Comparative effects of thiocolchicoside and etodolac on fracture healing in a rat femur model

Fracture healing may be influenced by pharmacological agents commonly prescribed for pain control and muscle spasm; while the effects of non-steroidal anti-inflammatory drugs (NSAIDs) on bone healing have been widely discussed, data regarding centrally acting muscle relaxants such as thiocolchicoside remain limited. This study aimed to evaluate the effects of thiocolchicoside and etodolac, administered alone and in combination, on fracture healing in a rat femur fracture model. Seventy-two male Wistar albino rats were randomly assigned to four groups (n = 18): thiocolchicoside, etodolac, thiocolchicoside + etodolac, and control. A standardized mid-diaphyseal femoral osteotomy was performed and stabilized with intramedullary fixation. Treatments were administered orally for 15 days. Animals were sacrificed on postoperative days 15, 30, and 45. Fracture healing was assessed using radiological, histopathological, and biomechanical methods. Radiological healing scores differed significantly among groups at all time points (p < 0.05), with the control group showing consistently higher Lane–Sandhu scores than the etodolac and combined thiocolchicoside + etodolac groups, particularly at postoperative days 15 and 30. Histopathological evaluation revealed significant intergroup differences on postoperative days 15 and 30 (p < 0.001) and day 45 (p = 0.002), with the lowest Huo scores observed in the combined treatment group and the highest scores in controls. Biomechanical testing showed significant differences in maximum load to failure among groups at all evaluated time points (p < 0.01), where femurs from the etodolac and combined treatment groups exhibited lower mechanical strength compared with controls. Within-group analyses demonstrated significant improvements in histopathological and biomechanical parameters over time in all groups (p < 0.001). Thiocolchicoside and etodolac were associated with reduced radiological, histopathological, and biomechanical fracture healing parameters compared with untreated controls, particularly during the early healing phase. The combined thiocolchicoside + etodolac regimen demonstrated the most pronounced delay in healing metrics. Although causality cannot be established, these results indicate that commonly used analgesic and muscle-relaxant agents may transiently modulate early fracture repair and warrant further experimental and clinical investigation.