Day 3 :
- Biomechanical Materials and Implant Designs
- Biomechanics of the Human Neuromusculoskeletal System
- Biomechanical Devices
OrthoKinetic Technologies, LLC
Southport, North Carolina
Title: Titanium Truss Structures as Conduits for Bone Healing Through Multiplanar Stress Distribution
Time : 10:00-10:25
Introduction: Truss designs are composed of triangular units connected at nodes to provide multiple planes of structural stability. The triangle will not change shape when the lengths of the sides are fixed, resulting in ability to resist significant axial forces. Forces and reactions to them are considered to act only at the nodes and result in forces in the members which are either tensile or compressive, where bending or rotational moments are explicitly excluded, thus bending or rotational moments are expressed as stress transfer to surrounding substrate located at the truss interfaces. This function makes the truss a viable structure for orthopedic devices that are constantly exposed to bending moments, where the greatest moments can occur at the terminal endpoints of devices. A three-dimensional titanium truss structure was fabricated through additive manufacturing techniques to create a multidimensional load bearing scaffold for structural support and fusion incorporation in orthopedic applications. The aim of this study was to develop a series of titanium scaffolds composed of multiplanar truss structures to assess structural integrity and stress distribution for orthopedic use. A comprehensive battery of mechanical tests and validated finite element models [FEA] were performed to determine the load bearing strength and endurance characteristics, as well as the stress profiles distributed throughout the truss structures under multiplanar loading. Methods: Static and dynamic fatigue tests of multiple truss structures with different strut diameters were conducted to measure the yield and ultimate strength and fatigue endurance load limits for multiple planes of physiological motion. FEA models were constructed and loading on each structure mimicked the actual mechanical testing, followed by a validation of each model with the actual test results. Once the models were validated, they were loaded in multiple planes to provide a profile of stress distribution throughout the truss structures. Results: Mechanical results of the truss structures exhibited yield and ultimate strength, stiffness, and fatigue endurance at loads of at least 10 to 15 times stronger than physiological loads in all planes of loading. The open architecture of the truss structure counteracted the high global stiffness measured by distributing stresses across a much greater surface area in multiaxial planes than that of traditional titanium implants, thus reducing the potential for stress risers at the bone interface. The FEA demonstrated stress transfer to truss units deep within the implant, as well as on the surfaces, for all planes of physiological loading. Conclusions: This study found the strength of the truss structure combined with its open architecture created an ideal scaffold that distributed multiplanar forces (stress) throughout the truss formations to all interfaces of the bone surrounding each strut. The end result is a mechanically sound structure with improved stress distribution to the superficial and deeper truss structures. This increased stress transfer is non-destructive to its mechanical integrity and will theoretically result in greater transfer of microstrain to the bone it contacts. Although not the topic of this abstract, an early in vivo animal study assessing bone fusion through these truss structures in sheep intervertebral discs found structurally sound remodeled bone at early time periods. These results potentially support this theory of stress-strain transfer to individual struts within truss structures, which lead to potentially earlier bone incorporation which may promote earlier global stabilization across a bone defect, resulting in augmented bone recruitment.
Abigail Jaitman is a last year Doctoral candidate at Warwick University, UK. Her main area of research is Biomechanics and how it is affected by diabetes; using electromyography, motion capture, plantar pressure and image processing to support state space models. She holds a 6-year BSc in Electronic Engineering from University of Belgrano, Argentina. Since 2009 she has been doing research on Dosimetry (Medical equipment CONICET – UB), and since 2011 is Research Assistant for Dr. Rojas (RSNA & ESR) working on the Mammographic field. She presented at conferences: ECR 2014, PGBiomed/ISC 2014, XIX ICMMB, ECR 2015 and recently published in JMMB.
The difficulties arising in foot modeling are inherent in its complex composition. Most models simplify the foot geometry, structure, materials and kinetic analysis. To overcome this challenge, in this study a new approach is presented, combining gait analysis, plantar pressure and image processing together with biomechanical principles to develop a multi-segment foot model. The model consists of four segments (Phalanges, Midfoot+Metatarsals, Calcaneus, Talus) to represent the foot according to its function, and a fifth segment for the rest of the body. In order to support the model in terms of geometry and parameterization, 10 series of healthy feet images (X-rays, CT and MRI provided by UHCW consultants) were analyzed. Arch height was calculated from motion capture experiments (10 subjects) and the ground reaction force distribution throughout the gait cycle was obtained through plantar pressure analysis on different subjects (14), all experiments complying with data protection requirements. The plantar soft tissue is modeled as system parallel spring dampers. The model considers four relevant joints: Metatarsophalangeal, Transversetarsal, Talocalcaneal and Taloclural. Regarding muscle activation, 13 muscles (both extrinsic and intrinsic) are included using modified Hill muscle model, composed by a contractile element, spring and damper in parallel, to model the muscle, in series with another spring, the latter to model the free tendon. In order to find a set of fitted parameter values for the stiffness and damping coefficients, parameter estimation and optimization is applied on per-subject basis, yielding a minimum absolute error between the measured and simulated trajectories for the model’s joints.
