Collagen Fiber Alignment and Maximum Principal Strain in the Glenohumeral Capsule Predict Location of Failure During Uniaxial Extension

The glenohumeral joint is frequently dislocated causing injury to the glenohumeral capsule (axillary pouch (AP), anterior band of the inferior glenohumeral ligament (AB-IGHL), posterior band of the inferior glenohumeral ligament (PB-IGHL), posterior (Post), and anterosuperior region (AS)). [1, 2] The capsule is a passive stabilizer to the glenohumeral joint and primarily functions to resist dislocation during extreme ranges of motion. [3] When unloaded, the capsule consists of randomly oriented collagen fibers, which play a pertinent role in its function to resist loading in multiple directions. [4] The location of failure in only the axillary pouch has been shown to correspond with the highest degree of collagen fiber orientation and maximum principle strain just prior to failure. [4, 5] However, several discrepancies were found when comparing the collagen fiber alignment between the AB-IGHL, AP, and PB-IGHL. [3,6,7] Therefore, the objective was to determine the collagen fiber alignment and maximum principal strain in five regions of the capsule during uniaxial extension to failure and to determine if these parameters could predict the location of tissue failure. Since the capsule functions as a continuous sheet, we hypothesized that maximum principal strain and peak collagen fiber alignment would correspond with the location of tissue failure in all regions of the glenohumeral capsule.

Experimental and Numerical Flow Visualization in Patient Specific Pre Operative Human Airway Geometry

An experimental and numerical platform was developed to investigate the fluidodynamics in human airways. A pre operative patient specific geometry was used to create an identical experimental and numerical model. The experimental results obtained from Particle Image Velocimetry (PIV) measurements were compared to Computational Fluid Dynamics (CFD) simulations under stationary and pulsatile flow regimes. Together these results constitute the first step in predicting the clinical outcome of patients after lung surgeries such as Lung Volume Reduction.

Innovative Scaffold Design for Soft Tissue-to-Bone Interface Tissue Engineering

Soft tissue-based ACL reconstruction grafts are limited by their inability to reestablish a functional interface with bone tissue[1–2]. The native ACL-bone interface consists of three regions: ligament, fibrocartilage, and bone[3–5]. Graft integration is a critical factor governing its clinical success, and the regeneration of an anatomic interface on synthetic or biological ACL grafts will improve clinical outcome. Our interface tissue engineering effort has focused on biomimetic scaffold design to recapitulate the inherent complexity of the ligament-to-bone interface and ultimately, to guide interface regeneration. To this end, we have designed a tri-phasic scaffold comprised of three distinct yet continuous phases, each designed for the formation of a specific tissue type found at the ACL-to-bone interface, as well as a bi-phasic collar to promote the formation of fibrocartilage on ACL reconstruction grafts and also enhance osteointegration.

Determination of Mechanical Stresses in Vibration and Contact During Flow-Structure-Interaction in Vocal Folds

Mechanical stresses in vocal folds (VFs) developed during self-oscillation — due to interaction with the glottal flow — play an important role in tissue damage and healing. Contact stresses occurring due to collision between VFs modify both self-oscillation characteristics, as well as stresses. The complexity of the problem is increased due to other factors acting in combination: transient nature of the flow, non-linear and anisotropic biomechanical properties of the VFs, and acoustic loading. Experiments with physical models [1] have attempted to deduce the state of stress in the interior through measurement of superior surface deformation. However, these methods pose challenges in data acquisition. on the other hand, full three-dimensional transient computational analysis of a self-oscillating and contacting VF model requires highly sophisticated algorithms as well as prohibitive resource usage. Not surprisingly, therefore, it has not been conducted until now. We hypothesize that a high-fidelity numerical simulation incorporating realistic tissue properties is essential to accurately determine stresses within VFs during self-oscillation and contact.

Contrast-Free Blood Flow Velocity Profile Measurement With Ultrasound in Real-Time

In clinical practice, ultrasound is frequently used as a non-invasive method to estimate geometric properties of large arteries such as diameter and intima-media wall thickness and in a separate Doppler measurement hemodynamic variables such as blood velocity. For the purpose of deducing biomechanical parameters and hemodynamic variables that are related to the development of Cardiovascular Disease, such as compliance and vascular impedance, the assessment of only geometry and blood velocity is not sufficient. A simultaneous and non-invasive assessment of blood flow and blood pressure is required. This can only be obtained by an accurate and simultaneous measurement of the blood velocity distribution and wall motion, which is not feasible with the commonly used Doppler technique.

