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Leuven, Belgium

Famaey N.,Biomechanics Section | Verhoeven J.,University Hospital Gasthuisberg | Jacobs S.,University Hospital Gasthuisberg | Pettinari M.,University Hospital Gasthuisberg | Meyns B.,University Hospital Gasthuisberg
International Journal of Artificial Organs | Year: 2014

Introduction: The purpose of this study was to evaluate the evolution of the mechanical properties of stretchable and non-stretchable ePTFE vascular grafts over time following implantation, as well as those of the adjacent native vessels. Methods: One stretchable and one non-stretchable graft were implanted in either carotid position of six sheep. After twelve weeks, the samples, as well as the distal adjacent native vessel, were explanted and evaluated mechanically by means of uniaxial tensile tests. These tests were performed in the axial as well as in the circumferential direction. Also, patches of these grafts were implanted subcutane-ously in the abdominal wall of the same animals. At 2, 4, 6, and 8 weeks, patches were explanted and evaluated mechanically. Baseline mechanical tensile tests were also performed on non-implanted grafts and on native sheep carotid arteries. Results: Statistical analysis shows a significant effect of implantation time on the tensile mechanical properties of ePTFE vascular grafts. This effect is present for stretchable as well as non-stretchable grafts, in axial as well as in circumferential direction of the material. Also the adjacent native vessels have a tendency to lose mechanical stiffness and strength in the circumferential direction, an effect which is most pronounced for stretchable grafts. Conclusions: The mechanical properties of ePTFE vascular grafts and the adjacent native vessels significantly change as a function of implantation time. Compared to the native vessels, the grafts are still significantly stronger and stiffer, though longer term experiments are needed to evaluate whether and how much the decline would continue in time. © 2014 Wichtig Publishing.

Varon C.,Center for Dynamical Systems | Alao M.,North East London NHS Foundation Trust | Minter J.,North East London NHS Foundation Trust | Stapleton M.,North East London NHS Foundation Trust | And 4 more authors.
Journal of Telemedicine and Telecare | Year: 2015

Telehealth has become a very important tool that allows the monitoring of heart failure patients in a home environment. However, little is known about the effect that such monitoring systems have on patients’ compliance, evolution and self-care behaviour. In particular, the effect that the selected user interface has on these factors is unknown. This study aims to investigate this, and to determine some practicalities that must be considered when designing and implementing a telehealth programme for heart failure. To achieve this, daily measurements of blood pressure, pulse, SpO2 and weight were collected from 534 patients suffering from heart failure. In addition, they were asked to fill in the European heart failure self-care behaviour scale questionnaire and the EQ-5D quality of life questionnaire, before and after the monitoring period. Two telehealth systems were used, the Motiva platform provided by Philips and the standalone unit provided by Docobo, the Doc@Home system. Significant differences were found between both systems concerning the compliance and adherence of patients. Moreover, a general, positive effect of telehealth was identified due to the fact that patients showed an increased self-awareness when managing their condition. These findings are supported by behavioural changes and a better understanding of heart failure from the patients’ perspective. © 2015, © The Author(s) 2015.

Hoenig E.,Biomechanics Section | Winkler T.,Biomechanics Section | Mielke G.,Biomechanics Section | Paetzold H.,Biomechanics Section | And 6 more authors.
Tissue Engineering - Part A | Year: 2011

Adult cartilage has a limited healing capacity. Damages resulting from disease or injury increase over time and cause severe pain. One approach to reinstate the cartilage function is tissue engineering (TE). However, the generation of TE cartilage is time consuming and expensive and its properties are so far suboptimal. As in vivo cartilage is subject to loading, it is assumed that mechanical stimulation may enhance the quality of TE cartilage. In this study the short-term influence of variable compressive strain amplitudes on mechanical and biochemical properties of scaffold-free TE cartilage was investigated. Primary porcine chondrocytes were isolated, proliferated, redifferentiated, and transferred onto hydroxyapatite carriers, resulting in scaffold-free cartilage-carrier constructs. These constructs were placed in a custom-made bioreactor. Compression amplitudes of 5%, 10%, and 20% were applied. In each experiment four constructs were loaded with dynamic compression (3000 cycles/day, 1 Hz) for 14 days and four constructs served as unloaded control. The cartilage was evaluated biochemically, histological, and mechanically. No difference in glycosaminoglycan or collagen content between the loaded and the control groups was found. However, a positive correlation between compression amplitude and normalized Young's modulus was detected (R2=0.59, p<0.001). The highest compression amplitude of 20% had the strongest positive effect on the mechanical properties of the TE cartilage (Young's modulus increase of 241±28% compared to unloaded control). The data presented suggest that preconditioning with higher load amplitudes might be an attractive way of generating stiffer tissue and may help accelerating the cultivation of mechanically competent TE cartilage. © 2011 Mary Ann Liebert, Inc.

Peeters K.,Biomechanics Section | Schreuer J.,Catholic University of Louvain | Burg F.,Biomechanics Section | Burg F.,Catholic University of Leuven | And 6 more authors.
Journal of Orthopaedic Research | Year: 2013

We compared bone and articular morphology of the talus and navicular in clinically diagnosed flatfeet and evaluated their potential contribution to talo-navicular joint instability. We used CT images to develop 3D models of talus and navicular bones of 10 clinically diagnosed flatfeet and 15 non-flatfeet. We quantified their global bone dimensions, inclination and dimensions of the articular surfaces and their curvatures. Additionally, ratios of six talar and navicular dimensions were calculated. The values for these parameters were then compared between both groups. In flatfeet, the talar head faced more proximal and its width was larger compared to non-flatfeet. Also the navicular cup faced more proximal and its depth was significantly increased. Furthermore, we observed a more protruding talar head compared to the navicular cup in the control group with the articular surface depth being relatively larger for the navicular cups when compared to the talus in flatfeet. The ratio of the talar and navicular articular surface height was decreased in flatfeet, suggesting increased height of navicular cups relative to the articulating talar heads. Our results show that flatfoot deformity is associated with morphological changes of talar and navicular articular surfaces that can favor medial arch collapse and forefoot abduction. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 282-287, 2013 Copyright © 2012 Orthopaedic Research Society.

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