Effect of cyclic preconditioning on the tensile properties of human quadriceps tendons and patellar ligaments

Abstract

Preconditioning of soft tissues has become a common procedure in tensile testing to assess the history dependence of these viscoelastic materials. To our knowledge, this is the first study comparing tensile properties of soft tissues-before and after cyclic preconditioning with high loads. Sixteen quadriceps tendon-bone (QT-B) complexes and 16 patellar ligament-bone (PL-B) complexes from a young population (mean age 24.9 +/- 4.4 years) were loaded to failure with a deformation rate of 1 mm/s. Half of the QT-B and the PL-B complexes underwent 200 uniaxial preconditioning cycles from 75 to 800 N at 0.5 Hz before ultimate failure loading. High-load preconditioning was made possible by the development of a highly reliable and easy-to-use cryofixation device to attach the free tendon end. PL-B complexes were more influenced by preconditioning than the QT-B complexes. Ultimate failure load, stiffness at 200 N and stiffness at 800 N were significantly higher for PL-B complexes after preconditioning, while the structural properties of QT-B complexes exhibited no significant alterations. The values of the mechanical properties like Young's modulus at 200 N and 800 N were much higher for both preconditioned specimen groups. In addition, ultimate stress was augmented by preconditioning for PL-B complexes. Hysteresis and creep effects were highest during the first few loading cycles. More than 160 cycles were needed to reach a steady state. Beyond 160 cycles there was no further creep, and hysteresis was almost constant. Creep values were 2.2% of the initial testing length for the QT-B and 3.2% of the initial testing length for the PL-B complexes. The effect of cyclic preconditioning seems to be caused by progressive fiber recruitment and by alterations of the interstitial fluid milieu.

Collagen network strengthening following cyclic tensile loading

“…The application of cyclic loading may also alter the failure properties of tissue. Remarkably, an increase in the ultimate stress was observed after cyclic loading in tendons [17,18,21], ligaments [17,18] and collagen gels [22]. A study by Legerlotz et al [23], however, showed a decrease in tendon ultimate stress as a result of cyclic loading.…”

Human achilles tendon plasticity in response to cyclic strain: effect of rate and duration

“…Two modes were suggested for the transmission of the external strain to the cellular level: cell deformation and fluid flow-induced shear stress (Lavagnino et al, 2003;Lavagnino et al, 2008). With increasing strain, a loss of collagen crimp and an increase in fiber recruitment was observed (Hansen et al, 2002;Schatzmann et al, 1998) and likely results in an increased number of cells being deformed (Arnoczky et al, 2002). The inhibition of catabolic cell responses (collagenase mRNA) seems to be directly associated with progressive increases of strain magnitude (Arnoczky et al, 2004;Lavagnino et al, 2008;Lavagnino et al, 2003).…”

Tendon material properties vary and are interdependent among turkey hindlimb muscles

“…The sine wave amplitude was set to yield a 4% L 0 excursion for each tendon. The sine wave cycles preconditioned the tendon to avoid changes in EM that are known to occur with initial load cycles in isolated tendons (Schatzmann et al, 1998). Over the last 10 cycles, resilience was calculated as the average proportion of energy conserved between each lengthening-shortening cycle.…”