Effects of low molecular weight heparin and rivaroxaban on rat Achilles tendon healing.

Objectives: This study aims to compare the histopathological and biomechanical effects of low molecular weight heparin (LMWH) and rivaroxaban, which are frequently used in orthopedic surgery for thromboembolic prophylaxis, on rat Achilles tendon healing.

Materials and methods: In the study, 36 adult, male Sprague Dawley rats weighing between 300 g and 400 g were used. Three groups were formed including 12 rats in each. Achilles tendons of all rats were cut and repaired. Nadroparin calcium was administered subcutaneously for 21 days at a dose of 170 IU AXa to the first group (LMWH group). Rivaroxaban was administered daily at a dose of 3 mg/kg for 21 days as gastric lavage to the second group (rivaroxaban group). The third group was identified as the control group and no medication was administered in this group. At the end of three weeks, tendons extracted from the groups were examined histopathologically and biomechanically.

Results: Bonar's and Movin's scores obtained as a result of histopathological examination were statistically significantly higher in the control group (p=0.003 and p=0.004, respectively) (high scores indicate that tendon healing is not sufficient). When type I and type III collagen ratios were examined, type I collagen ratio, which should be found at a higher ratio in mature tendon, was statistically significantly higher in rivaroxaban and LMWH groups compared with the control group (p=0.002). As a result of biomechanical examination, higher mean maximum force values were obtained from the rivaroxaban group compared with the LMWH group (p=0.31). Mean maximum force values obtained from the control group were higher than those obtained from the LMWH group (p=0.03) and the rivaroxaban group (p=0.18).

Conclusion: Histopathological examination revealed that both LMWH and rivaroxaban have positive effects on tendon healing. However, the same positive effects were not detected in biomechanical examination.