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.

Investigation of the biomechanical and histopathological effects of autologous conditioned serum on healing of Achilles tendon.

OBJECTIVE: The aim of this study to evaluate the effects of autologous conditioned serum (ACS) on the healing of transected rat Achilles tendons via the assessment of biomechanical and histological parameters. METHODS: The study was conducted on 45 male Sprague-Dawley rats. Five rats were used as donors for ACS preparation. Animals were randomly assigned to the experimental or control group. In both groups, the Achilles tendon was cut transversally and then sutured. In the placebo control and ACS-treated groups, saline or ACS, respectively, was injected into the repair zone three times after surgery. Ten rats from each group (ACS group, n = 20; control group, n = 20) were euthanized at days 15 and 30 after surgery for histopathological (n = 5) and biomechanical (n = 5) testing. The histopathological findings were interpreted using the Bonar and Movin scales. Tendon remodelling was evaluated via the immunohistochemical staining of collagen type 3. Biomechanical effects were assessed by tensile testing. RESULTS: The Bonar and Movin scale scores were significantly better in the ACS-treated group on both day 15 (p = 0.003 and p = 0.003, respectively) and day 30 (p = 0.005 and p = 0.004, respectively). The immunohistochemical density of collagen type 3 was significantly lower in the ACS-treated group on day 30 (p = 0.018). The type 1/3 collagen ratios of the groups were similar on days 15 and 30, as determined by Sirius Red staining (p = 0.910 and p = 0.133, respectively). In the biomechanical assessment results, the ACS-treated group's maximum load to failure values were significantly higher on day 15 (p = 0.049). CONCLUSION: Injection of ACS had a positive effect on the histopathological healing of rat Achilles tendons on days 15 and 30 and on biomechanical healing on day 15. ACS treatment contributed to lowering the collagen type 3 density by day 30. According to our study, ACS may be favourable for the treatment of human Achilles tendon injuries and tendinopathies.