Biomechanical comparison of menisci from different species and artificial constructs

Background: Loss of meniscal tissue is correlated with early
osteoarthritis but few data exist regarding detailed biomechanical
properties (e. g. viscoelastic behavior) of menisci in different
species commonly used as animal models. The purpose of the current
study was to biomechanically characterize bovine, ovine, and
porcine menisci (each n = 6, midpart of the medial meniscus) and
compare their properties to that of normal and degenerated human
menisci (n = 6) and two commercially available artificial scaffolds
(each n = 3). Methods: Samples were tested in a cyclic, minimally
constraint compression-relaxation test with a universal testing
machine allowing the characterization of the viscoelastic
properties including stiffness, residual force and relative sample
compression. T-tests were used to compare the biomechanical
parameters of all samples. Significance level was set at p <
0.05. Results: Throughout cyclic testing stiffness, residual force
and relative sample compression increased significantly (p <
0.05) in all tested meniscus samples. From the tested animal
meniscus samples the ovine menisci showed the highest biomechanical
similarity to human menisci in terms of stiffness (human: 8.54 N/mm
+/- 1.87, cycle 1; ovine: 11.24 N/mm +/- 2.36, cycle 1, p =
0.0528), residual force (human: 2.99 N +/- 0.63, cycle 1 vs. ovine
3.24 N +/- 0.13, cycle 1, p = 0.364) and relative sample
compression (human 19.92\% +/- 0.63, cycle 1 vs. 18.72\% +/- 1.84
in ovine samples at cycle 1, p = 0.162). The artificial constructs
- as hypothesized- revealed statistically significant inferior
biomechanical properties. Conclusions: For future research the use
of ovine meniscus would be desirable showing the highest
biomechanical similarities to human meniscus tissue. The
significantly different biomechanical properties of the artificial
scaffolds highlight the necessity of cellular ingrowth and
formation of extracellular matrix to gain viscoelastic properties.
As a consequence, a period of unloading (at least partial weight
bearing) is necessary, until the remodeling process in the scaffold
is sufficient to withstand forces during weight bearing.