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1.
Curr Med Res Opin ; 36(3): 427-437, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-31914326

RESUMEN

Objective: Meniscus deficiency is highly prevalent in the United States and represents a substantial societal cost burden. The objective of this case series was to evaluate and compare direct costs associated with treatment for acute or degenerative medial meniscus deficiency.Methods: Case series patients (n = 50) received either non-surgical therapy or an operative partial meniscectomy based on clinical assessment by the principal study investigator which included physical examination and MRI. Cumulative 24-month direct treatment costs were compared between non-surgical and operative cohorts. Direct treatment costs were calculated using billing record reimbursements for all medical services administered by the treating institution, and imputed for medical services prescribed by the treating physician but provided external to the treating institution.Results: At study initiation, 33 patients (67%) were treated with non-surgical care, and 17 patients (33%) received a partial medial meniscectomy. By 24 months, average direct treatment costs were highest for patients who received a partial medial meniscectomy at study initiation ($4488 ± $1265) compared to patients who received non-surgical care at study initiation ($4092 ± $7466), although differences in average direct treatment costs were not statistically significant across treatment cohorts (p = .830). Average direct treatment costs were highest for the subgroup of patients who initiated non-surgical therapy but received a subsequent total knee arthroplasty during the study period (n = 2; $32,197 ± $169).Conclusion: Findings from this case series suggests that patients with acute or degenerative meniscus deficiency incur substantial direct treatment costs related to their knee pathology, particularly for patients receiving total knee arthroplasty.


Asunto(s)
Meniscectomía/métodos , Meniscos Tibiales/patología , Lesiones de Menisco Tibial/terapia , Adulto , Anciano , Artroplastia de Reemplazo de Rodilla/estadística & datos numéricos , Femenino , Costos de la Atención en Salud , Humanos , Articulación de la Rodilla/patología , Masculino , Meniscectomía/economía , Meniscos Tibiales/cirugía , Persona de Mediana Edad , Estudios Prospectivos , Lesiones de Menisco Tibial/economía , Lesiones de Menisco Tibial/cirugía , Resultado del Tratamiento
2.
J Mech Behav Biomed Mater ; 49: 310-20, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-26057364

RESUMEN

A synthetic meniscus implant was recently developed for the treatment of patients with mild to moderate osteoarthritis with knee pain associated with medial joint overload. The implant is distinctively different from most orthopedic implants in its pliable construction, and non-anchored design, which enables implantation through a mini-arthrotomy without disruption to the bone, cartilage, and ligaments. Due to these features, it is important to show that the material and design can withstand knee joint conditions. This study evaluated the long-term performance of this device by simulating loading for a total of 5 million gait cycles (Mc), corresponding to approximately five years of service in-vivo. All five implants remained in good condition and did not dislodge from the joint space during the simulation. Mild abrasion was detected by electron microscopy, but µ-CT scans of the implants confirmed that the damage was confined to the superficial surfaces. The average gravimetric wear rate was 14.5 mg/Mc, whereas volumetric changes in reconstructed µ-CT scans point to an average wear rate of 15.76 mm(3)/Mc (18.8 mg/Mc). Particles isolated from the lubricant had average diameter of 15 µm. The wear performance of this polycarbonate-urethane meniscus implant concept under ISO-14243 loading conditions is encouraging.


Asunto(s)
Ensayo de Materiales , Fenómenos Mecánicos , Meniscos Tibiales , Prótesis e Implantes , Microtomografía por Rayos X , Gravitación , Cemento de Policarboxilato , Diseño de Prótesis , Propiedades de Superficie , Uretano
3.
Clin Biomech (Bristol, Avon) ; 29(8): 898-905, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-25238685

RESUMEN

BACKGROUND: In this pilot study we wanted to evaluate the kinematics of a knee implanted with an artificial polycarbonate-urethane meniscus device, designed for medial meniscus replacement. The static kinematic behavior of the implant was compared to the natural medial meniscus of the non-operated knee. A second goal was to evaluate the motion pattern, the radial displacement and the deformation of the meniscal implant. METHODS: Three patients with a polycarbonate-urethane implant were included in this prospective study. An open-MRI was used to track the location of the implant during static weight-bearing conditions, within a range of motion of 0° to 120° knee flexion. Knee kinematics were evaluated by measuring the tibiofemoral contact points and femoral roll-back. Meniscus measurements (both natural and artificial) included anterior-posterior meniscal movement, radial displacement, and meniscal height. FINDINGS: No difference (P>0.05) was demonstrated in femoral roll-back and tibiofemoral contact points during knee flexion between the implanted and the non-operated knees. Meniscal measurements showed no significant difference in radial displacement and meniscal height (P>0.05) at all flexion angles, in both the implanted and non-operated knees. A significant difference (P ≤ 0.05) in anterior-posterior movement during flexion was observed between the two groups. INTERPRETATION: In this pilot study, the artificial polycarbonate-urethane implant, indicated for medial meniscus replacement, had no influence on femoral roll-back and tibiofemoral contact points, thus suggesting that the joint maintains its static kinematic properties after implantation. Radial displacement and meniscal height were not different, but anterior-posterior movement was slightly different between the implant and the normal meniscus.


