Dynamic compression of human and ovine meniscal tissue compared with a potential thermoplastic elastomer hydrogel replacement.

Understanding how human meniscal tissue responds to loading regimes mimetic of daily life as well as how it compares to larger animal models is critical in the development of a functionally accurate synthetic surrogate. Seven human and eight ovine cadaveric meniscal specimens were regionally sectioned into cylinders 5 mm in diameter and 3 mm thick along with 10 polystyrene-b-polyethylene oxide block copolymer-based thermoplastic elastomer (TPE) hydrogels. Samples were compressed to 12% strain at 1 Hz for 5000 cycles, unloaded for 24 h, and then retested. No differences were found within each group between test one and test two. Human and ovine tissue exhibited no regional dependency (p < 0.05). Human samples relaxed quicker than ovine tissue or the TPE hydrogel with modulus values at cycle 50 not significantly different from cycle 5000. Ovine menisci were found to be similar to human menisci in relaxation profile but had significantly higher modulus values (3.44 MPa instantaneous and 0.61 MPa after 5000 cycles compared with 1.97 and 0.11 MPa found for human tissue) and significantly different power law fit coefficients. The TPE hydrogel had an initial modulus of 0.58 MPa and experienced less than a 20% total relaxation over the 5000. Significant differences in the magnitude of compressive modulus between human and ovine menisci were observed, however the relaxation profiles were similar. Although statistically different than the native tissues, modulus values of the TPE hydrogel material were similar to those of the human and ovine menisci, making it a material worth further investigation for use as a synthetic replacement.