Biomedical subjects

Natalia Juncosa

Publications and source records attributed to Natalia Juncosa.

4 recordsLinked to original sources

PubMed2004

Characterization of in vivo Achilles tendon forces in rabbits during treadmill locomotion at varying speeds and inclinations.

The objective of this study was to test the hypothesis that increasing the speed and inclination of the treadmill increases the peak Achilles tendon forces and their rates of rise and fall in force. Implantable force transducers (IFT) were inserted in the confluence of the medial and lateral heads of the left gastrocnemius tendon in 11 rabbits. IFT voltages were successfully recorded in 8 animals as the animals hopped on a treadmill at each of two speeds (0.1 and 0.3 mph) and inclinations (0 degrees and 12 degrees). Instrumented tendons were isolated shortly after sacrifice and calibrated. Contralateral unoperated tendons were failed in uniaxial tension to determine maximum or failure force, from which safety factor (ratio of maximum force to peak in vivo force) was calculated for each activity. Peak force and the rates of rise and fall in force significantly increased with increasing treadmill inclination (p<0.001). Safety factors averaged 30.8+/-7.5 for quiet standing, 7.0+/-2.9 for level hopping, and 5.2+/-0.7 for inclined hopping (mean+/-SEM). These in vivo force parameters will help tissue engineers better design functional tissue engineered constructs for rabbit Achilles tendon and other tendon repairs. Force patterns can also serve as input data for mechanical stimulation of tissue-engineered constructs in culture. Such approaches are expected to help accelerate tendon repair after injury.

Achilles Tendon↗

PubMed2004

Functional tissue engineering parameters toward designing repair and replacement strategies.

Abnormal joint kinematics and loads induced after soft tissue injuries are assumed to contribute to long-term degenerative joint disease and osteoarthritis. Controlling abnormal kinematics after repair and reconstruction of these injured structures would seem to be important for limiting wear of the articular cartilage surfaces. In this paper, we propose to expand the paradigm of functional tissue engineering to more fully characterize normal joint function and to establish design parameters for soft tissue repair and reconstruction to ultimately protect joint surfaces after surgery. Structure-function relationships are examined for tissues of increasing complexity, from tendons to menisci. Emphasis is placed on understanding normal in vivo function of tissues by conducting biomechanical experiments in vitro that better mimic in vivo conditions. This process yields nine classes of functional tissue engineering parameters: differential fiber length, in vivo force and displacement, variations in relative attachment site locations, loading from adjacent structures, fiber interactions, types of insertion, regional variations in material properties, nonparallel fiber orientations, and complex loading within the structure. These functional tissue engineering parameters are useful not only for understanding the function of normal tissues but for more effectively designing their repair and replacement. This paper concludes with a discussion of research directions that investigators might take to establish tissue-specific functional tissue engineering parameters for improving joint function and reducing articular surface degradation and osteoarthritis.

Humans↗

PubMed2004

Functional efficacy of tendon repair processes.

Despite various attempts to repair and replace injured tendon, an understanding of the repair processes and a systematic approach to achieving functional efficacy remain elusive. In this review the epidemiology of tendon injury and repair is first examined. Using a traditional paradigm for repair assessment, the biology and biomechanics of normal tendon, natural healing, and repair are then explored. New treatment strategies such as functional tissue engineering are discussed, including a functional approach to treatment that involves the development of in vivo functional design parameters to judge the acceptability of a repair outcome. The paper concludes with future directions.

Biomechanical Phenomena↗

PubMed2003

In vivo forces used to develop design parameters for tissue engineered implants for rabbit patellar tendon repair.

Previous studies in tissue engineering have shown that suspending undifferentiated mesenchymal stem cells in collagen gels and wrapping them about a suture causes alignment of cells and contraction of constructs in culture in a form that is suitable for implantation for tendon repair. Little is known about the patterns of these in vivo signals that might improve tendon repair biomechanics. Three hypotheses were tested in this study using the rabbit patellar tendon (PT) model: (1) peak in vivo forces and the rates of rise and fall in these forces will increase significantly with increasing levels of activity; (2) the PTs safety factor for all activities will be in the range of values found for tendons (2.5-3); (3) rabbits will not "favor" the operated limb at the time of evaluation but maintain similar vertical ground reaction forces in both limbs during quiet standing (QS). In vivo rabbit PT forces were measured during QS and while the animal hopped on a treadmill whose speed (0.04 and 0.13 m/s) and inclination (0 degrees and 12 degrees) were controlled. Implantable force transducers were surgically placed in one PT and data collected three days post surgery in each of eight New Zealand White rabbits. Peak tensile forces increased significantly with inclination of the treadmill and the rates of rise and fall in tendon force increased significantly with both speed and inclination (p<0.001). Such design criteria should be useful in mechanically stimulating cell-gel constructs for tendon repair.

Animals↗