University of Porto
Time : 11:10-11:35
Natacha Rosa worked as a Researcher in Faculty of Engineering, University of Porto between September 2011 – December 2012. Currently she is working as PhD grant holder (FCT) Faculty of Engineering, University of Porto
Intramedullary nailing is one of the oldest types of surgical fracture treatment and is now considered a standard procedure for the surgical management in most tibia diaphysis fractures treatment. Although bone has a unique capability to repair following trauma, it is well accepted that the mechanical conditions at the fracture site influence the healing outcome. The inter fragmentary motions are greatly determined by the stability of the bone-implant assembly and also the nature and magnitude of the loads applied to the limb. This study consists in a biomechanical evaluation of the stability of a tibia-intra medullary nail construction model and the amount of inter fragmentary movements, as closely as possible to the physiological loading conditions for partial-weight bearing which may occurs during a patient’s early recovery stage. To avoid inconsistency of cadaveric bone samples, a synthetic bone model was used in the independent load cases experiments to determine the three-dimensional stability of the assembly. This study allowed a better understanding about intra medullary nail fixation devices configuration, the amount of inter fragmentary motion that occurs during patients early healing phase, and will help develop future strategies to improve intra medullary nail implants for a more favorable mechanical healing environment to occur.
Fatima Abu Baker Hamad is a PhD student in Molecular Biology, Institute of Endemic Diseases, at the University of Khartoum (2012-2016), an MS in Biochemistry & Nutrition from Gezira University, and a BS in Biochemistry & Nutrition from Khartoum University. She is particularly a member in Sudanese Cancer Research Group, Sudanese Environment conservation Society-Wad Madani Branch and member in RAMA Society for cancer patient’s aid- National Cancer Institute (NCI), Gezira University. She published and presented different scientific papers in more than 10 conferences all over the world. She is focused on agriculture communities, chemical contamination, occupations, environments and cancer risk factors.
The rapidly increasing incidence of prostate cancer in Sudan calls for attention to the etiologic and prevention of this type of cancer in old men. Potential risk factors that are mentioned in Sudanese prostate cancer patients are age, education level, unhealthy habits, the body mass index and occupation. A population based case–control study recruited 237 men with a diagnosis of confirmed prostate Cancer and 237 controls randomly selected from the community. Thirteen occupations and 8 industries were selected for analyses to estimate the odds ratio between each occupational circumstance and prostate cancer with control for potential confounders. History of farmer was associated with a highly significant increased the risk for prostate cancer OR (3.711; 95% CI, 2.722-5.058), as was exposure to pesticides was associated with a highly significant increased OR (3.512; 95% CI, 2.611-4.725, P<0.000). Agriculture industry were strongly significantly elevated the risk for prostate cancer, as well as miscellaneous services wasn’t associated but it had significant affected OR (3.439 and 0.506; respectively, P<0.000). Farmer and Horticulturalists, mixable workers and Businessmen were relatively high odds ratios; also these were high statistically significant (P<0.000). These results suggest positive associated was appeared between some occupations, industries and increased the risk for prostate cancer in Sudan. Furthermore it needs more attention to preventing and curing the agriculture community.
North West Group Of Institutions Dhudike, Moga, India
Title: A comparative study of various surface finishing techniques for parts produced by fused deposition modelling
Time : 12:00-12:25
The objective of the present study is to experimentally reduce the surface roughness of plastic parts by four different post processing techniques such as wax coating, mass finishing, chemical treatment, and sand paper to evaluate the most suitable one. The experiments have been conducted on ABSplus material which is a most popular material for FDM machine. Surface roughness and Dimensional accuracy were selected as the output responses for the present investigation. After the surface finishing, the parts were used as patterns in investment casting process to compare the value of surface roughness and dimensional accuracy. The best method for minimum surface roughness was chemical treatment.
Islamic Azad University, Iran
Time : 13:10-13:35
Behrooz Sepehri completed his PhD at the age of 32 years in Medical Engineering- Biomechanics in Science and Research Center Branch, Islamic Azad University, Tehran, Iran. He is working as Lecturer for courses related to areas of Biomechanics, such as Introduction to Biomechanics, Biomechanics of Bone Diseases, and Artificial Organs and Limbs. He has also published some 15 papers in related areas
Orthopedic plates are currently used in bone healing process. However they cause density loss in underlying bone because of the change in natural stress patterns. The aim of this study was to evaluate a newly developed bone plate using functional graded material, FGM in term of stress pattern. In the present study, 3D finite element models of tibial bone plate with variable stiffness of a graded material and traditional bone plates made of stainless steel and Ti alloy have been developed by using the ABAQUS software. Effects on the predicted stresses at the fracture site in the presence of a distance between the plate and fractured bone were also studied. For this purpose, a 3D model of tibia was created with the exact geometry of the real bone geometry by using CT scan images of a human left leg. Results showed that the bone plate with graded material offers less stress shielding to the bone, providing a higher compressive stress at bone to induce accelerated healing in comparison with Ti alloy and stainless-steel bone plate. Results also showed that the use of non-contact plates provide a favorable mechanical environment for the following fracture healing.