Delayed Infections After Posterior TSRH Spinal Instrumentation for Idiopathic Scoliosis

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Abstract
Objective. To determine the incidence of delayed infections in idiopathic scoliosis treated with TSRH instrumentation, proper wound management after instrumentation removal, and whether the previously identified bacterial trend remains consistent. Methods. All patients with idiopathic scoliosis ≥2 years after surgery with posterior TSRH instrumentation were included. Those cases with delayed infections were retrospectively reviewed. Time of presentation (infection) from index operation, clinical picture, sedimentation rate, presence of pseudarthrosis, organisms grown on culture, type of wound closure, and duration of antibiotics were examined. Results. A total of 489 patients were identified ≥2 years postoperation; 23 had delayed infections (4.7%). Time of presentation averaged 27 months after initial surgery. Spontaneous drainage occurred in 15 patients, fluctuance in 6, and neither in the remaining 2 (pain and fever). Sedimentation rate averaged 48 mm/hr. All patients had instrumentation removed. Primary closure (1 stage) was performed in 14 patients, and delayed primary closure (≥2 stages) was performed in nine patients. All wounds healed uneventfully. Cultures at the time of instrumentation removal grew Propionibacterium acnes in 12 patients, Staphylococcus epidermidis (or Staphylococcus coagulase-negative) in 4, Micrococcus varians in 1, and Staphylococcus aureus in 1. Five patients had negative cultures. After removal, patients received parenteral antibiotics; in 21 of these patients this was followed by oral antibiotics. Conclusions. Low-virulent skin organisms are primarily responsible for delayed infections. Intraoperative seeding followed by subclinical quiescent periods appears to be the method by which infection occurs. The increased bulk and modularity of modern instrumentation systems can lead to inflammation and bursa formation, thus contributing significantly to the activation of these infections. Primary wound closure results in successful wound healing. Delayed closure after 48 hours is unnecessary. Short-term postoperative parenteral antibiotics (2–5 days) followed by short-term oral antibiotics (7–14 days) is recommended.