Pulsed Nd:YAG laser therapy accelerates fracture healing in a rat femoral osteotomy model.

Abstract

Aims: This study aimed to evaluate the effects of Nd:YAG laser treatment on fracture healing in a rat model. We hypothesized that laser therapy would accelerate healing by stimulating early neovascularization and osteoblast recruitment.

Methods: A total of 54 male Sprague-Dawley rats received intramedullary Kirschner wire (K-wire) osteosynthesis following femoral osteotomy, and were randomly divided into two groups (n = 27 each): the control group, and the laser group that received daily pulsed Nd:YAG laser for ten days immediately after osteotomy. Fracture sites were assessed using micro-CT (μCT; n = 8 at each timepoint), histology (n = 4), and three-point bending tests (n = 4) at week 2, week 4, and week 6, respectively. At week 2, an additional three rats per group were selected for the western blot tests.

Results: Compared to controls, the laser group showed higher vascular endothelial growth factor (VEGF), CD31, and Runx2 protein expression, and significantly higher neovascular area density and osteoblast density (p = 0.025 and p = 0.008, respectively) at week 2. At week 4, the laser treatment led to higher histological fracture healing scale and flexural modulus, and less strain (p = 0.001, p = 0.020, and p = 0.004, respectively). Macroscopically, the laser group showed higher mature bone volume fraction and radiological union score at weeks 4 and 6 (volume fraction: p = 0.017 and p = 0.001; union score: p = 0.001 and p = 0.024, respectively).

Conclusion: Pulsed Nd:YAG laser therapy accelerates multiple quantitative indicators of fracture healing within six weeks in a rat femoral osteotomy model, which was associated with enhanced angiogenesis and osteogenesis during the early healing phase.