Importance of intraoperative histology in the diagnosis of infection in long bone nonunions - an experimental prospective study

Introduction Diagnosis of infection during revision surgeries for nonunion of long bone fractures is challenging and remains a clinical issue. Paraffin histology is recognized as a confirmatory criterion for fracture-related infection (FRI); however, its results are not available during surgery. Cryohistology (frozen section) offers rapid intraoperative evaluation, but its diagnostic accuracy has not yet been fully validated. The aim of this study was to assess the incidence of infection in patients undergoing surgery for fracture nonunion and to compare the diagnostic yield of cryohistology with the conventional paraffin method. Method In the prospective study, two specimens of soft tissues that surrounded the nonunion were collected intraoperatively from patients. The two specimens were processed by both cryohistology and paraffin embedding methods and analysed for the presence of polymorphonuclear neutrophils (PMNs) per high power field (HPF) of view. The obtained data were analysed using descriptive and non-parametric statistics. Results The study included 36 patients with nonunion of the long bones. Infection was microbiologically confirmed in 16 cases (44%). Cryohistology and paraffin histology detected infection with the same level of sensitivity (18.8%) and specificity (95.0%). Most samples showed no presence of neutrophils; positive findings were recorded in only four patients. Statistical analysis did not show a significant difference between the methods (p > 0.05), suggesting comparable diagnostic yield. Conclusion Cryohistology provides comparable results to paraffin histology while allowing for rapid intraoperative diagnosis. However, due to its low sensitivity, it cannot be used as a standalone diagnostic tool for detecting fracture-related infections. Therefore, histological findings must always be interpreted in conjunction with clinical findings, microbiological results, and other laboratory indicators. Its use may be beneficial as a supplementary method within a multimodal diagnostic approach. However, further validation in larger and more homogeneous patient groups is necessary for its broader implementation in clinical practice.