Cervical Spine Movement Sequencing During Flexion-Extension

Static flexion-extension x-rays are the most common clinical tool used to assess abnormal motion of the cervical spine. Despite their widespread use (over 168,000 cases per year), the clinical efficacy of flexion-extension radiographs of the cervical spine has yet to be proven1. Limitations of static flexion-extension x-rays include data collection during static positions that may not accurately represent dynamic behavior, and the fact that data is collected at end range of motion positions, not in more frequently encountered mid-range positions. Consequently, static x-rays may not reveal movement abnormalities that occur during activities of daily living and lead to pain and degeneration. Therefore, it may be advantageous to analyze cervical spine kinematic data collected during dynamic, functional movements performed through an entire range of motion (not just the endpoints). Furthermore, the literature confirms there is substantial variability in “normal” range of motion and translation during flexion-extension1, making it difficult to reliably identify abnormal motion. Therefore, it may also be beneficial to evaluate alternative motion parameters that may reliably identify abnormal motion.

Nonlinear Vocal Fold Dynamics in a Two-Mass Model of Speech Arising From Asymmetric Intraglottal Flow

Voiced speech is initiated as air is expelled from the lungs and passes through the vocal tract inciting self-sustained oscillations of the vocal folds. While various approaches exist for investigating both normal and pathological speech, the relative inaccessibility of the vocal folds make multi-mass speech models an attractive alternative. Their behavior has been benchmarked with excised larynx experiments, and they have been used as analysis tools for both normal and disordered speech, including investigations of paralysis, vocal tremor, and breathiness. However, during pathological speech, vocal fold motion is often unstructured, resulting in chaotic motion and a wealth of nonlinear phenomena. Unfortunately, current methodologies for multi-mass speech models are unable to replicate the nonlinear vocal fold behavior that often occurs in physiological diseased voice for realistic values of subglottal pressure.

Simulated Deployment of Percutaneous Transvenous Mitral Annuloplasty Device Into Human Coronary Sinus Vessel

Functional mitral regurgitation (MR) is the consequence of left ventricular dysfunction occurring after ischemic heart disease and often has poor prognosis. Surgical repair and replacement of the mitral valve are currently being used to treat severe functional MR However, the technique carries high mortality rate [1] and is not suitable for patients with comorbidities and advanced age [2]. Recently, a new non-surgical intervention, percutaneous transvenous mitral annuloplasty (PTMA), is emerging as an attractive endovascular alternative that is less invasive, less recovery time, and cost effective. The device is delivered percutaneously into the coronary sinus (CS) vessel and once embedded, it contracts and shortens the septo-lateral distance of the mitral annulus, hence improve MR. However, despite of its feasibility, current clinical trials reported severe adverse events, such as device fracture [3]. The biomechanical interaction between the CS wall and the stent plays a critical role in the outcome of the deployment and the device performance. In this study, we proposed to analyze this interaction by developing Finite Element (FE) models of the CS vessel and the PTMA anchors and analyzing the peak stresses, strains, interaction forces (shear, normal) after the deployment of the proximal and distal anchors into a realistic patient-specific CS model.

Biotransport Education: Thermal Therapies

Thermal therapies are important clinical modalities in patient treatment that range from long term lower temperature heating for physical therapy and tumor hyperthermia therapy to very high temperature extremely short term heating for surgery. Heat sources that are typically applied include surface contact conduction heat transfer devices, lasers, and electromagnetic field sources from 500 kHz to 2.45 GHz. Their analysis using the classical bioheat equation has proven to be an effective and useful approach to treatment planning, experiment modeling, and new device development efforts.

The Effect of Cyclic Hydrostatic Pressure on the Functional Development of Cartilaginous Tissues Engineered Using Bone Marrow Derived Mesenchymal Stem Cells

Articular cartilage has a poor capacity for repair. Of the many procedures available to the orthopaedic surgeon, osteochondral grafting is the only technique which reliably produces hyaline cartilage within a defect.1 Bone marrow derived mesenchymal stem cells (MSCs) are an interesting alternative to harvesting cartilage grafts for chondrocytes as they also have the ability to produce cartilaginous tissues in vitro. This suggests that if tissue engineering strategies could be used to develop cartilaginous grafts with mechanical properties approaching that of normal articular cartilage, then hyaline tissue could be regenerated. Of concern with such approaches are reports that the mechanical properties of cartilaginous tissues engineered using MSCs are inferior to that engineered using chondrocytes derived from articular cartilage, although recent studies have demonstrated that adult equine MSCs produce a cartilaginous tissue mechanically superior to that derived using animal-matched adult chondrocytes.2