The Experts below are selected from a list of 405 Experts worldwide ranked by ideXlab platform
Hong Daeho - One of the best experts on this subject based on the ideXlab platform.
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Fundamental Study of the Design and Development of Magnesium-Zinc Based Alloys for Biodegradable Implant Devices
2016Co-Authors: Hong DaehoAbstract:Inert but biocompatible metals and biodegradable polymers are currently used as Orthopedic Fixations Devices to achieve bone healing. However, the high stiffness of permanent metals such as stainless steel (SS), cobalt-chromium (Co-Cr), and titanium (Ti) alloys can cause stress shielding and loosening of the surrounding bone. Long term use of these Devices can also result in wear related debris and associated risks of metallosis requiring secondary removal surgeries causing further complications. Inferior strength and acidic degradation products of biodegradable polymers on the other hand, also limit their use as Orthopedic Devices. Recently, biodegradable magnesium (Mg) and Mg-based alloys have received wide attention and have become the target of intense research due to the benefit of degradability, suitable mechanical properties matching natural bone and the desired biocompatibility. The degradation mechanism of biodegradable magnesium is primarily corrosion which tends to be highly rapid for pure Mg and most Mg based alloys resulting in rapid evolution of unwanted hydrogen gas pockets. Hence, controlling the corrosion of magnesium has been the key challenge limiting the technological development, thwarting the accelerated progress of implementation of Mg based alloys for various biomedical applications. Rapid corrosion of magnesium in the body and the associated hydrogen gas evolution results in Device failure, and consequent risks of pain and potential infection. Alteration of alloy composition and the associated microstructure has been typically employed to improve the corrosion resistance and achieve the desired mechanical properties while maintaining the essential biocompatibility suitable for a desired biomedical application. In this work, Mg-Zn based alloys were developed for biodegradable Orthopedic Fixation Device applications. Magnesium-zinc alloys have the advantage of using zinc as a major alloying element that is considered biocompatible up to a daily dose of 11 mg. Mg-Zn-Zr was thus selected as the alloy system that was accordingly processed systematically varying the elemental composition, and characterizing the resultant system for phase, structure, microstructure, in-vitro corrosion and cytocompatibility properties yielding promising preliminary results. Results of characterization showed that the processing related Mg-Zn intermetallic precipitates formed at the grain boundaries acting as initiation centers for corrosion leading to reduction in the corrosion resistance. Thus, strontium and cerium were selected and added as micro alloying elements to improve the corrosion resistance due to alteration of the alloy phase dynamics and thermodynamic stability of the precipitates. In addition, the osteogenic attributes of Mg, Sr, and Ce ions were studied using human mesenchymal stem cells. Furthermore, to demonstrate the biosafety of Mg-Zn alloys, Mg-Zn-Sr-Zr pins were implanted in a rat femoral fracture model. The model was selectively designed to result in extreme stress on the machined Mg-Zn pin hardware and also test their biocompatibility under load-bearing conditions. As intended, higher degradation rates and Device failures were observed in the micro-computed tomography (micro-CT) images. Despite the pre-designed extreme stress assisted corrosion observed, normal fracture healing response was still exhibited in the micro-CT images and bone histology demonstrating the efficacy of the alloy system. Moreover, no systemic or local tissue toxicity were detected from blood, liver and kidney assessments further validating the beneficial aspects of this alloys system for Orthopedic applications
Cipriano, Aaron Franco - One of the best experts on this subject based on the ideXlab platform.
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Development and Optimization of Magnesium Alloys and Oxide Surface Treatments for Orthopedic Implant Applications
eScholarship University of California, 2016Co-Authors: Cipriano, Aaron FrancoAbstract:The potential of Magnesium (Mg)-based temporary biodegradable metallic implants relies most heavily on the mechanical and electrochemical properties of Mg, as well as on the fact that the human body contains a large amount of Mg ions and can effectively metabolize the degradation products of Mg. To realize the benefits of Mg for Orthopedic Fixation Device applications, however, it is critical to engineer the rate of Mg degradation in the body based on end-goal design specifications. Firstly, we developed and studied Mg-xZn-0.5Ca alloys, Mg-4Zn-xSr alloys, and anodically oxidized surface treatments, all of which present innovative strategies to engineer the corrosion rates, mechanical properties, and/or improve cell-biomaterial interactions to meet clinical requirements. Secondly, we developed and implemented physiologically relevant in vitro models to evaluate cellular responses at the cell-biomaterial interface between various mammalian cell types and Mg-based biomaterials. Optimization of the methods allowed us to identify key aspects that influence Mg degradation in vitro and cellular responses to concomitant degradation products, thereby providing more comprehensive in vitro method for examining and screening bioresorbable materials compared with current standards. Lastly, we evaluated for the first time the in vivo degradation and host-response to Mg-4Zn-1Sr alloys, not only to evaluate and optimize performance of our novel materials, but also to identify factors that affect degradation and bridge the existing gap between in vitro and in vivo measurements of Mg-based biomaterials. Collectively, the results and conclusions of this dissertation supported the promising potential of bioresorbable Mg-based biomaterials for musculoskeletal implant applications. It is likely that the solution that enables clinical translation of Mg-based biomaterials will be a combination of biomedical-designed alloys and surface treatments/coatings. Furthermore, this dissertation provided design guidelines and in vitro tools to screen and optimize: alloy composition, degradation rates, cytocompatibility, and cellular responses at the cell-biomaterial interface to fine tune Mg-based biomaterials for specific implant applications
Rastogi Shishir - One of the best experts on this subject based on the ideXlab platform.
