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

Abstract

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 8 ovine cadaveric meniscal specimens were regionally sectioned into cylinders 5mm 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 hours, 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 (3.44MPa instantaneous and 0.61MPa after 5000 cycles compared to 1.97MPa and 0.11MPa found for human tissue) and significantly different power law fit coefficients. The TPE hydrogel had an initial modulus of 0.58MPa 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.

Mechanical viability of a thermoplastic elastomer hydrogel as a soft tissue replacement material

“…The elastic moduli, determined at equilibrium from 3 separate relaxation tests, were significantly lower than the instantaneous response (Figure 2) with the average relaxation across all samples being 12.6%. While the soft tissues of meniscus and articular cartilage display a similar property, the magnitude of relaxation is greater (Fischenich et al, 2017). Meniscal tissue has been found to relax 50–90% (Predrag Bursac et al, 2009; Chia and Hull, 2008; Moyer et al, 2013) and articular cartilage has been reported to relax 40–80% (Hayes and Mockros, 1971; Julkunen et al, 2008; Wilson et al, 2006).…”

Effect of network connectivity on the mechanical and transport properties of block copolymer gels

“…These properties consequently afford gels the capacity to satisfy a number of applications. Such applications include flexible electronics and fuel cells, 1,2 3D printable media, 3 filtration of both liquid 4 and gaseous 5 media, and biomedical applications including soft tissue replacement, 6,7 and drug‐delivery vehicles 8,9 . While hydrogels have fulfilled several of these roles, particularly in the realm of drug delivery, lesser‐studied organogels are also capable of satisfying many of these applications 10–13 and have even been proposed recently as transdermal drug delivery devices 14,15 .…”

Biodegradable crosslinked polyesters derived from thiomalic acid and S-nitrosothiol analogues for nitric oxide release

“…50 Additionally, the instantaneous or dynamic moduli of ovine meniscus at 0.6 MPa is also within range of PTCO and PTCO–NO. 51, 52 In all cases, except for PTMO–NO, the crosslinking density increased for the S -nitrosated polymers. These crosslinking events may be the result of disulfide formation through the thiol-bearing, thiomalic acid, as NO is released from the sample.…”