Background <p>Delayed fracture healing (DFH) is a common and difficult-to-treat complication after fracture surgery. Early diagnosis serves a key function in clinical management. This research seeks to clarify the molecular mechanism underlying how miR-455-5p modulates osteogenic differentiation via QKI(Quaking), thereby laying a foundation for the early detection and targeted intervention of DFH.</p> Method <p>208 femoral neck fracture patients were divided into NFH (normal fracture healing group, <i>n</i> = 115) and DFH (<i>n</i> = 93) groups. The serum level of miR-455-5p and QKI was measured using qRT-PCR(quantitative reverse transcription-polymerase chain reaction). Pearson correlation analysis was performed to assess the correlation. ROC and logistic regression analyses were performed. In vitro experiments with MC3T3-E1 cells explored its role and target via transfection and dual-luciferase assay.</p> Results <p>Serum miR-455-5p was downregulated in DFH (<i>P</i> &lt; 0.01), with diagnostic AUC 0.747, and was an independent risk factor. It increased time-dependently during osteogenic induction. Its inhibition reduced osteogenic markers and suppressed proliferation. QKI has been identified as a target gene of miR-455-5p and exhibits a negative correlation with its expression. The synergistic effect between QKI and miR-455-5p contributes to improved diagnostic performance.</p> Conclusions <p>miR-455-5p promotes osteogenesis by targeting QKI and shows potential as a biomarker and therapeutic target for DFH.</p>