Delayed methicillin-resistant Staphylococcus aureus-induced osteomyelitis of the tibia after pin tract infection: two case reports
© The Author(s). 2017
Received: 21 July 2016
Accepted: 26 December 2016
Published: 31 January 2017
Pin tract infection is a common complication of external fixation. It usually heals after treatment with debridement, antibiotics, and/or pin removal, only rarely developing into delayed osteomyelitis. We treated two patients with delayed methicillin-resistant Staphylococcus aureus-induced osteomyelitis of the tibia following pin tract infection.
One patient, a diabetic 60-year-old Japanese man, underwent definitive external fixation using an Ilizarov fixator for postoperative osteomyelitis of an open fracture of his left ankle. One year after removing the external fixator, he developed methicillin-resistant Staphylococcus aureus-induced osteomyelitis of the tibial pin site. He underwent surgical debridement four times. No recurrence was seen 2 years 8 months after the last debridement. Another patient, a healthy 38-year-old Japanese man, underwent bilateral temporary external fixation for a right ankle open fracture and a comminuted fracture of the left tibial plateau. Three months after removal of the external fixator, he was diagnosed with methicillin-resistant Staphylococcus aureus-induced osteomyelitis of the bilateral tibial pin sites. He underwent surgical debridement three times, but the infection of his right tibia persisted. Finally, a gastrocnemius muscle flap was placed. No recurrence was seen 2 years after this last surgery.
Pin tract infection should not be considered a minor complication because osteomyelitis may develop, requiring treatment that is more aggressive than curettage of the pin tract. A gastrocnemius flap is a useful treatment option for refractory osteomyelitis because flap harvest causes less functional disturbance and is a relatively easy surgical technique.
KeywordsCase report External fixation Methicillin-resistant Staphylococcus aureus Osteomyelitis Pin tract infection
Temporary external fixation is applied for a limited time to treat open fractures and periarticular fractures associated with severe soft tissue damage. It is also recommended for damage control orthopedics in patients with multiple injuries . Definitive ring fixation is applied for longer periods to address infected nonunion or large bone defects . Pin tract infection (PTI) is a common complication associated with both temporary and definitive external fixation . It usually heals after treatment with debridement, antibiotics, and/or pin removal, only rarely developing into delayed osteomyelitis. Surgical wounds are most at risk of methicillin-resistant Staphylococcus aureus (MRSA) infection. MRSA infections are worse than those caused by other pathogens because of the limited choice of available efficacious antibiotics, thus making it difficult to eradicate these strains. The MRSA isolation rate in healthcare settings is higher in Japan than in other countries [4, 5]. We report the treatment of two rare cases of delayed MRSA-induced osteomyelitis of the tibia after PTI.
Although the incidence of PTI has been reported to range from 3 % to more than 80 % , it rarely evolves into a major infection. It is classified according to the Checketts–Otterburn classification . Grades 1 to 3, classified as minor infections, are the most frequent and usually heal following debridement, antibiotics, and/or pin removal. In contrast, the two cases reported here were classified as grade 6 (major infections), which are relatively rare. That is, the pin tract healed initially after fixator removal but became infected, producing a pus discharge months later. We currently use temporary external fixators for treating the 20 to 30 lower limb fractures that we encounter per year. The incidence of major infections, such as osteomyelitis, has been no more than 1 % during the past 5 years in our institution (unpublished data).
PTI should not be considered a minor complication because once osteomyelitis has developed its treatment entails measures that are more aggressive than curettage of the pin tract. Nevertheless, PTI is a common complication of external fixation. Kazmers et al.  pointed out that there is no consensus regarding the optimal measures for preventing PTI. In addition, there is a paucity of randomized controlled trials and meta-analyses, as well as a lack of control groups in many studies. Although studies have evaluated a number of variables (that is, cleansing solutions, dressing types, frequency of cleaning), it has been difficult to isolate the effect of any one variable in the event of a positive result.
