In vitro experiment of the modular orthopedic plate based on Nitinol, used for human radius bone fractures.

Shape memory alloys (SMAs) and in particular Ni-Ti alloys are commonly used in bioengineering applications as they join important qualities as resistance to corrosion, biocompatibility, fatigue resistance, MR compatibility, kink resistance with two unique thermo-mechanical behaviors: the shape memory effect and the pseudoelastic effect. They allow Ni-Ti devices to undergo large mechanically induced deformations and then to recover the original shape by thermal loading or simply by mechanical unloading. Diaphyseal fractures of the radius and ulna present specific problems not encountered in the treatment of fractures of the shafts of other long bones. The adaptive modular implants based on smart materials represent a superior solution in the osteosynthesis of the fractured bones over the conventional implants known so far. To realize the model of the implant module we used SolidWorks software. The small sizes of the modules enable the surgeon to make small incisions, using surgical techniques minimally invasive, having the following advantages: reduction of soft tissues destruction; eliminating intra-operator infections; reduction of blood losses; the reduction of infection risk; the reduction of the healing time. Numerical simulations of the virtual modular implant are realized using Visual Nastran software. The stress diagrams, the displacements diagram and the strain diagram are obtained. An in vitro experiment is made, simulating the osteosynthesis of a transverse diaphyseal fracture of human radius bone. The kinematical parameters diagrams of the staple are obtained, using SIMI Motion video capture system. The experimental diagram force-displacement is obtained.

Numerical simulations of the 3D virtual model of the human hip joint, using finite element method.

In this paper, we present a three-dimensional mathematical model for a normal hip joint. The three-dimensional finite element model has been constructed based on Computer Tomograph scans of the bones. The obtained 3D model is studied using the finite element method, taking into consideration the real structure of the bone and the mechanical characteristics of cortical and spongy. The FE model of hip joint, the material properties used to simulate the behavior of the cortical and trabecular bone (of femur and coxal bone) and the cartilage, as well as the boundary conditions are presented. The distribution map of the axial and global movements on the global model and the distribution map of the axial and von Misses strain in the cartilaginous surface of the femur are presented.

Numerical simulations of human tibia osteosynthesis using modular plates based on Nitinol staples.

The shape memory alloys exhibit a number of remarkable properties, which open new possibilities in engineering and more specifically in biomedical engineering. The most important alloy used in biomedical applications is NiTi. This alloy combines the characteristics of the shape memory effect and superelasticity with excellent corrosion resistance, wear characteristics, mechanical properties and a good biocompatibility. These properties make it an ideal biological engineering material, especially in orthopedic surgery and orthodontics. In this work, modular plates for the osteosynthesis of the long bones fractures are presented. The proposed modular plates are realized from identical modules, completely interchangeable, made of titanium or stainless steel having as connecting elements U-shaped staples made of Nitinol. Using computed tomography (CT) images to provide three-dimensional geometric details and SolidWorks software package, the three dimensional virtual models of the tibia bone and of the modular plates are obtained. The finite element models of the tibia bone and of the modular plate are generated. For numerical simulation, VisualNastran software is used. Finally, displacements diagram, von Misses strain diagram, for the modular plate and for the fractured tibia and modular plate ensemble are obtained.

Properties and medical applications of shape memory alloys.

One of the most known intelligent material is nitinol, which offers many functional advantages over conventional implantable alloys. Applications of SMA to the biomedical field have been successful because of their functional qualities, enhancing both the possibility and the execution of less invasive surgeries. The biocompatibility of these alloys is one of their most important features. Different applications exploit the shape memory effect (one-way or two-way) and the super elasticity, so that they can be employed in orthopedic and cardiovascular applications, as well as in the manufacture of new surgical tools. Therefore, one can say that smart materials, especially SMA, are becoming noticeable in the biomedical field. Super elastic NiTi has become a material of strategic importance as it allows to overcome a wide range of technical and design issues relating to the miniaturization of medical devices and the increasing trend for less invasive and therefore less traumatic procedures. This paper will consider just why the main properties of shape memory alloys hold so many opportunities for medical devices and will review a selection of current applications.

Modular adaptive bone plate for humerus bone osteosynthesis.

