Sharif Digital Repository

Spine column is the most important musculoskeletal structures. One of the serious health problems in societies, especially among aged population is osteoporosis. Loss of bone density in bone structures is called osteoporosis which increases the risk of fracture due to a decrease of bone stiffness and bone strength. Spine is the most common sites for osteoporosis-related fractures. Current assessment of osteoporosis status is based on bone densitometry tools like QCT (Quantitative Computed Tomography) or DEXA (Dual Energy X-ray absorptiometry). With these methods it is only possible to estimate density without any consideration the morphology of trabecular making parts like rods and plates.... 

Fractures of the shaft of the long bones-especially in femur and tibia- is one of the most common fractures. In past decades various methods have been suggested for induction, fixation and repair of these fractures. The main fixation method for shaft fractures of femur and tibia in adult patients is named “Intramedullary Nailing”. In this method, after inducing the fracture, the bone marrow is pulled out via a hole created in the proximal part of the bone. Then, a nail will go down through this empty space inside the bone. This nail will be fixed in to proximal and distal parts of fractures with some locking screws. This way, the part of fracture cannot move respect to each other and the... 

The goal of fracture reduction in orthopedic surgery is to reposition the bone fragments in their anatomical orientation (alignment), and the fracture ends closed to each other (apposition). Reduction of long bone fractures is became an interesting subject in the field of robotic aided surgery in pervious decade. Nowadays reduction of femur is carried out by surgeons and medical staff in surgery. Due to the large holding forces necessary, exact positioning is difficult and time consuming. What is needed is an automated system whereby the fractured ends of the bone may be precisely positioned without the need for multiple docking attempts. The fragments need to be held in place as long as... 

Bones adapt their form and structure to make an efficient use of their mass against the applied mechanical loads. So, it is not surprising to assume that the geometry and density distribution of a bone contains information about its loading history. The objective of this work was to develop a framework to simulate the bone remodeling procedure as a topology optimization process and then use this framework to develop a simple technique for estimating the dominant joint loads based on the bone’s density distribution.
At first, the remodeling equation was derived from the structural optimization task of minimizing the strain energy in each time step, using the level set method. Employment... 

Implant primary stability is a crucial component of implant survival. Primary mechanical stability is correlated with implant type, surgical technique, quantity and quality of bone at the recipient site. Since bone integration (BI) significance has been acknowledged, a variety of techniques have been developed to quicken BI and achieve faster fixation. Studies have shown that material type, and many surface properties, including as surface composition, roughness, topography, and energy, have a significant influence during the early stages of bone integration to the implant. In this work, we did synthesis one-dimensional nanoneedle-like arrays of hydroxyapatite using the injection method... 

In the last decade, mechanical metamaterials have attracted more attention due to new design principles that combine the concept of hierarchical architecture with material size effects at the micro or nano scale. This strategy shows extraordinary mechanical performance that we use in unknown parts of the material property space, including strength-to-density ratios, extraordinary flexibility, and the ability to absorb energy with brittle components. The aim of this research was to print metamaterial scaffolds from a combination of biocompatible and bioactive to be used as scaffolds in bone tissue engineering. In addition to the biological properties appropriate to the host tissue, the... 

Bone scaffolds are used to regenerate bone tissue and accelerate bone healing, for this purpose, an attempt was made to prepare biocompatible, biodegradable, low toxicity and non-allergenic scaffolds to help increase osteogenesis and improve bone infections. A porous multi-component composite of chitosan, hydroxyapatite, graphene oxide functionalized with silver was made to make the desired scaffolds. At first, graphene oxide was functionalized by silver ions using silver nitrate. The structure of silver graphene oxide nanocomposite was confirmed by scanning electron microscope (SEM), Fourier infrared spectroscopy (FT-IR), and ultraviolet (UV-Visible) spectroscopy. In the next step, a... 

In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg)... 

Hydroxyapatite is the most substantial inorganic component of bone tissue which displays great biocompability and bioactivity. Nevertheless, its mechanical properties is not appropriate for a bone substitiues. Therefore, it is used to improve the mechanical properties of polymer matrix composite scaffolds. In the present work chitosan as a polymeric matrix was employed to fabricate hydroxyapatite- chitosan biocomposite scaffolds. Sol-Gel method was employed to synthesize hydroxyapatite nano particles. Porous scaffolds were fabricated via freeze-drying by introducing two different cross linkers, Glutaraldehyde and Sodium Tripolyphosphate. Mechanical (compressive strength), biocampability and... 

With the increase in the average age of the world's population, osteoporosis is a worldwide incidence. This disease, along with natural disasters, are important factors in the occurrence of fractures in various bones of the body. One of the methods for solving this problem and replacing with broken body bones is the use of metal implants with hydroxyapatite-based coatings. One of the common problems with using implants in the body is the infection in the adjacent parts of the implant. To overcome this problem, several studies have been carried out on the use of hydroxyapatite coatings with metal ions or antibacterial oxide compounds. In the present study, the influence of factors such as the... 

Tissue regeneration by bio-compatible/degradable scaffolds is one of the widely used approaches in the field of tissue engineering. In this study, a thermoplastic starch based nanocomposite scaffold with gradient structure was fabricated by unidirectional freeze drying method. To increase the stability of the scaffold in the aqueous media, PVA was added to starch solution. Then, the PVA and starch molecules were cross-linked by adding citric acid to the mixture. On the one hand, to improve the mechanical properties of the scaffold, and control its bio-degradability on the other, cellulose nano-fibers were employed. Also, the bioactivity of the scaffold was induced by using hydroxyapatite... 

