Histopathological and histomorphometric investigation of the effects of different irrigation solutions on Achilles tendon healing in rats.

Objectives: This study aimed to examine the effect of irrigation fluids containing povidone-iodine (PVP-I), rifampicin (RF), and chlorhexidine gluconate (CHG) used during surgery on healing on a rat Achilles tendon model.

Materials and methods: Twenty-eight male Sprague-Dawley rats (range, 300 to 400 g) were used in the experiment carried out between November 2022 and December 2022. The rats were divided into PVP-I, RF, CHG, and control groups, with seven rats in each group. Following the tenotomy and repair of the right Achilles tendon, the surgical site was irrigated using PVP-I, RF, CHG, or normal saline (the control group) for 2 min. All rats were sacrificed on the 21^st postoperative day. The samples were evaluated histomorphometrically using the scoring system modified by Svensson, Soslowsky, and Cook and histopathologically using the Bonar and Movin classifications.

Results: The RF group gave better results in all three scoring systems compared to the control, PVP-I, and CHG groups (p=0.008, p=0.002, and p=0.006, respectively). Cellularity, rounding, and tenocyte morphology showed a significant difference in favor of the RF group (p=0.004). While the distribution of ground substance glycosaminoglycans showed a significant difference in favor of the RF group, there was no significant difference among the other groups (p=0.22).

Conclusion: Irrigation solutions containing PVP-I, RF, or CHG show no negative effect on Achilles tendon healing. Moreover, the findings suggest that RF irrigation can accelerate the healing process.