The present paper describes a bionics application of shape memory alloy in construction of orthopedic implant. The main idea of this paper is related to design modular adaptive implants for fractured bones. In order to target the efficiency of medical treatment, the implant has to protect the fractured bone, for the healing period, undertaking much as is possible from the daily usual load of the healthy bones. The adaptability of this design is related to medical possibility of the doctor to made the implant to correspond to patient specifically anatomy. Using a CT-realistic numerical humerus bone model, the mechanical simulation of the osteosyntesis process for humerus bone using staples made out of Nitinol. The stress and displacements diagrams for bone, for plate modules and for staples, are presented.

Modular adaptive implant based on smart materials.

Applications of biological methods and systems found in nature to the study and design of engineering systems and modern technology are defined as Bionics. The present paper describes a bionics application of shape memory alloy in construction of orthopedic implant. The main idea of this paper is related to design modular adaptive implants for fractured bones. In order to target the efficiency of medical treatment, the implant has to protect the fractured bone, for the healing period, undertaking much as is possible from the daily usual load of the healthy bones. After a particular stage of healing period is passed, using implant modularity, the load is gradually transferred to bone, assuring in this manner a gradually recover of bone function. The adaptability of this design is related to medical possibility of the physician to made the implant to correspond to patient specifically anatomy. Using a CT realistic numerical bone models, the mechanical simulation of different types of loading of the fractured bones treated with conventional method are presented. The results are commented and conclusions are formulated.

CAD method for three-dimensional model of the tibia bone and study of stresses using the finite element method.

In the real life, the leg and its skeleton are exposed at the most diverse stresses. It is known that the human bone is one of the most important natural composite materials. The paper presents a method of study and the steps to obtain the virtual bones of the human body, method applied to tibia bone. For that purpose was used a CAD parametric software which permits to define models with a high level of complexity. To obtain the bone cross sections of the tibia bone a Computer Tomograph was used. The obtained 3D model is studied using the finite element method, taking into consideration the real structure of the bone and the mechanical characteristics of cortical and spongy, and we can obtain the stresses distribution for different solicitation.

The virtual model of the prosthetic tibial components.

The paper presents a method of study and the steps to obtain the virtual tibial component of the human knee joint prosthesis. For that purpose CAD parametric software was used which allows the construction of a high definition model. The obtained 3D model was studied using the finite element method and the stress and displacements distribution was obtained for different solicitations of the prosthetic and non-prosthetic tibial component of the virtual knee joint.

The generation of the three-dimensional model of the human knee joint.

In this paper we analyze the anatomic elements that compose the human knee joint. Also, we build the spatial model of the human knee joint components. This study is necessary for the design of prosthesis elements and for the establishment of the necessary prosthesis technique.

Analysis of stress and displacements of phalanx bone with the finite element method.

In this paper analyze of phalanx bone supposed at compression, torsion and bending is made. We know that the bones are one of the most important natural composite materials. The finite element method offers the possibility for the study of the stress and the displacements which appears in different solicitations cases. We realized that the most solicited parts of the bone which will be the next broken parts, so the fracture are the once from the meeting of the bone's body with its hand. The observations made by studying 74 cases of fractures caused by torsion and compression and also made by the testing of 23 phalanx bones confirm these conclusions.

Histological study [correction of styudy] of the femural head and neck microscopic architecture in persons with senile osteoporosis.

For our study were available fragments of bony tissue from 24 patients (15 females and 9 males) aged between 55-82 which needed hip arthroplasty after they had undergone femural neck fractures. Biologic pieces have been fixed, then decalcified and processed by wax embedding. We noted that the spongious osseous tissue appeared as rarefied after the remoulding processes; osseous traveas grew unplainly thinner, with their large areolar cavities filled of bony yellow marrow. The osseous cortex presented deformed osteomas with large irregular Havers ducts. The osteocytes appeared rarefied, of small size with a picnotic and hyperchrome nucleus.

Experimental measurement of flexion-extension movement in normal and osteoarthritic human knee.

The paper presents a comparative experimental study of flexion-extension movement in normal and osteoarthritic human knee. Measurements were performed on a group of seven healthy subjects and on a group of five patients with OA knees, for which experimental data were acquired for walking cycles on treadmill. Using an electrogoniometer-based acquisition system, the data were collected during the experimental gait on a treadmill with the speed equal to 3.6 km/h. The flexion angle during the gait cycle revealed differences with respect to flexion magnitude between the OA patients and the healthy subjects group. Statistical analysis demonstrated that the knee flexion angles were significantly different for experimental measurements of the OA patients' knees and healthy knees, but, also, the healthy knees of the patients were on average less flexed than gait cycle of the healthy subjects.