Aims: The present study investigated Runt-related transcription factor 2 (RUNX2) and collagen type A1 (COL1A1) gene expressions in pseudarthrosis with the objective of creating a novel shaft femoral pseudarthrosis rabbit model.

Methods: Sixteen rabbits were used in this experimental study. We divided rabbits into two groups, control group and pseudarthrosis group. The study aimed to compare bone consolidation between two groups: a control group, where a resection site was created and stabilized using an external fixator on both sides, and the pseudarthrosis (PS) group, where a muscle interposition was performed at the resection site in addition to the external fixation. At eight weeks, radiographic and molecular studies were undertaken to investigate bone consolidation in the resection area. We used Quantitative Polymerase Chain Reaction (Q-PCR) to evaluate the expression of the RUNX2 and COL 1A1 genes.

Results: In the control group, complete bone consolidation was achieved in all rabbits, as evidenced by macroscopic and radiographic assessments showing cortical continuity, a homogeneous medullary cavity, and the formation of a mature, continuous callus with clear cortico-medullary differentiation. In contrast, all animals in the PS group exhibited failed bone healing, characterized by the absence of cortical bridging and the presence of a persistent inter-fragmentary gap, medullary canal obliteration, and resorption of bone ends. At the molecular level, quantitative PCR analysis revealed significantly higher expression of RUNX2 and COL1A1 in the control group compared to the PS group (p = 0.01), with both genes demonstrating a 10-fold upregulation, reflecting increased osteogenic activity associated with successful bone regeneration.

Conclusion: We successfully established a rabbit model of femoral shaft pseudarthrosis, confirmed through the analysis of COL1A1 and RUNX2 gene expression levels.

Pseudarthrosis, RUNX2, COL1A1, Rabbits