Comparison of elastic, viscoelastic and failure tensile material properties of knee ligaments and patellar tendon

Abstract

The knee ligaments and patellar tendon function in concert with each other and other joint tissues, and are adapted to their specific physiological function via geometry and material properties. However, it is not well known how the viscoelastic and quasi-static material properties compare between the ligaments. The purpose of this study was to characterize and compare these material properties between the knee ligaments and patellar tendon. Dumbbell-shaped tensile test samples were cut from bovine knee ligaments (ACL, LCL, MCL, PCL) and patellar tendon (PT) and subjected to tensile testing (n = 10 per ligament type). A sinusoidal loading test was performed at 8% strain with 0.5% strain amplitude using 0.1, 0.5 and 1 Hz frequencies. Subsequently, an ultimate tensile test was performed to investigate the stress-strain characteristics. At 0.1 Hz, the phase difference between stress and strain was higher in LCL compared with ACL, PCL and PT (p < 0.05), and at 0.5 Hz that was higher in LCL compared with all other ligaments and PT (p < 0.05). PT had the longest toe-region strain (p < 0.05 compared with PCL and MCL) and MCL had the highest linear and strain-dependent modulus, and toughness (p < 0.05 compared with ACL, LCL and PT). The results indicate that LCL is more viscous than other ligaments at low-frequency loads. MCL was the stiffest and toughest, and its modulus increased most steeply at the toe-region, possibly implying a greater amount of collagen. This study improves the knowledge about elastic, viscoelastic and failure properties of the knee ligaments and PT.

Strain imaging of the lateral collateral ligament using high frequency and conventional ultrasound imaging: An ex-vivo comparison

“…The grips allowed free motion of the ligament, except for the axial direction ( i.e., rotation and translation perpendicular to the axial loading direction). Specimens were preloaded to 10N to reduce slackness and their initial length was measured (using the image data from the DIC method), followed by a preconditioning step of 10 cycles of axial stretching to 5% at a frequency of 1 Hz ( Ristaniemi et al, 2017 ). Axial stretching was accomplished by displacement driven elongation of the initial measured length of the ligament.…”

A computational homogenization approach for uniaxial stress state analyses of wavy fibrous materials

“…∂ ∂γ The set of nonlinear equations (14) and its derivatives (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) were discretized by the standard finite element method [1], resulting in the residual vector and the tangent matrix of the classical Newton-Raphson algorithm, respectively. An analogous discretization procedure is presented in Carniel et al [7], where one can find further technical details regarding the numerical implementation.…”

“…Tensile tests are widely applied to assess the mechanical behavior of a broad range of composite materials. Particularly for biological fibrous tissues-such as tendons, ligaments, and arteries-tensile tests comprise the main experimental approach to study their mechanical responses [9,17,29]. In this case, the hypothesis of a homogeneous uniaxial stress state could be assumed in some regions of the specimen.…”

Viscoelastic characteristics of the canine cranial cruciate ligament complex at slow strain rates

“…The phenomenon of viscoelastic characteristics including strain rate dependency, hysteresis, creep and stress relaxation has been observed consistently in soft biological tissues such as the sclera (Elsheikh et al, 2010;Geraghty et al, 2020), cornea (Elsheikh et al, 2011;Kazaili et al, 2019), and tendon (Robinson et al, 2004;Zuskov et al, 2020). Similarly, ligaments inherit non-linear viscoelastic characteristics exhibiting both elastic and viscous behaviour, hence they are history-and time-dependent (Bonner et al, 2015;Fung, 1993;Ristaniemi et al, 2018). The initial part of the non-linear load-deformation behaviour in ligaments is the toe region where the wavy collagen fibres become taut and straighten as load is applied, hence the crimp is removed (Fratzl et al, 1998).…”

“…However, a study on rabbit medial collateral ligament complexes at varying strain rates (between 0.66 and 9300 %/min) showed that the ligaments were only minimally strain rate dependent (Woo et al, 1990b(Woo et al, , 1981. The small effect of strain rate stiffening could be because the studies combined stress-strain characteristics at the toe region with the elastic region (Haut and Little, 1969;Ristaniemi et al, 2018).…”