The mechanical properties of the human patellar tendon are correlated to its mass density and are independent of sex

Background. A diverse range of values for the mechanical properties of the human patellar tendon has been reported in the literature. Donor age has been excluded as a factor that causes this disparity. However, the effects of donor sex and tissue mass density on the mechanical properties of the patellar tendon have not been established. More importantly, predictors of the mechanical properties of the patellar tendon, used as grafts in anterior cruciate ligament reconstruction surgeries, are not available. Methods. Uniaxial tension tests were performed to determine the effects of donor sex and mass density of the tissue on the mechanical properties of twenty unpaired human patellar tendons (10 male and 10 female; age, 17–50). Mass density of the patellar tendon was determined by measuring its volume and mass. Findings. No evidence of sex-based differences in any of the mechanical properties of the patellar tendon was found. The results revealed a diverse range of mass densities extending from a low of 0.76 g/cm3 to a high of 2.68 g/cm3 (250% difference). Furthermore, it was determined that the ultimate tensile strength (mean = 58.71 MPa), elastic modulus (mean = 507.38 MPa) and strain energy density (mean = 4.59 MPa) of the patellar tendon were significantly correlated to its mass density. The tensile strength and elastic modulus were significantly higher for those patellar tendons having a mass density greater than 1.67 g/cm3. Interpretation. The mass density of the patellar tendon may be considered as an indicator of mechanical properties of the patellar tendon or graft quality.