Strain-rate-dependent non-linear tensile properties of the superficial zone of articular cartilage.
OBJECTIVE
The tensile properties of articular cartilage play an important role in the compressive behavior and integrity of the tissue. The stress-strain relationship of cartilage in compression was observed previously to depend on the strain-rate. This strain-rate dependence has been thought to originate mainly from fluid pressurization. However, it was not clear to what extent the tensile properties of cartilage contribute to the strain-rate dependence in compressive behavior of cartilage. The aim of the present study was to quantify the strain-rate dependent stress-strain relationship and hysteresis of articular cartilage in tension.


METHODS
Uniaxial tensile tests were performed to examine the strain-rate dependent non-linear tensile properties of the superficial zone of bovine knee cartilage. Tensile specimens were oriented in the fiber direction indicated by the India ink method. Seven strain-rates were used in the measurement ranging from 0.1 to 80%/s, which corresponded to nearly static to impact joint loadings.


RESULTS
The experimental data showed substantial strain-rate and strain-magnitude dependent load response: for a given strain-magnitude, the tensile stress could vary by a factor of 1.95 while the modulus by a factor of 1.58 with strain-rate; for a given strain-rate, the modulus at 15% strain could be over four times the initial modulus at no strain. The energy loss in cartilage tension upon unloading exhibited a complex variation with the strain-rate.


CONCLUSIONS
The strain-rate dependence of cartilage in tension observed from the present study is relatively weaker than that in compression observed previously, but is considerable to contribute to the strain-rate dependent load response in compression.
a Department of Mechanical and Manufacturing Engineering , University of Calgary , Calgary , Alberta , Canada.
Sahand
S
Ahsanizadeh
a Department of Mechanical and Manufacturing Engineering , University of Calgary , Calgary , Alberta , Canada.
LePing
L
Li
D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry*; D002417:Cattle; D013314:Stress, Mechanical; D013718:Tensile Strength
Bovine knee cartilage; collagen viscoelasticity; hysteresis; strain-rate dependent property; tensile test