Mechanical Analysis of Extra-Articular Knee Ligaments. Part two: Tendon grafts used for knee ligament reconstruction

Objectives: The aim of this study was to provide information about the mechanical properties of grafts used for knee ligament reconstructions and to compare those results with the mechanical properties of native knee ligaments. Methods: Eleven cadaveric knees were dissected for the semitendinosus, gracilis, iliotibial band (ITB), quadriceps and patellar tendon. Uniaxial testing to failure was performed using a standardized method and mechanical properties (elastic modulus, ultimate stress, ultimate strain, strain energy density) were determined. Results: The elastic modulus of the gracilis tendon (1458 +/- 476 MPa) (P < 0.001) and the semitendinosus tendon (1036 +/- 312 MPa) (P < 0.05) was significantly higher than the ITB (610 +/- 171 MPa), quadriceps tendon (568 +/- 194 MPa), and patellar tendon (417 +/- 107 MPa). In addition, the ultimate stress of the hamstring tendons (gracilis 155.0 +/- 30.7 MPa and semitendinosus 120.1 +/- 30.0 MPa) was significantly higher (P < 0.001, respectively P < 0.05), relative to the ITB (75.0 11.8 MPa), quadriceps tendon (81.0 +/- 27.6 MPa), and patellar tendon (762 +/- 25.1 MPa). A significant difference (P < 0.05) could be noticed between the ultimate strain of the patellar tendon (24.6 +/- 5 .9%) and the hamstrings (gracilis 14.5 +/- 3.1% and semitendinosus 17.0 +/- 4.0%). No significant difference in strain energy density between the grafts was observed. Conclusions: Material properties of common grafts used for knee ligament reconstructions often differ significantly from the original knee ligament which the graft is supposed to emulate. (C) 2017 Elsevier B.V. All rights reserved.