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At least 1,423 records · Page 79Linked to original sources
PubMed2006

[Contribution of biomechanics to anterior cruciate ligament reconstruction].

For years, bioengineers and orthopedic surgeons have applied the principles of biomechanics to gain valuable information about the complex function of the anterior cruciate ligament (ACL), as well as to improve the design of replacement grafts for ACL reconstruction. New experimental tools, such as robotic testing systems and mathematical models have been used to measure the multiple degree-of-freedom (DOF) knee kinematics, in situ forces, and biomechanical properties of the ACL. This manuscript will review specific examples of how biomechanics has impacted surgical reconstruction of the ACL by improving technical factors such as graft selection, tunnel placement, initial graft tension, graft fixation, and graft tunnel healing. Evolution of the single-bundle ACL reconstruction to the more anatomical double-bundle reconstruction will be featured. Finally, the future role of biomechanics to facilitate in vivo data for further improvement of ACL reconstruction will be discussed.

Anterior Cruciate Ligament↗
PubMed2001

Bone graft substitutes for the promotion of spinal arthrodesis.

In the prototypical method for inducing spinal fusion, autologous bone graft is harvested from the iliac crest or local bone removed during the spinal decompression. Although autologous bone remains the "gold standard" for stimulating bone repair and regeneration, modern molecular biology and bioengineering techniques have produced unique materials that have potent osteogenic activities. Recombinant human osteogenic growth factors, such as bone morphogenetic proteins, transforming growth factor-beta, and platelet-derived growth factor are now produced in highly concentrated and pure forms and have been shown to be extremely potent bone-inducing agents when delivered in vivo in rats, dogs, primates, and humans. The delivery of pluripotent mesenchymal stem cells (MSCs) to regions requiring bone formation is also compelling, and it has been shown to be successful in inducing osteogenesis in numerous preclinical studies in rats and dogs. Finally, the identification of biological and non-biological scaffolding materials is a crucial component of future bone graft substitutes, not only as a delivery vehicle for bone growth factors and MSCs but also as an osteoconductive matrix to stimulate bone deposition directly. In this paper, the currently available bone graft substitutes will be reviewed and the authors will discuss the novel therapeutic approaches that are currently being developed for use in the clinical setting.

Animals↗
PubMed2006

[Mechanism of low intensity ultrasound enhanced biological treatment of wastewater].

Low intensity ultrasonic irradiation can improve activity of microorganisms effectively, and thus it can be used to enhance the biological treatment of wastewater and increase the treatment efficiency through improving microbial activity in the biological reactor. The research achievements from home and abroad on the application of ultrasound (US) in bioengineering and biology were comprehensively summarized. The biological effect of low intensity US and the main mechanisms of biological activity enhancement were discussed, and the future application of low intensity US in biological wastewater treatment was analyzed accordingly.

Bacteria↗
PubMed2006

[Healing of skin lesions in diabetic foot syndrome during hospitalization].

Wound healing during the diabetic foot disease is indicated to in-patient treatment in case of non-healing wound, in case of serious infection and/or critical ischemia and in case of necessity of surgical treatment. Diabetic foot disease is the main reason for in-patient treatment of people with diabetes, which our experience confirms. Chronic wound is characterised by non-healing for at least 4 weeks. Ischemia and recurrent trauma caused by incomplete off-loading, prolong inflammation and infection are the main reasons for difficult healing of chronic wound. Infection is also leading cause for prolonged hospitalisation of patients with diabetic foot disease. Local decrease of grow factors and increase of tissue protease are characteristics of chronic wound. The process of wound healing is characterized by a cascade of interrelated events involving infection and inflammatory factors. The results of these investigations led to the moist wound healing concept and use of growth factors and bioengineered skin substitutes. We have good experience with the use of xenotransplant skin substitues in the treatment of diabetic foot. Off loading techniques including total contact casting, local therapy by debridement and skin substitutes had the best evidence based efficacy. We are introducing new method of the treatment of diabetic foot--VAC--vacuum assisted closure. The fundamental principle in the therapy during in-patient period, is comprehensive approach; the omitting of any of the principle of the therapy--e.g. the off-loading of the ulcers, the infection and ischemia control, may contribute to its failure.

