Delayed infections after posterior TSRH spinal instrumentation for idiopathic scoliosis - Revisited

Objective. To determine the incidence of delayed infections in idiopathic s coliosis treated with TSRH instrumentation, proper wound management after i nstrumentation removal, and whether the previously identified bacterial tre nd remains consistent. Methods. All patients with idiopathic scoliosis greater than or equal to2 y ears after surgery with posterior TSRH instrumentation were included. Those cases with delayed infections were retrospectively reviewed. Time of prese ntation (infection) from index operation, clinical picture, sedimentation r ate, 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 greater than or equal to2 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 fev er). Sedimentation rate averaged 48 mm/hr. All patients had instrumentation removed. Primary closure (1 stage) was performed in 14 patients, and delay ed primary closure (greater than or equal to2 stages) was performed in nine patients. All wounds healed uneventfully. Cultures at the time of instrume ntation removal grew Propionibacterium acnes in 12 patients, Staphylococcus epidermidis (or Staphylococcus coagulase-negative) in 4, Micrococcus varia ns in 1, and Staphylococcus aureus in 1. Five patients had negative culture s. 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 dela yed infections. Intraoperative seeding followed by subclinical quiescent pe riods appears to be the method by which infection occurs. The increased bul k 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 p arenteral antibiotics (2-5 days) followed by short-term oral antibiotics (7 -14 days) is recommended.