Dynamic Splints, Functionally-Customized With Nitinol, Can Reduce Joint Rigidity in Pediatric Subjects With Spasticity

Neuromuscular diseases as a consequence of brain damage are complex phenomena involving disuse, immobility, brain tissue remodeling and cortical function remapping. They may have various causes and strike any part of the population. The vicious circle leading to a worsening of the patients’ conditions proceeds through muscle shortening by contractures, disruption of the normal reflex behavior and sensory problems, development of spasticity [1]. Physical rehabilitation alone or in association with surgery or pharmacological treatments can be useful in limiting those degenerations. Besides manual rehabilitation, splints and braces are prescribed to control the limb posture and obtain stretching of the muscles. The role of those orthoses is to maintain the paretic limb in a set ‘physiological’ position and let it relax into that posture, in an attempt to reduce muscle rigidity and contractures. However applying a fixed constraint to the limb and waiting for relaxation to take place, may cause discomfort, pain, skin rash, and sundry different complications [2]. Also, any residual voluntary movement is prevented by a fixed-angle splinting. In addition, all these negative characteristics limit tolerability and daily application times. This work presents a different way to promote limb repositioning, based on the application of NiTi-alloy-based dynamic splints, which favor mobility and any residual use of the affected limb. Furthermore it suggests that application of mild contact forces prolonged in time has the advantage of feeling less painful and uncomfortable for the patients, improving overall treatment tolerability.

Continuum Description of the Time- and Strain-Dependent Poisson’s Ratio of Ligament Under Finite Deformation

Ligament volumetric behavior controls fluid and thus nutrient movement as well as the mechanical response of the tissue to applied loads. The reported Poisson’s ratios for tendon and ligament subjected to tensile deformation loading along the fiber direction are large, ranging from 0.8 ± 0.3 in rat tail tendon fascicles [1] to 2.98 ± 2.59 in bovine flexor tendon [2]. These Poisson’s ratios are indicative of volume loss and thus fluid exudation [3,4]. We have developed micromechanical finite element models that can reproduce both the characteristic nonlinear stress-strain behavior and large, strain-dependent Poisson’s ratios seen in tendons and ligaments [5], but these models are computationally expensive and unfeasible for large scale, whole joint models. The objectives of this research were to develop an anisotropic, continuum based constitutive model for ligaments and tendons that can describe strain-dependent Poisson’s ratios much larger than the isotropic limit of 0.5. Further, we sought to demonstrate the ability of the model to describe experimental data, and to show that the model can be combined with biphasic theory to describe the rate- and time-dependent behavior of ligament and tendon.

A Multiscale Approach to Modeling the Passive Mechanical Contribution of Cells in Tissues

In addition to their obvious biological roles in tissue function, cells often play a significant mechanical role through a combination of passive and active behaviors. Phenomenological and continuum modeling approaches to understand tissue biomechanics have included improved constitutive laws that incorporate anisotropy in the extracellular matrix (ECM) and/or cellular phenomenon, e.g, [1]. The lack of microstructural detail in these models, however, limits their ability to explore the respective contributions and interactions between different components within a tissue. In contrast, structural approaches attempt to understand tissue biomechanics by incorporating microstructural details directly into the model, e.g., the tensegrity model [2], cellular solids models [3], or biopolymer models [4]. Research in our group focuses on developing a comprehensive model to predict the mechanical behavior of soft tissues via a multiscale approach, a technique that allows integration of the microstructural details of different components into the modeling framework. A significant gap in our previous models, however, is the absence of cells. The current work represents an improvement of the multiscale model via the addition of cells, and investigates the passive mechanical contribution of cells to overall tissue mechanics.

Energy Storing and Positional Tendon Fascicles Exhibit Different Fatigue Behaviour

Overuse tendinopathies are often considered to be the result of repeated microstrain below the failure threshold, analogous to the fatigue failure of materials under repeated loading [1, 2]. Investigation of tendon overuse in vitro is thus of potential benefit towards characterizing the progression of damage.