Diabetic Foot↗
PubMed2004

Flaw tolerant bulk and surface nanostructures of biological systems.

Bone-like biological materials have achieved superior mechanical properties through hierarchical composite structures of mineral and protein. Gecko and many insects have evolved hierarchical surface structures to achieve extraordinary adhesion capabilities. We show that the nanometer scale plays a key role in allowing these biological systems to achieve their superior properties. We suggest that the principle of flaw tolerance may have had an overarching influence on the evolution of the bulk nanostructure of bone-like materials and the surface nanostructure of gecko-like animal species. We demonstrate that the nanoscale sizes allow the mineral nanoparticles in bone to achieve optimum fracture strength and the spatula nanoprotrusions in Gecko to achieve optimum adhesion strength. In both systems, strength optimization is achieved by restricting the characteristic dimension of the basic structure components to nanometer scale so that crack-like flaws do not propagate to break the desired structural link. Continuum modeling and atomistic simulations have been conducted to verify the concept of flaw tolerance at nanoscale. A simple tension-shear chain model has been developed to model the stiffness and fracture energy of biocomposites. It is found that, while the problem of low toughness of mineral crystals is alleviated by restricting the crystal size to nanoscale, the problem of low modulus of protein has been solved by adopting a large aspect ratio for the mineral platelets. The fracture energy of biocomposites is found to be proportional to the effective shear strain and the effective shear stress in protein along its path of deformation to fracture. The bioengineered mineral-protein composites are ideally suited for fracture energy dissipation as the winding paths of protein domain unfolding and slipping along protein-mineral interfaces lead to very large effective strain before fracture. The usual entropic elasticity of biopolymers may involve relatively small effective stress and may not be able to ensure simultaneous domain unfolding and interface slipping. Cross-linking mechanisms such as Ca++ induced sacrificial bonds in bone can increase the shear stress in protein and along the protein-mineral interface, effectively converting the behavior of entropic elasticity to one that resembles metal plasticity. The sacrificial bond mechanism not only builds up a large effective stress in protein but also allows protein deformation and interface slipping to occur simultaneously under similar stress levels, making it possible to engineer a very long range of deformation under significant stress in order to maximize energy absorption. Optimization of mineral platelets near theoretical strength is found to be crucial for allowing a large effective stress to be built up in protein via cross-linking mechanisms such as Ca++ induced sacrificial bonds. Similarly, for gecko adhesion, the strength optimization of individual spatulas is found to play a critical role in enhancing adhesion energy at the higher hierarchical level.

Biocompatible Materials↗
PubMed2006

Biometric identification using 3D face scans.

Biometrics is an emerging area of bioengineering that pursues the characterization of a person by means of something that the person is or produces. Face recognition is a particularly attractive biometric challenge. Most of the face recognition research performed in the past used 2D intensity images. However, algorithms based on 2D images are not robust to changes of illumination in the environment or orientation of the subject. The ability to acquire 3D scans of human faces removes those ambiguities, since they capture the exact geometry of the subject, invariant to illumination and orientation changes. Unencumbered by those limitations, research in 3D face recognition is now beginning to address a different source of error in biometric recognition: facial geometry deformation caused by facial expressions, which can make 3D algorithms which treat 3D faces as rigid surfaces fail. In this paper, a 3D face recognition framework is proposed to tackle this problem. The framework is composed of three subsystems: expression recognition system, expressional face recognition system and neutral face recognition system. In particular, a system for the recognition of faces with one type of expression (smile) and neutral faces was implemented and tested on a database of 30 subjects. The results proved the feasibility of this framework.

Algorithms↗
PubMed2006

Emotion-affected decision making in human simulation.

