OBJECTIVES: The aim of this study was to examine the effect of N-acetylcysteine (NAC), which has antioxidant properties, on healing in a rat femoral diaphysis fracture model. MATERIALS AND METHODS: Twenty-four male Wistar-Hannover rats were randomly divided into two groups: experimental (n=12) and control groups (n=12). An open femur fracture model (osteotomy) was applied to the right femora of both groups. Fixation was performed with Kirschner wire. While intraperitoneal NAC treatment was given to the experimental group for 21 days after surgery, an equal volume of intraperitoneal saline injection was administered to the control group. At the end of this period, the femurs obtained from the sacrificed animals were examined histopathologically, radiologically, and biomechanically. Huo scoring was used for histopathological examination. The samples were examined radiologically according to the Radiographic Union Scale in Tibial Fractures (RUST) scoring system. The three-point bending test was used for the biomechanical examination. RESULTS: According to the third-week results, NAC could histopathologically contribute positively to fracture healing in rats (p=0.003 and p<
0.05, respectively). Considering radiological and biomechanical parameters, no significant difference was observed between the groups in terms of healing (p>
0.05). However, a positive significant correlation (67.7%) was found between histopathological results and radiological findings (p=0.016 and p<
0.05, respectively). CONCLUSION: Our study results indicate that NAC may have a histopathologically positive effect on the healing process in rat traumatic fractures. Based on these findings, NAC preparations may be used as a supportive agent in the treatment of fractures. Further clinical studies are needed.