual correction method, the external fixator will provide stable support to the healing bone while allowing the patient to do some activities of daily living, including early weightbearing, when appropriate.

However, the use of external fixation involves the use of screws (pins) and/or wires placed through the skin and fixed to the bone, creating a potential entry point for microorganisms. Since the treatment with an external fixator lasts from a few weeks to several months, the risk of infection at the pin site is considerably high, to the point of being considered unavoidable by some.

But is it really?

In this article, we will explore the signs of a pin site infection, as well as some management strategies. Finally, we will share some approaches to prevent it and the role of patient education.

Signs and symptoms of pin site infection

Pin site infections start at the level of the skin, and this is where attention should be focused. If identified early, an infection can be easily treated and contained; otherwise it may progress into a more significant problem.

It is important for the patient and their family to recognize the early signs of a pin site infection. The most common signs are the appearance of tenderness and increased redness in the area around a pin site. Sometimes the area will also display increased warmth, swelling, pain or drainage compared to the other pin sites. If the infection progresses, the pin may become loose and the skin around it may require debridement to contain the spread of the microorganisms causing the infection.

In rarer but more serious cases, the pin site infection spreads rapidly and causes systemic symptoms, such as fever, fatigue, nausea, vomiting, and/or rashes. This requires prompt treatment in a hospital setting, unlike milder pin infections, which can be managed in the clinic or at home.

Pin site infection management

Most pin site infections are mild, requiring only increased frequency of local care, with some authors advising the use of silver-releasing dressings to control bacterial growth at the pin site. In moderate infections, the increased frequency of pin site cleaning should be accompanied by a course of oral antibiotics. More severe infections require hospital management and intravenous antibiotics, as well as pin replacement in some cases.

Prevention and the role of the patient

Although many authors claim that it is the infection that ultimately induces a pin to become loose, others argue that it is the opposite: if the pin-bone stability is compromised, the movement of the pin will cause skin irritation, which ultimately leads to the bacterial colonization of the pin site and the arrival of an infection. In any case, the presence of an infection at the pin site may jeopardize the success of the treatment.

Pin site infection prevention starts even before the first cut of a surgery, in the planning stage. Here, the surgeon will decide on the most appropriate external fixator for the patient and carefully plan the bone-pin interfaces to ensure that the final construct will withstand the stresses conveyed during the reconstructive period. During surgery, the main goal is to prevent injury to the bone and surrounding soft tissues, avoiding subsequent bacterial colonization of necrotic tissue.

When the patients go home, it is up to them and their families to keep appropriate pin site care. To help them in their task, healthcare staff should provide clear, easy to follow instructions, preferably in both oral and written forms. Every hospital or clinic has their own set of preferred instructions, as there is still no consensus regarding best practices. Pin site cleaning is recommended, although there is divergence both in the frequency (twice daily, daily, or weekly) and the solution used (normal saline or chlorhexidine solution).

Conclusion

Pin site infection is a common problem with external fixators. It may cause pain and distress to the patient, and endanger the success of the treatment. However, early identification and swift management can minimize the impact of pin site infections.

These infections are not unavoidable. As new surgical techniques emerge and newer pins are developed (such as those with hydroxyapatite coating), their combination with effective pin site care protocols contribute to a steady decrease of infections at the pin site.

References

• Matsubara H et al. International Orthopaedics (SICOT) 2006;30:550–4.
• Fragomen et al. HSS Jrnl 2007;3:13–29.
• Ceroni D et al. J Child Orthop 2016;10:605–12.
• Rozbruch SR et al. Strategies in Trauma and Limb Reconstruction 2016;11:75–85.

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