Anti-Adhesions Properties of Polyelectrolyte Complex Based Films

Adhesions are abnormal fibrous connections between tissues and can occur following virtually any type of surgery (1). They are often painful and can severely disrupt normal organ function. The incidence of adhesions following surgery is very high; some estimate an incidence as high as 80%. Thus, the prevention of adhesions has the potential to save the healthcare market billions of dollars and improve the lives of hundreds of thousands of patients.

Method for Incorporating Three-Dimensional Residual Stresses Into Patient-Specific Simulations of Arteries

Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to extract patient-specific geometries from medical images of, e.g., abdominal aortic aneurysms (AAAs), and thus to study clinically relevant problems via FE simulations. Medical imaging is most often performed in vivo, and hence the reconstructed model geometry in the problem of interest will represent the in vivo state, e.g., the AAA at physiological blood pressure. However, classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from an unloaded, stress-free reference condition.

Inclusion of a Collagen-GAG Sponge Core Improves Tangent Modulus of Multi-Phase PEGDM Hydrogel Constructs

Nearly 27 million people in the United States suffer from osteoarthritis (OA).[1] While surgical options are available for patients suffering from OA, focal treatments, such as resection and mosaicplasty, rarely succeed in regenerating fully functional cartilage. Tissue engineering holds potential for developing more effective repair strategies.

Adapting the Cassini Curve to Approximate In Vivo Irreversible Electroporation Ablations in Porcine Liver

Irreversible electroporation (IRE) is a new minimally invasive non-thermal focal ablation technique that has been used for the treatment of spontaneous tumors in canine and human patients [1, 2]. The procedure typically involves placing two electrodes into or around a tumor and delivering a series of low energy electric pulses to kill tumor tissue with sub-millimeter resolution. The pulses generate an electric field that alters the resting transmembrane potential (TMP) of the cells. Depending on the magnitude of the induced TMP, the electric pulses can have no effect, reversibly increase membrane permeability, or cause cell death in the case of IRE.

Meniscal Allografts: Biomechanical Consequences of Different Methods of Fixation

Complete removal of the meniscus (meniscectomy) often leads to early-onset of osteoarthritis due to changes in contact mechanics 1,2. To counteract these changes, the removed meniscus is often replaced with an allograft. Many variables can affect the surgical outcome of meniscal transplantation (bone geometry, graft size, fixation technique, level of activity, limb alignment, etc.) 3,4,5. Among them, the method of fixation is the most readily controlled. Two commonly used techniques are: (i) trans-osseous suture fixation via bone plugs, where bone plugs are machined at the anterior and posterior horns of the graft and implanted into appropriately sized tibial bone tunnels, and (ii) suture fixation at the meniscal horns, where the sutures are drawn through tibial bone tunnels and tied over a bone-bridge. But the mechanical consequences of these fixation techniques, specifically, how they affect knee mechanics are unclear.

The Impact of Mesh Implantation on Vaginal Smooth Muscle Innervation and Contraction

Pelvic organ prolapse (POP) is a multifactorial disorder characterized by the descent of the pelvic organs into the vaginal canal. This disorder is associated with decreased quality of life, and even depression, yet 50% of women over the age of fifty are living with POP. The cost associated with the repair of POP exceeds one billion dollars annually, in the United States alone. This rather exorbitant figure includes the cost of surgery performed for symptom management, but does not include strategies which address the underlying cause of the disorder for which there are none. Because failure rates of native tissue repairs are as high as 30%, vaginal mesh is increasingly used in the surgical repair of POP. The procedure aims to reinforce the fibromuscular layer of the vagina and the paravaginal attachments, thus providing structural integrity to the weakened native tissues. However, the use of mesh is limited by mesh-related complications including exposure, erosion, pain contraction and infection.