Human modelling is an interdisciplinary research field. The topic, emotion-affected decision making, was originally a cognitive psychology issue, but is now recognized as an important research direction for both computer science and biomedical modelling. The main aim of this paper is to attempt to bridge the gap between psychology and bioengineering in emotion-affected decision making. The work is based on Ortony's theory of emotions and bounded rationality theory, and attempts to connect the emotion process with decision making. A computational emotion model is proposed, and the initial framework of this model in virtual human simulation within the platform of Virtools is presented.

Artificial Intelligence↗
PubMedDate not supplied

The importance of the elastic and plastic components of strain in tensile and compressive fatigue of human cortical bone in relation to orthopaedic biomechanics.

The longevity, success, or failure of an orthopaedic implant is dependent on its osseointegration especially within the initial six months of the initial surgery. The development of strains plays a crucial role in both bone modelling and remodelling. For remodelling, in particular, strains of substantial values are required to activate the osteoblastic and osteoclastic activity for the osseointegration of the implant. Bone, however, is subject to "damage" when strain levels exceed a certain threshold level. Damage is manifested in the form of microcracks; it is linked to increased elastic strain amplitudes and is accompanied by the development of "plastic" (irrecoverable, residual) strains. Such strains increase the likelihood for the implant to subside or loosen. The present study examines the rates (per cycle) by which these two components of strain (elastic and "plastic") develop during fatigue cycling in two loading modes, tension and compression. The results of this study show that these strain rates depend on the applied stress in both loading modes. It also shows that elastic and plastic strain rates can be linked to each other through simple power law relationships so that one can calculate or predict the latter from the former and vice versa. We anticipate that such basic bone biomechanics data would be of great benefit to both clinicians and bioengineers working in the field of FEA modelling applications and orthopaedic implant surgery.

Aged↗
PubMed2006

[Application of cell technologies to tissue defect closure in oncology].

In vivo and in vitro experiments on the application of cell technologies to tissue defect closure were conducted; autologic mesenchymal stem cells on 3-demensional matrices were used. The authors analyze the results of the application of bioengineering tissue equivalents for the closure of soft tissue and upper airway defects after extensive resections performed in 52 oncological patients. Tissue equivalents with stem cells provide engraftment and long-term graft functioning; they also modify wound surface, thus stimulating wound epithelization. In this study the application of tissue equivalents led to wound healing and functional recovery in 87% of patients.

Follow-Up Studies↗
PubMed2006

Platelet-rich plasma combined with skin substitute for chronic wound healing: a case report.

Contemporary management of chronic wounds focuses on improving natural healing and individualization of treatment. Incorporating multiple therapies has become increasingly common. Of interest are autologous growth factors, which are especially important in chronic wound healing and may contribute to tissue formation and epithelialization. Autologous platelet concentrate or platelet-rich plasma (PRP) is a concentration of at least five autologous growth factors and has been shown to accelerate wound healing and may have infection-fighting properties. Chronic wound healing is complicated by both decreased growth factor availability and infection, making PRP use valuable in these types of wounds. In this report, the use of PRP therapy alone and in combination with a bioengineered skin substitute as a platelet-rich tissue graft in a chronic, non-healing wound is detailed. Over 27 weeks, the patient received multiple therapies in attempts to heal a severe decubitus ulcer of the sacrum. The introduction of PRP therapy at Week 14 led to a 26% reduction in wound depth over 4 weeks. At Week 19, PRP therapy was combined with a powdered skin substitute to create a platelet-rich tissue graft. The combination brought dramatic results, eliminating wound tunneling and reducing the wound dimensions from 6.2 cm long x 6.7 cm wide x 2.7 cm deep to 5.0 cm long x 6.0 cm wide x 1.4 cm deep. The promising observations from this case report indicate that further study on the combining of PRP therapy and skin substitutes is necessary.

Humans↗
PubMed2006

Biophysics and clinical practice for regenerative processes in cirrhosis of the liver/of liver cirrhosis assisted by Delta-S Entropy Variation Systems.