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Role of locking plates in treatment of difficult ununited fractures: a clinical study
Elsevier, 2013Co-Authors: Kumar Ashok, Gupta Himanshu, Yadav Chandra Shekhar, Khan Shah Alam, Rastogi ShishirAbstract:【Abstract】Objective: To present our experience in treatment of difficult ununited long bone fractures with locking plate. Methods: Retrospective evaluation of locking plate Fixation in 10 difficult nonunions of long bone fractures was done. Fixation was done with locking plate for femoral shaft fracture (3 patients), supracondylar fracture of femur (gap nonunion), fracture of clavicle, fracture of both forearm bones (radius and ulna) fracture of ulna, fracture of shaft of humerus, fracture of tibial diaphysis and supracondylar frac-ture of humerus (one patient each). Five fractures had more than one previous failed internal Fixation. One patient had infected nonunion which was managed by debridement with cast immobilization followed by Fixation with locking plate at six weeks. Seven fractures were atrophic, two were oligotrophic, and one was hypertrophic. Fibular autograft was used in 2 cases and iliac crest cancellous bone graft used in all the patients. Results: Minimum follow-up was 6 months (range, 6 months to 2.5 years). Average time for union was 3.4 months (range 2.5 to 6 months). None of the patients had plate-related complications or postoperative wound infections. Conclusion: Along with achieving stability with lock-ing compression plate, meticulous soft tissue dissection, acceptable reduction, good Fixation technique and bone grafting can help achieve union in difficult nonunion cases. Though locking plate does not by itself ensure bony union, we have found it to be another useful addition to our arma-mentarium for treating difficult fracture nonunions. Key words: Fractures, bone; Fractures, ununited; Bone plates; Orthopedic Fixation Device
Kumar Ashok - One of the best experts on this subject based on the ideXlab platform.
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Role of locking plates in treatment of difficult ununited fractures: a clinical study
Elsevier, 2013Co-Authors: Kumar Ashok, Gupta Himanshu, Yadav Chandra Shekhar, Khan Shah Alam, Rastogi ShishirAbstract:【Abstract】Objective: To present our experience in treatment of difficult ununited long bone fractures with locking plate. Methods: Retrospective evaluation of locking plate Fixation in 10 difficult nonunions of long bone fractures was done. Fixation was done with locking plate for femoral shaft fracture (3 patients), supracondylar fracture of femur (gap nonunion), fracture of clavicle, fracture of both forearm bones (radius and ulna) fracture of ulna, fracture of shaft of humerus, fracture of tibial diaphysis and supracondylar frac-ture of humerus (one patient each). Five fractures had more than one previous failed internal Fixation. One patient had infected nonunion which was managed by debridement with cast immobilization followed by Fixation with locking plate at six weeks. Seven fractures were atrophic, two were oligotrophic, and one was hypertrophic. Fibular autograft was used in 2 cases and iliac crest cancellous bone graft used in all the patients. Results: Minimum follow-up was 6 months (range, 6 months to 2.5 years). Average time for union was 3.4 months (range 2.5 to 6 months). None of the patients had plate-related complications or postoperative wound infections. Conclusion: Along with achieving stability with lock-ing compression plate, meticulous soft tissue dissection, acceptable reduction, good Fixation technique and bone grafting can help achieve union in difficult nonunion cases. Though locking plate does not by itself ensure bony union, we have found it to be another useful addition to our arma-mentarium for treating difficult fracture nonunions. Key words: Fractures, bone; Fractures, ununited; Bone plates; Orthopedic Fixation Device
Gupta Himanshu - One of the best experts on this subject based on the ideXlab platform.
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Role of locking plates in treatment of difficult ununited fractures: a clinical study
Elsevier, 2013Co-Authors: Kumar Ashok, Gupta Himanshu, Yadav Chandra Shekhar, Khan Shah Alam, Rastogi ShishirAbstract:【Abstract】Objective: To present our experience in treatment of difficult ununited long bone fractures with locking plate. Methods: Retrospective evaluation of locking plate Fixation in 10 difficult nonunions of long bone fractures was done. Fixation was done with locking plate for femoral shaft fracture (3 patients), supracondylar fracture of femur (gap nonunion), fracture of clavicle, fracture of both forearm bones (radius and ulna) fracture of ulna, fracture of shaft of humerus, fracture of tibial diaphysis and supracondylar frac-ture of humerus (one patient each). Five fractures had more than one previous failed internal Fixation. One patient had infected nonunion which was managed by debridement with cast immobilization followed by Fixation with locking plate at six weeks. Seven fractures were atrophic, two were oligotrophic, and one was hypertrophic. Fibular autograft was used in 2 cases and iliac crest cancellous bone graft used in all the patients. Results: Minimum follow-up was 6 months (range, 6 months to 2.5 years). Average time for union was 3.4 months (range 2.5 to 6 months). None of the patients had plate-related complications or postoperative wound infections. Conclusion: Along with achieving stability with lock-ing compression plate, meticulous soft tissue dissection, acceptable reduction, good Fixation technique and bone grafting can help achieve union in difficult nonunion cases. Though locking plate does not by itself ensure bony union, we have found it to be another useful addition to our arma-mentarium for treating difficult fracture nonunions. Key words: Fractures, bone; Fractures, ununited; Bone plates; Orthopedic Fixation Device
