Biomechanical Analysis of Antibiotic-Treated Tendon Grafts With Digital Image Correlation: A Comparison Between Vancomycin, Gentamycin, and Tobramycin Soaking Techniques

Background: Previous research has shown that tendon graft soaking in vancomycin or tobramycin solution has no negative effects on graft mechanical properties, but there are no studies that have investigated graft mechanical properties after soaking grafts in gentamicin. Additionally, nearly all published biomechanical studies are based on data collected from a mechanical load frame or strain gauge, which does not provide insight on local graft strains compared with 3-dimensional digital image correlation (3D-DIC). Purpose/Hypothesis: The purpose of this study was to use 3D-DIC to investigate the effects of vancomycin, tobramycin, and gentamicin soaking on tendon graft mechanical properties. It was hypothesized that (1) no significant difference in mechanical properties exists between the saline control, vancomycin, tobramycin, and gentamicin groups and (2) local graft strain at the graft failure location will be greater than global strain spanning the entire graft length. Study Design: Controlled laboratory study. Methods: Human tibialis anterior, peroneus longus, and tibialis posterior tendon grafts were prepared and evenly separated into 4 groups: control, vancomycin (5.0 mg/mL), tobramycin (1.0 mg/mL), and gentamicin (0.8 mg/mL). Grafts were soaked in antibiotic solution for 10 minutes, then removed and painted via airbrush with water-based black paint. Uniaxial tension testing was then completed at a strain rate of 10 mm/min. Data collected were used to calculate Young modulus (YM), elasticity limit (EL), ultimate tensile strength (UTS), and failure strain (FS). Results: There were no significant differences in YM (P = .49), EL (P = .62), UTS (P = .98), and FS (P = .14) between control, vancomycin, tobramycin, and gentamicin, respectively. Additionally, local strain at graft failure location was larger than global strain across the length of the graft. Conclusion: Soaking tendon grafts in vancomycin, tobramycin, or gentamicin does not alter the mechanical properties of grafts under uniaxial loading. Clinical Relevance: If vancomycin use is not possible or is contraindicated for certain patients, surgeons can soak grafts in tobramycin or gentamicin to achieve similarly effective infection mitigation without weakening the graft.