Soaking in Povidone-Iodine, Chlorhexidine, Teicoplanin, Vancomycin, and Saline Differentially Alters Porcine Flexor Tendon Size and Biomechanical Properties

To compare the impact of povidone-iodine, chlorhexidine, vancomycin, and teicoplanin on the size and biomechanical properties of porcine flexor tendon grafts. Porcine deep digital flexor tendons (N = 120) were collected in pairs and allocated into povidone-iodine, chlorhexidine, vancomycin, teicoplanin, and saline solution groups (12 pairs per solution). The tendons from one side underwent a 30-minute soaking in these solutions, whereas those from the other side were wrapped in saline solution-soaked gauze. Tendon cross-sectional area (CSA) was measured before and after soaking, along with unsoaked controls. Tensile testing to failure was performed. Stiffness, load at failure, modulus, and stress at failure were calculated. Soaking in povidone-iodine and chlorhexidine decreased the average CSA by 8% (-0.9 mm2 [95% confidence interval (CI), -1.7 to -0.2 mm2], P = .02) and 13% (-1.1 mm2 [95% CI, -1.5 to -0.7 mm2], P < .001), respectively. Conversely, the average CSA increased by 12% after soaking in teicoplanin (1.0 mm2 [95% CI, 0.7 to 1.3 mm2], P < .001) and by 6% after soaking in vancomycin (0.7 mm2 [95% CI, 0.2 to 1.2 mm2], P = .01), similar to saline solution (11% increase; 0.8 mm2 [95% CI, 0.4 to 1.1 mm2], P < .001). The stiffness of tendons soaked in chlorhexidine was 8% lower than that of unsoaked contralateral controls (-13.3 N/mm [95% CI, -31.0 to -6.9 N/mm], P = .01), but stress at failure increased by 15% (8.9 MPa [95% CI, 0.6 to 17.2 MPa], P = .04). We observed no significant difference in tensile properties due to soaking in other solutions. Soaking porcine flexor tendons in povidone-iodine and chlorhexidine resulted in a decrease in CSA, whereas soaking in vancomycin and teicoplanin led to an increase, similar to saline solution. No significant side-to-side differences in average CSA were observed. Soaking in chlorhexidine decreased stiffness but increased stress at failure. None of the solutions affected load at failure. It is important to understand the impact of soaking porcine flexor tendon grafts in various antimicrobial solutions to ensure that there are no harmful biomechanical effects to the tissues used in the clinical setting.