Viviana Pinto

Influence of pressure-relief insoles developed for loaded gait (backpackers and obese people) on plantar pressure distribution and ground reaction forces

The aims of this study were to test the effects of two pressure relief insoles developed for backpackers and obese people on the ground reaction forces (GRF) and plantar pressure peaks during gait; and to compare the GRF and plantar pressures among normal-weight, backpackers, and obese participants. Based on GRF, plantar pressures, and finite element analysis two insoles were manufactured: flat cork-based insole with (i) corkgel in the rearfoot and forefoot (SLS1) and with (ii) poron foam in the great toe and lateral forefoot (SLS2). Gait data were recorded from 21 normal-weight/backpackers and 10 obese participants. The SLS1 did not influence the GRF, but it relieved the pressure peaks for both backpackers and obese participants. In SLS2 the load acceptance GRF peak was lower; however, it did not reduce the plantar pressure peaks. The GRF and plantar pressure gait pattern were different among the normal-weight, backpackers and obese participants.

Exploring the in vitro and in vivo compatibility of PLA, PLA/GNP and PLA/CNT-COOH biodegradable nanocomposites: Prospects for tendon and ligament applications: BIOCOMPATIBILITY OF PLA/GNP AND PLA/CNT-COOH NANOCOMPOSITES

Anterior cruciate ligament (ACL) reconstructive surgeries are the most frequent orthopedic procedures in the knee. Currently, existing strategies fail in completely restoring tissue functionality and have a high failure rate associated, presenting a compelling argument towards the development of novel materials envisioning ACL reinforcement. Tendons and ligaments, in general, have a strong demand in terms of biomechanical features of developed constructs. We have previously developed polylactic acid (PLA)-based biodegradable films reinforced either with graphene nanoplatelets (PLA/GNP) or with carboxyl-functionalized carbon nanotubes (PLA/CNT-COOH). In the present study, we comparatively assessed the biological performance of PLA, PLA/GNP, and PLA/CNT-COOH by seeding human dermal fibroblasts (HFF-1) and studying cell viability and proliferation. In vivo tests were also performed by subcutaneous implantation in 6-week-old C57Bl/6 mice. Results showed that all formulations studied herein did not elicit cytotoxic responses in seeded HFF-1, supporting cell proliferation up to 3 days in culture. Moreover, animal studies indicated no physiological signs of severe inflammatory response after 1 and 2 weeks after implantation. Taken together, our results present a preliminary assessment on the compatibility of PLA reinforced with GNP and CNT-COOH nanofillers, highlighting the potential use of these carbon-based nanofillers for the fabrication of reinforced synthetic polymer-based structures for ACL reinforcement.

Ligaments’ clamping: a novel solution to prevent soft tissue slippage

The mechanical properties of ligaments are often measured using mounted specimens such as boneligament-bone in a uniaxial tension setup. Numerous experimental studies have been conducted to perform knee ligaments characterization, facing some challenges to reach the ultimate load. The ligaments are soft moist tissues with viscoelastic properties that make its clamping a complex task. Therefore, the main goal was to overcome these difficulties by developing an innovative and functional clamping method. The validation of the proposed solution was done through mechanical characterization of porcine knee ligaments. The design of these customized clamps took into account the soft tissue characteristics. The performance of the clamps was evaluated during mechanical characterization of porcine knee ligaments under tensile loading at three different strain rates. The test results indicated that the cruciate ligaments are the most rigid, whereas the collateral ligaments are the less rigid, in line with published results. In brief, the proposed method and protocol to measure ligaments’ mechanical properties revealed to be effective, reaching the failure load without tissue slippage. DOI: https://doi.org/10.24243/JMEB/2.5.160

Viscoelastic modelling of creep and stress relaxation behaviour in PLA-PCL fibres

In case of high performance athletes, ligaments are the most commonly injured tissues. Current gold standard process for replacement of ligament is autografting. Research in the field of biodegradable polymers (as a possible ligament device) has helped in overcoming the various drawbacks of autografting. Biodegradable blend of polylactic acid and polycaprolactone (PLA-PCL) have been proposed for use in a medical device to repair injured ligaments. By using a mathematical model, this study aims to characterise the non-linear viscoelastic properties of PLA-PCL fibres. In the present study, two modified models were used; the Burger’s model and three-element standard solid model. The model parameters were calibrated by using the tensile and creep experimental data. In case of Burger’s model, the parameters were significantly affected by the stress level. This functional stress dependency was represented by a second degree polynomial. By employing the previously computed parameters, the stress relaxation data of PLA-PCL fibres was used to check the model simulations. Only the predictions generated from the modified three-element standard solid model were found to be in an agreement with the experimental data. This model enables representing the general viscoelastic response of PLA-PCL fibres through a unique set of parameters.