AIM: The therapy in question uses an innovative bioengineering device denoted as ''Delta-S DVD Entropy Variation System''. Previous research indicated regression of cirrhosis as evaluated in its morphofunctional and symptomatological aspects. The aim of the study is to confirm and extend previous experimental observations by enhancing hemodynamic evaluation techniques. In order to clarify scar regression, it was decided to include in the endpoints a quantitative evaluation of portal hypertension called HVPG, which is sensitive to the breakdown of hepatic architecture and the influence of regeneration nodules and therefore the advance of cirrhosis. METHODS: The experimental design consists of a self-controlled study carried out on Child A-B cirrhosis patients with portal hypertension (hepatic venous pressure gradient, HVPG > or = 10 mmHg). Five patients were enrolled, 4 HCV positive, one with autoimmune cirrhosis, all showing extensive symptoms. RESULTS: At the end of the treatment all patients showed a reduction in portal hypertension (mean reduction HVPG = 40.2%, P<0.011), together with an improved ultrasound flowmeter pattern and a sharp decrease or disappearance of the symptoms. No adverse effects were reported. Efficacy on autoimmune cirrhosis was unaffected. CONCLUSIONS: By means of a quantitative analysis of portal hypertension and of functional aspects, this study confirms that the Delta-S DVD system can lead to the regression of the scar component of cirrhosis, promote the regeneration of functioning liver tissue with positive effects on hepatic functionality and prevent symptoms and the risk of varicose vein rupture.

Aged↗
PubMed2006

Improved wound healing of cutaneous sulfur mustard injuries in a weanling pig model.

OBJECTIVE: The objective was to examine the efficacy of several treatment regimens in improving wound healing of cutaneous sulfur mustard (HD) injuries. METHODS: Wound healing studies were conducted in weanling pigs. Superficial dermal HD injuries were debrided at 48 hours postexposure using an erbium-doped yttrium aluminum garnet (Er:YAG) laser, followed by application of a treatment adjunct. A variety of noninvasive bioengineering methods were conducted during the postsurgical observation period to examine the various cosmetic and functional aspects of the skin. Histopathology was performed at the end of each study (14 or 21 days postsurgery). RESULTS: As noted clinically, reepithelialization was nearly complete by 7 days postsurgery for many of the sites treated with petrolatum and scarlet red dressings. By 21 days, the skin elasticity of the petrolatum-dressed sites was not significantly different from that of sham-exposed skin. Upon dressing removal on postsurgery day 4, the neoepidermis of allograft- and thin film-dressed sites was partially removed, with resultant petechial hemorrhaging. Mean pathology scores for hydrocolloid-dressed sites were significantly lower than those of untreated HD-exposed sites on postsurgery day 14. CONCLUSIONS: Care must be taken during bandage changes, and a nonadherent dressing that could be left in place for a longer period of time (eg, 7 days) would be beneficial. The use of cultured epithelial allograft material may have a potential role if grown on a completely nonadherent backing and left undisturbed for at least a week. Xeroform Petrolatum and Scarlet Red Ointment dressings are effective and inexpensive treatment adjuncts for HD injuries.

Journal Article↗
PubMed1991

A paradigm for the next millennium: health information science.

Although historically a major concern of both the artist and the scientist was the observation of nature, the two disciplines split when science became more wedded to mathematics and quantification. Today, with visualization, art and science can again together provide a view of the natural world. A prototype curriculum for a new multidisciplinary science--Health Information Science--incorporates aspects of computer science, cognitive psychology, bioengineering, biomedical visualization, medicine, dentistry, anthropology, mathematics, library science, and the visual arts.

Art↗
PubMed1991

[Current developments in hydraulic penis prostheses].

The disappointing long-term results of alternative treatments for erectile dysfunction have led to increasing interest in penile implants. Against this backdrop, the development of reliable penile prostheses which offer easy implantation and excellent function is a challenge to bioengineers and urologists with a special interest in the treatment of erectile dysfunction.

Erectile Dysfunction↗
PubMed1990

[Circulatory assist device in counterpulsation].