Hydroxyapatite is the most substantial inorganic constituent of bone tissue which displays splendid biocompability and bioactivity. Nevertheless, its mechanical properties is not utmost appropriate for a bone substitutes. Therefore, it is used to improve the mechanical properties of polymer matrix composite scaffolds. In the present work polycaprolactone as a polymeric matrix was employed to fabricate hydroxyapatite-polycaprolactone biocomposite scaffolds via in situ route. Solvothermal method was employed to synthesize in situ hydroxyapatite in polymer matrix. Porous scaffolds were fabricated via freeze-drying/porogen leaching. Physical, mechanical (compressive module and compressive... 

This project aimed to fabricate the bone scaffolds with applying thermoplastic starch-based nano-biocomposites. The starting materials for this scaffold are as follows: thermoplastic starch, ethylene vinyl alcohol as the polymer matrix and nanoforsterite as the ceramic reinforcing phase. Furthermore, vitamin E was used as antioxidant for preserving starch against thermo-mechanical degradations. Likewise, 3D pore structure was developed using azo-dicarbonamide and water in injection moulding process. With blending thermoplastic starch and ethylene vinyl alcohol, some thermoplastic starch’s properties including degradation rate and water absorption were modified. In addition, having... 

Magnesium and its alloys are potentialy biodegradable implant materials due to their attractive biological properties. But their poor corrosion resistance may result in sudden failure of the implants. Recently, many researchers have focused on applications of fluorine-doped hydroxyapatiteCa10(PO4)6(OH)2−xFx (FHA, x is the degree of fluoridation) as a bioactive coating to provide early stability and long-term performance. In comparison with pure HA coating,FHA coating could provide significant dissolution-resistant property, better apatite-like layer deposition, better protein adsorption, better cell attachment and improved alkaline phosphatase activity in cell culture. In this... 

Drug-eluting bone implant coatings is a new era that has gained a lot of attention in recent years. In this matter, drug is loaded in the coating and local and targeted release of the drug results in preventing the side effects of implantation and increasing the healing process of the patient. The aim of this project was to synthesis the antibiotic eluting chitosan-based composite using electrophoretic deposition for bone implant coating. By using electrophoretic deposition chitosan and chitosan-bioglass composite coatings were synthesized. Then the probability of loading of drug into coating by using electrophoretic deposition was evaluated and by using this process chitosan and... 

Development of new engineered materials for bone tissue engineering applications is rapidly growing. The most important characteristics of materials, which can be used for bone tissue engineering applications, are appropriate mechanical properties, degradation rate, swelling behavior, and bioactivity. The goal of the current investigation is to study the feasibility of incorporating a modified nano-biocomposite based on biodegradable thermoplastic starch for bone tissue engineering. Nano particles of ?-tricalcium phosphate and hydroxyapatite were incorporated for reinforcing the matrix as well as improving the bioactivity. A second biodegradable polymer, i.e. polycaprolactone, was used... 

Interconnected–pore titanium scaffolds were fabricated by sintering of compressed mixture of TiH1.924 and urea or NaCl. Urea was removed by evaporation during sintering and NaCl was removed with water. TiH1.924 was used to enhance gas evolution for perpetuation of foam formation. Morphological studies of the spacer-removed scaffolds showed that the spacer shapes were replicated to the pores. Minimization of stress concentration at walls of the pores was, hence, helped by utilization of the spacers with spherical particles. The scaffolds having relative densities of 0.34 to 0.65 consisted pores of 200 to 600 μm diameter, compression strengths of 51 to 260 MPa, Young’s modulus of 6.3 to 22.66... 

Bone scaffolds are combinations of several materials, for achieving suitable properties and usage for replacing with defected bone. In this study, TCP/Agarose scaffolds are fabricated by two different approaches. The first one is using polymer sponge and gel casting technique and the other one is using foaming agent in order to obtain scaffolds with same porosity. The results show that in spite of same structure and porosity, scaffolds have different mechanical properties due to their different morphologies. Compressive strength of the scaffolds which were fabricated using polymer sponge method is 2.25MPa and elastic modulus is 56.8MPa. After coating with Agarose, compressive strength... 

In this research, we developed a drug release system of two biocompatible and biodegradable polymers and biocompatible ceramic nanoparticles. Hydrogels of sodium alginate (SA) were crosslinked using calcium chloride. The SA hydrogels were blended with polyvinyl pyrrolidone (PVP) and mixed with hydroxyapatite nanoparticles (HAP) to make hydrogel nanocomposites in the form of microbeads as drug carriers. Ciprofloxacin was selected as a model antibiotic drug for treatment of bone infection. It was found that SA and PVP form hydrogen bonds and are miscible at whole range of concentrations. Indeed, the SA/PVP blends may be considered as interpenetrating polymer networks (IPNs). HAP nanoparticles... 

Cranioplasty is a surgical procedure for repairing skull defects. This surgery will protect the brain tissue, reduce pain in the lesion site and reduce the psychological burden on the patient. Cranioplasty implants should have distinct characteristics, i.e., high strength for protecting the brain, full coverage of skull defects, resistance to infection, non-expansion with heat, and reasonable price. Titanium implants, bone allografts, hydroxyapatite, and methyl methacrylate are commonly used in this surgery. However, these materials have many disadvantages that limit their use. As a result, biodegradable material and 3D printing technology are the next steps for designing scaffolds according...