Infected nonunion: diagnostic and therapeutic work-up

Abstract

Septic nonunion is one of the major complications in fracture healing. The challenge is to identify the infection as the cause of nonunion first and then to achieve healing of the infection and the bone. Because of the more heterogeneous appearance of an infected nonunion, the prevalence of germ detection in surgical nonunion revision is often underestimated. In aretrospective study between 2010 and 2017, 86patients with radiologically confirmed femoral shaft nonunion without clinical evidence and unremarkable medical history of aflorid infection as the cause of nonunion, who had undergone primary single-stage surgical nonunion revision were analyzed. At least four intraoperatively obtained samples were evaluated for microbiological diagnosis. Adistinction was made between tissue samples with subsequent 48‑h short-term incubation and tissue samples with 14-day long-term cultivation. The finding "germ detection" was made if at least two of the samples demonstrated bacterial growth. In18 of 86patients with a nonunion preoperatively judged to be aseptic, positive bacterial evidence was obtained after short-term incubation. After long-term cultivation, positive bacterial detection was possible in38 of 86patients with a femoral shaft nonunion initially classified as aseptic. Regarding potential risk factors, the two groups demonstrated no relevant differences. In 29patients, 1 pathogen was isolated from the obtained samples, whereas in the remaining 9patients, amixed culture with an average of 2.9 ± 0.5 different bacteria was detected. Identification revealed mainly low-virulence bacteria, most commonly Staphylococcus epidermidis. If the preoperative diagnostics including clinical, laboratory and radiological examination as well as acareful anamnesis reveal indications of apossible infectious event, the surgical nonunion revision should be performed in two stages with specimen collection before definitive nonunion revision. For microbiological diagnosis, several representative tissue samples should independently be obtained from the nonunion site and incubated for 14days. Only in the absence of evidence of septic nonunion is asingle-stage procedure suggested.