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Volume 3, Number 2, June 2016

The finite element method is wide used in simulation in the biomechanical structures, but a lack of studies concerning finite element mesh quality in biomechanics is a reality. The present study intends to analyze the importance of the mesh quality in the finite element model results from humeral structure. A sensitivity analysis of finite element models (FEM) is presented for the humeral bone and cartilage structures. The geometry of bone and cartilage was acquired from CT scan and geometry reconstructed. The study includes 54 models from same bone geometry, with different mesh densities, constructed with tetrahedral linear elements. A finite element simulation representing the glenohumeral-joint reaction force applied on the humerus during 90

Key Words
bone; humerus behavior; finite element analysis; mesh convergence; strain.

Bola, Ana M., Ramos, A.:Biomechanics Research Group, TEMA, University of Aveiro, 3810-193 Aveiro, Portugal

Simões, J. A: High School of Arts and Design, Avenida Calouste Gulbenkian, Matosinhos, Portugal

Stability and loosening of implanted femoral stems in Total Hip Replacement have been well established as barriers to the primary concerns of osseointegration and long term implant survival. In-vitro experiments and finite element modeling have for years been used as a primary tool to assess the bone stem interface with variable methodologies leading to a wide range of micromotion, interference fit and stress shielding values in the literature. The current study aims to provide a comprehensive review of currently utilized methodologies for in-vitro mechanical testing as well as finite element modeling of both micromotion and interference of implanted femoral stems. A total of 12 studies detailed in 33 articles were selected for inclusion. Experimental values of micromotion ranged from 12 to 182

Key Words
femoral stem; micromotion; cadaveric testing; finite element modeling; interference fit

Giovanni F Solitro and Farid Amirouche: Department of Orthopaedic Surgery, University of Illinois at Chicago,
835 South Wolcott Ave. Chicago, IL, USA

Keith Whitlock: College of Medicine, University of Illinois at Chicago, USA

Catherine Santis: Department of Mechanical Engineering, University of Illinois at Chicago, USA

The purpose of this study is to evaluate the effects of cryopreservation on dental pulp-derived stem cells (DPSC) viability over a period of three years. Dental pulp-derived stem cells were isolated and cultured from thirty-one healthy teeth. DPSC isolates were assessed for doubling-time and baseline viability prior to cryopreservation and were assessed again at three time points; one week (T1), 18 months (T2), and 36 months (T3). DPSC can be grouped based on their observed doubling times; slow (sDT), intermediate (iDT), and rapid (rDT). Viability results demonstrated all three types of DPSC isolates (sDT, iDT and rDT) exhibit time-dependent reductions in viability following cryopreservation, with the greatest reduction observed among sDT-DPSCs and the smallest observed among the rDT-DPSC isolates. Cryopreserved DPSCs demonstrate time-dependent reductions in cellular viability. Although reductions in viability were smallest at the initial time point (T1) and greatest at the final time point (T3), these changes were markedly different among DPSC isolates with similar doubling times (DTs). Furthermore, the analysis of various DPSC biomarkers – including both intracellular and cell surface markers, revealed differential mRNA expression. More specifically, the relative high expression of Sox-2 was only found only among the rDT isolates, which was associated with the smallest reduction in viability over time. The expression of Oct4 and NANOG were also higher among rDT isolates, however, expression was comparatively lower among the sDT isolates that had the highest reduction in cellular viability over the course of this study. These data may suggest that some biomarkers, including Sox-2, Oct4 and NANOG may have some potential for use as biomarkers that may be associated with either higher or lower cellular viability over long-term storage applications although more research will be needed to confirm these findings.

Key Words
cryopreservation; human dental pulp-derived stem cells; effect

Allison Tomlin: Advanced Education in Orthodontics and Dentofacial Orthopedics, University of Nevada, Las Vegas–
School of Dental Medicine, 1001 Shadow Lane, Las Vegas, Nevada, 89106-4124, USA

Michael B Sanders: Clinical Sciences, University of Nevada, Las Vegas – School of Dental Medicine,
1001 Shadow Lane, Las Vegas, Nevada, 89106-4124, USA

Karl Kingsley: Biomedical Sciences, University of Nevada, Las Vegas – School of Dental Medicine, 1001 Shadow Lane, Las Vegas, Nevada, 89106-4124, USA

Shoulder pain, injury and discomfort are public health and economic issues world-wide. The function of these joints and the stresses developed during their movement is a major concern to the orthopedic surgeon to study precisely the injury mechanisms and thereby analyze the post-operative progress of the injury. Shoulder is one of the most critical joints in the human anatomy with maximum degrees of freedom. It mainly consists of the clavicle, scapula and humerus; the articulations linking them; and the muscles that move them. In order to understand the behavior of individual muscle during abduction arm movement, an attempt has been made to analyze the stresses developed in the shoulder muscles during abduction arm movement during the full range of motion by using the 3D FEM model. 3D scanning (ATOS III scanner) is used for the 3D shoulder joint cad model generation in CATIA V5. Muscles are added and then exported to the ANSYS APDL solver for stress analysis. Sensitivity Analysis is done for stress and strain behavior amongst different shoulder muscles; deltoid, supraspinatus, teres minor, infraspinatus, and subscapularies during adduction arm movement. During the individual deltoid muscle analysis, the von Mises stresses induced in deltoid muscle was maximum (4.2175 MPa) and in group muscle analysis it was (2.4127MPa) compared to other individual four rotor cuff muscles. The study confirmed that deltoid muscle is more sensitive muscle for the abduction arm movement during individual and group muscle analysis. The present work provides in depth information to the researchers and orthopedicians for the better understanding about the shoulder mechanism and the most stressed muscle during the abduction arm movement at different ROM. So during rehabilitation, the orthopedicians should focus on strengthening the deltoid muscles at earliest.

Key Words
shoulder joint; deltoid; supraspinatus; von Mises stresses; abduction; equivalent elastic strain

Shriniwas. S. Metan: Department of Mechanical Engineering, NK Orchid College of Engineering & Technology,
Solapur, Solapur, India.

G.C. Mohankumar and Prasad Krishna: Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal Karnataka, India

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