Compressive moduli of the human medial meniscus in the axial and radial directions at equilibrium and at a physiological strain rate

Abstract

The axial and radial compressive moduli of the human meniscus are important material properties in tibiofemoral joint models, but they have not been determined previously for fresh-frozen tissue. Our goals were to measure the moduli at equilibrium and at a physiological strain rate, to determine whether the axial and radial compressive moduli are equal for each type of loading, and to determine whether they depend on the region (i.e., anterior, middle, posterior) of the meniscus. Samples from each region from 10 fresh-frozen human medial menisci were tested in unconfined compression at four strain levels (3%, 6%, 9%, and 12%) at 32%/s, a strain rate determined to be physiologically relevant to walking, and then allowed to reach equilibrium in stress relaxation. At equilibrium, the axial and radial compressive moduli at 12% strain were 83.4 kPa and 76.1 kPa, respectively (p ¼ 0.58), whereas at the physiological strain rate, the axial and radial compressive moduli at 12% strain were 718 kPa and 605 kPa, respectively (p ¼ 0.61). At the physiological strain rate, the modulus increased with increasing strain (79.2 kPa at 3% strain vs. 662 kPa at 12% strain) and the modulus in the anterior region (1,048 kPa at 12% strain) was significantly greater than that in the posterior region (329 kPa at 12% strain) (p ¼ 0.04). Our study supports a plane of isotropy for the material properties of meniscal tissue. However, the material behavior is strongly nonlinear because the compressive modulus is several orders of magnitude smaller than previously reported values for tensile modulus. Further, the compressive modulus depends on the activity of interest (i.e., static such as standing or dynamic such as walking) due to viscoelastic effects, the strain level, and the region of the tissue. ß

Comparison of osmotic swelling influences on meniscal fibrocartilage and articular cartilage tissue mechanics in compression and shear

“…The results are consistent with previous observations of tissue behaviors, including increased compressive 22 and shear 23 moduli of meniscal tissue with increasing compressive offset, increased shear moduli of cartilage with increasing compressive offset and decreasing bath salinity, 17 and greater shear modulus for circumferential samples than for axial samples. 23 It should be noted that, while consistent with other values in the literature, 9,13,22,23 the moduli measured for meniscal tissue are quite low.…”

Evaluation of Meniscal Mechanics and Proteoglycan Content in a Modified Anterior Cruciate Ligament Transection Model

“…Because mechanical and histological properties have been seen to be regionally dependent [22,[43][44][45], each meniscus was sectioned into anterior, central, and posterior regions for testing. Specimens were kept hydrated with 0.9% phosphate buffered saline (PBS) solution before and during mechanical testing.…”

Optimizing gelling parameters of gellan gum for fibrocartilage tissue engineering

“…To put these data into perspective, typical compressive moduli for native tissue are: nucleus pulposus, 3-310 kPa [33][34][35] ; annulus fibrosus, 29-740 kPa [34][35][36] ; articular cartilage, 0.31-1.237 MPa [37][38][39] ; and meniscus, 0.605-1.03 MPa. 40,41 From these compressive modulus values of native tissues, the 5-6% (w/v) low acyl gellan gum with complex compressive moduli of 324.1 6 6.3 and 407.9 6 10.0 kPa, respectively could be a good candidate for nucleus pulposus and annulus fibrosus replacement, and nearly sufficient for meniscus. Unfortunately, at these concentrations of gellan gum the gelling temperature is too high for its use as a scaffold for cells ($55-65 C).…”