Mechanical Properties of Tibialis Tendon Grafts Are Unchanged by Soaking in Tobramycin.

Abstract

Background: Tendon graft soaking in vancomycin solution minimizes surgical infection risk and has no effect on graft strength, but the intermittent vancomycin shortages, presence of vancomycin-resistant organisms, and treatment needs of patients with vancomycin hypersensitivity merit investigation of alternative antibiotics. Tobramycin prevents infection at low concentrations and is a cost-effective alternative, but it is unknown if tobramycin alters graft mechanical properties.

Purpose/hypothesis: The purpose of this study was to investigate the effects of tobramycin soaking on tendon graft mechanical properties. It was hypothesized that tobramycin soaking will not affect tendon graft mechanical properties.

Study design: Controlled laboratory study.

Methods: A total of 30 tibialis tendon grafts were wrapped in saturated gauze swabs containing saline (control; n = 10), vancomycin (n = 10; 5 mg/mL), or tobramycin (n = 10; 1 mg/mL) for 10 minutes. Grafts were then removed from the treated gauze swab wraps and mechanically tested under uniaxial tension loading conditions. Grafts were pulled at a rate of 10 mm/min to failure. Force and displacement data from each test were used to calculate the Young modulus (MPa), ultimate tensile stress (MPa), and elasticity limit (MPa).

Results: There were no significant differences in Young modulus (552 ± 108, 583 ± 98, and 660 ± 237 MPa; P = .62), ultimate tensile stress (91.5 ± 20.8, 96.6 ± 17.8, and 99.7 ± 33.3 MPa; P = .85), or elasticity limit (51.7 ± 16.4, 53.2 ± 13.8, and 52.3 ± 15.3 MPa; P = .98) between the control, vancomycin, and tobramycin groups, respectively.

Conclusion: Soaking of tibialis tendon grafts with tobramycin does not appear to alter mechanical properties of the tendon graft under uniaxial load conditions.

Clinical relevance: If vancomycin use is not possible or contraindicated for certain patients, surgeons can soak grafts in tobramycin to achieve similarly effective infection mitigation without weakening the graft.