Parameswaran et al.  reported a 3.9 % incidence of PTI associated with the use of ring fixators, which differs significantly from the 12.9 % incidence associated with the use of unilateral fixators. This discrepancy suggests that the rate of PTI associated with the use of wires is lower than that for PTI associated with the use of half-pins. In addition, extra attention is needed for patients with poorly controlled glycemia, such as in the patient described in our Case 1. This is true even when using fine wires because definitive ring fixators are usually applied for long periods and diabetes is a risk factor for PTI . Several researchers have promoted the use of pin materials to prevent PTI. Qu et al.  reported that there were no signs of infection around percutaneous pins coated with a micron-thin sol–gel/triclosan film in distal rabbit tibias. Shirai et al.  developed techniques to coat titanium implant surfaces with iodine. They concluded that iodine-supported titanium pins could decrease the PTI rate and had no impact on thyroid function. It is expected that these techniques and materials will be applied to patients in the future.
Bibbo and Brueggeman  reported that care should be taken to ensure that, during pin insertion, proper pin cooling and, in the case of half-pins, predrilling should be performed to prevent thermal osteonecrosis and skin irritation. Ktistakis et al.  noted that meticulous surgical technique is essential for preventing infection. For example, they recommended the use of a well-positioned skin incision, a non-touch technique for wire handling, advancement of the pin into the soft tissue by tapping rather than drilling, predrilling, and washing out bone debris before inserting half-pins. Prevention of thermal osteonecrosis is considered a target for improvement in our institution because we do not perform cooling during pin insertion by drilling.
It is recommended that the pin site be treated daily by cleansing the pin–skin interface with simple isopropyl alcohol, freshening the wound edges with sharp dissection, and closing the wound primarily with standard closure techniques after removing the pins . Several reports recommend chlorhexidine as a cleansing agent for pin sites. Cam et al.  compared a 10 % povidone–iodine solution and chlorhexidine 2 mg/ml and reported that PTI was observed in 27.9 % of the povidone–iodine group and in 9.2 % of the chlorhexidine group. W-Dahl and Toksvig-Larsen  compared a chlorhexidine 2 mg/ml solution and sodium chloride 9 mg/ml solution and reported that PTI was found in 9 % of the chlorhexidine group and in 17 % of the sodium chloride group. Polyhexamethylene biguanide or 1 % silver sulfadiazine-impregnated gauze dressing of the pin site has been recommended to prevent PTI [14, 15]. We routinely use once-daily pin site care with chlorhexidine 2 mg/ml solution, but we need to search further to determine whether it is the most appropriate method.
In case 2, primary wound closure was performed successfully using a gastrocnemius muscle flap and skin grafting. The abundant blood flow provided by the muscle flap is an advantage because it delivers antibiotics into the medullary cavity to help control the infection . The patient reported no complaints related to gait or activities of daily living other than mild weakness during ankle planter flexion. The gastrocnemius muscle flap is a useful treatment option for refractory osteomyelitis because the flap harvest causes less functional disturbance and is a relatively easy surgical technique.
We report two cases of MRSA-induced osteomyelitis of the tibia after PTI. Delayed osteomyelitis with MRSA is uncommon as it is a highly virulent bacteria and leads to early infection. PTI should not be considered a minor complication because once osteomyelitis has developed more aggressive treatment is required as simple curettage is likely to fail. Local pin care is important to prevent infection. Furthermore, we suggest that avoiding thermal osteonecrosis during pin insertion and controlling systemic comorbidities such as diabetes are also important for preventing PTI. The gastrocnemius flap is a useful treatment option for refractory osteomyelitis because flap harvest causes less functional disturbance and is a relatively easy surgical technique.
Methicillin-resistant Staphylococcus aureus
Pin tract infection
We thank the reviewers for their valuable comments and suggestions.
Availability of data and materials
Data sharing is not applicable to this article as no data sets were generated or analyzed during the current study.
KH, YU, and YK performed the operation. KH and YK collected the data and drafted the manuscript. YU and MW revised the manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent was obtained from the patients for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
Ethics approval and consent to participate
This study was approved by the Institutional Review Board for Clinical Research of Tokai University School of Medicine. All patients received information regarding the purpose, and informed consent was obtained from all patients.
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