PURPOSE: To test a circulatory assist device (CAD) developed in the University of São Paulo. Heart Institute, Bioengineering Division. It is a valveless chamber working through the counterpulsation principle, aiming at assistance to temporary the left ventricle. PATIENTS AND METHODS: The CAD consists of a rigid polycarbonate shell, which houses in its interior a polyurethane bag with a maximum volume of 110 cm3, driven alternately by pressure and vacuum from an external electropneumatic device synchronized with the ECG. The device worked for 300 hours in a test bench simulating the cardiovascular system in order to verify its resistance to wear and fatigue. The CAD was implanted near the aortic root of five dogs, in whom cardiac failure was induced through the use of propranolol and plasma expanders. The CAD was driven for five periods of 2 minutes separated by pauses of equal duration. The hemodynamic parameters were measured during the mentioned periods. RESULTS: "In vitro" testing resulted in no wear or fatigue. No leakage was observed. In the "in vivo" testing the averages obtained during the on and off periods of the device showed for the on periods; a) lowering of the systolic pressures of both the aorta (17.5%) and the left ventricle (LV) 15.1%), lowering of the final diastolic pressure of the LV (15.4%) and lowering of the diastolic pressure of the aorta (27.4%); b) increase in cardiac output (45.5%); c) increase of the endocardial viability ratio by 37.5%. CONCLUSION: The tested device represents a therapeutic option in cases of acute left ventricle failure, since with it an improved cardiac performance was measured and an increased coronary perfusion can be presumed.

Animals↗
PubMed1990

[Imaging diagnosis of cancer by echography].

Clinical echography has been widely used for the past 10 years in the diagnosis of various neoplastic diseases. Recent advances in high bioengineering-technology brought us many fruitful results in the field of imaging diagnosis such as x-ray computed tomography, microwave-imaging, positron CT, magnetic resonance imaging (MRI), and ultrasonography so on in this late century. Especially, ultrasonography has achieved many successes in the vast fields of medicine, many organs of soft-tissue nature, as non-invasive approach and the merit of no physical hazard of irradiation effect. Furthermore, it is capable of visualizing cancer lesions in the living human body. This lecture describes the present status of ultrasonography in the diagnosis of neoplastic diseases, especially laying emphasis on the diagnosis of abdominal disease and breast tumors.

Breast Neoplasms↗
PubMed1990

[Hydroxyapatite coated dental implants. Biological criteria and prosthetic possibilities].

Incorporating contemporary implant research and the most advanced principals of biomaterials and bioengineering puts HA-coated implant system into clinical practice. This system utilizes a streamline precision two-stage procedure similar to the swedish method and other osseointegrated systems to ensure complete fixation and an unloaded healing phase prior to the functional use of implants. The surgical concept has been theoretically improved upon by enhancing the titanium cylinders with a HA coating of 50 to 65 microns to the body. The advantages of HA have been extensively discussed. Research has shown that a biochemical reaction occurs between HA and bone and the interface between bone and ceramic is stronger than either the ceramic or bone alone. Bone adapts well to all biocompatible metals and bone will "chemically" bond to HA. An activated sintering process has been developed that enables HA to be chemically bound to the titanium cylinder using a modification of the plasma flame spray technology. This HA coating has been developed to meet the most rigorous biomechanical requirements for bonding in high stress applications of orthopedics as well as intraoral use. Biointegration is defined as "mechanochemical" clinically significant interface that predictably develops between vital load bearing bone and a bioactive calcium-phosphate ceramic metal such as HA. The design and planning of the HA-coated metal system also provides a variety of restorative choices and have been extensively discussed in this article. Clinical reports appear excellent, and the current implant system is into its fifth year of clinical use. The use of HA-coated implants has very well satisfied restorative needs as well as following sound biologic principle.

Adult↗
PubMed1990

Medicine in the twenty-fourth century.

This paper discusses one vision of medicine's future as penned by a noted current writer of science fiction. Medical progress is seen as an outgrowth of the overall advancement of human technology, especially as a result of routine exploration of deep space. Much of 24th century medicine is to be based on the merging of bioengineering with the classical medical arts. A great deal more will be known about the human animal then than now, so more healing can be done. In spite of numerous items of medical gadgetry at his disposal, the physician of 400 years hence will remain sympathetic and caring.

Forecasting↗