Effect of tenoxicam on fracture healing in rat tibiae.

Background: Nonsteroidal anti-inflammatory drugs have been implicated in the development of delayed unions and nonunion after fractures in animal models. Previous investigations have identified two important factors as determinants of delayed fracture healing: early drug administration and a dose-dependent effect.

Objective: The purpose of this investigation was to study the effect of tenoxicam, a nonsteroidal anti-inflammatory drug, on the fracture healing process in rat tibiae.

Methods: Fifty-eight Wistar rats were randomly divided in four groups (I, II, III, and IV). Group I (control group, n=12) was given 0.1ml saline solution per day intramuscularly. Groups II (n=12), III (n=12), and IV (n=12) were administered 10mg per kg per day of tenoxicam intramuscularly. Administration of substances was begun on a week before to 48h after the fracturing procedure and continued during the entire experiment. Callus formation was studied histologically and histomorphologically, using light microscopy. In addition, a histologic grading based on the morphologic stage of fracture healing was carried out at 4 weeks, according to the criteria proposed by Allen et al.

Results: There was a significant difference in treatment effect between Group I (saline solution) and Groups II, III, and IV (tenoxicam) (P=0.07). Histologically and histomorphologically, there were qualitative and quantitative delay in callus formation at all tenoxicam groups. This was more pronounced the earlier the nonsteroidal anti-inflammatory drug was started, although no significant difference could be detected between Groups II, III, and IV (P>(alpha=10%)). Four weeks after fracture, Group I (n=3) showed complete osseous union, Groups II (n=3) and III (n=3), complete cartilaginous union, and Group IV (n=3), incomplete osseous union, according to Allen et al. By using this rating scale, the difference between control and drug-treated groups was statistically significant (P<0.1).

Conclusion: Under studied conditions, this investigation shows that administration of tenoxicam intramuscularly delays fracture healing process in rat tibiae. These results suggest the hypothesis that early drug administration may delay bone healing after experimental fractures in animals, although it could not be detected statistically significant.