gms | German Medical Science

Objectives: Fracture nonunion remains a relevant complication after osteosynthesis and infection is the underlying cause in up to 40% of cases. Infected nonunion needs specific intra- and postoperative treatment in revision surgery but is challenging to diagnose. Especially in the case of low grade infection with no clinical or radiological signs for infection clinicians are seeking for additional preoperative diagnostic tools such as blood tests but standard blood marker did not serve as a sufficient tool for proper diagnosis. Different micro RNA profiles influence bone healing and were used to identify infected nonunion in tissue samples. The aim of our study was to assess miRNA exosomes profiles in blood samples from infected and aseptic tibial nonunion patients by next generation sequencing technique to identify differently expressed miRNA that might ideally serve as a biomarker to diagnose infected nonunion preoperatively.

Methods: This prospective study enrolled adult patients in eight German level 1 trauma centers who underwent revision surgery of tibia nonunion after fracture fixation. Patients with immunosuppressive or anti-infective therapy, cancer or immune disease, nicotine abuses and diabetics were excluded. Nonunion patients were grouped into infected or aseptic nonunion after assessing bacterial infection and tissue morphology of retrieved samples. Diagnosis of infection followed the fracture related infection consensus group criteria with additional consideration of patient’s healing course within one year after revision surgery.

From preoperative plasma sample exosomes were isolated (exoRNeasy Midi (QIAGEN)) and miRNA was sequenced (NextSeq (Illumina Inc.)) by Qiagen. Differential expression analysis was performed with ‘Empirical analysis of DGE’ - algorithm of the CLC Genomics Workbench 21.0.4 by Qiagen. Significant changes were defined as False discovery rate <0.01.

Results and conclusion: We recruited ten aseptic and eleven infected nonunion patients. All patients were male and matched for confounding factors like age, open fracture or AO fracture typ. Subgroup comparison revealed has-miR-4516 to be higher expressed in infected than aseptic nonunion of initial type A fracture patients. In initial type B fracture nonunion hsa-miR-4516, has-miR-16-5p and has-miR-486-5p were downregulated in infected nonunion whereas has-miR-206 was upregulated in this subgroup.

Our detected findings do not match with already reported findings in literature. However, to our knowledge there was no comparison of miRNA exosomes from plasma samples in infected vs aseptic nonunion yet. We therefore plan to validate our detected differences in miRNA expression in an already recruited patient collective and correlate these findings with reported data from tissue and animal studies.