Asunto(s)
Traumatismos de la Rodilla/cirugía , Prótesis de la Rodilla , Meniscos Tibiales/cirugía , Adulto , Fenómenos Biomecánicos , Femenino , Fémur , Humanos , Articulación de la Rodilla/cirugía , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Proyectos Piloto , Cemento de Policarboxilato/química , Estudios Prospectivos , Prótesis e Implantes , Rango del Movimiento Articular , Uretano/química , Soporte de Peso
4.
Acta Biomater ; 10(6): 2762-8, 2014 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24534719

RESUMEN

Pore size distribution (PSD) within porous biomaterials is an important microstructural feature for assessing their biocompatibility, longevity and drug release kinetics. Scanning electron microscopy (SEM) is the most common method used to obtain the PSD of soft biomaterials. The method is highly invasive and user dependent, since it requires fracturing of the sample and then considers only the small portion that the user had acquired in the image. In the current study we present a novel nuclear magnetic resonance (NMR) method as an alternative method for estimation of PSD in soft porous materials. This noninvasive 3-D diffusion NMR method considers the entire volume of the specimen and eliminates the user's need to choose a specific field of view. Moreover, NMR does not involve exposure to ionizing radiation and can potentially have preclinical and clinical uses. The method was applied on four porous 50/50 poly(dl-lactic-co-glycolic acid) bioresorbable films with different porosities, which were created using the freeze-drying of inverted emulsions technique. We show that the proposed NMR method is able to address the main limitations associated with SEM-based PSD estimations by being non-destructive, depicting the full volume of the specimens and not being dependent on the magnification factor. Upon comparison, both methods yielded a similar PSD in the smaller pore size range (1-25µm), while the NMR-based method provided additional information on the larger pores (25-50µm).


Asunto(s)
Materiales Biocompatibles , Espectroscopía de Resonancia Magnética/métodos , Microscopía Electrónica de Rastreo , Porosidad
5.
J Mech Behav Biomed Mater ; 29: 42-55, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24055793

RESUMEN

There are significant potential advantages for restoration of meniscal function using a bio-stable synthetic implant that combines long-term durability with a dependable biomechanical performance resembling that of the natural meniscus. A novel meniscus implant made of a compliant polycarbonate-urethane matrix reinforced with high modulus ultrahigh molecular weight polyethylene fibers was designed as a composite structure that mimics the structural elements of the natural medial meniscus. The overall success of such an implant is linked on its capability to replicate the stress distribution in the knee over the long-term. As this function of the device is directly dependent on its mechanical properties, changes to the material due to exposure to the joint environment and repeated loading could have non-trivial influences on the viscoelastic properties of the implant. Thus, the goal of this study was to measure and characterize the strain-rate response, as well as the viscoelastic properties of the implant as measured by creep, stress relaxation, and hysteresis after simulated use, by subjecting the implant to realistic joint loads up to 2 million cycles in a joint-like setting. The meniscus implant behaved as a non-linear viscoelastic material. The implant underwent minimal plastic deformation after 2 million fatigue loading cycles. Under low compressive loads, the implant was fairly flexible, and able to deform relatively easily (E=120-200 kPa). However as the compressive load applied on the implant was increased, the implant became stiffer (E=3.8-5.2 MPa), to resist deformation. The meniscus implant appears well-matched to the viscoelastic properties of the natural meniscus, and importantly, these properties were found to remain stable and minimally affected by potentially degradative and loading conditions associated with long-term use.


Asunto(s)
Ensayo de Materiales , Meniscos Tibiales , Prótesis e Implantes , Sustancias Viscoelásticas , Absorción , Estrés Mecánico , Soporte de Peso
6.
Biomatter ; 2(4): 239-70, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-23507890

RESUMEN

For many biomedical applications, there is need for porous implant materials. The current article focuses on a method for preparation of drug-eluting porous structures for various biomedical applications, based on freeze drying of inverted emulsions. This fabrication process enables the incorporation of any drug, to obtain an "active implant" that releases drugs to the surrounding tissue in a controlled desired manner. Examples for porous implants based on this technique are antibiotic-eluting mesh/matrix structures used for wound healing applications, antiproliferative drug-eluting composite fibers for stent applications and local cancer treatment, and protein-eluting films for tissue regeneration applications. In the current review we focus on these systems. We show that the release profiles of both types of drugs, water-soluble and water-insoluble, are affected by the emulsion's formulation parameters. The former's release profile is affected mainly through the emulsion stability and the resulting porous microstructure, whereas the latter's release mechanism occurs via water uptake and degradation of the host polymer. Hence, appropriate selection of the formulation parameters enables to obtain desired controllable release profile of any bioactive agent, water-soluble or water-insoluble, and also fit its physical properties to the application.


Asunto(s)
Sistemas de Liberación de Medicamentos , Stents Liberadores de Fármacos , Animales , Ceftazidima/administración & dosificación , Liofilización , Congelación , Humanos , Pruebas de Sensibilidad Microbiana , Microscopía Electrónica de Rastreo , Neoplasias/tratamiento farmacológico , Polímeros/química , Porosidad , Regeneración , Solubilidad , Estrés Mecánico , Resistencia a la Tracción , Factores de Tiempo , Ingeniería de Tejidos/métodos , Agua/química , Cicatrización de Heridas
7.
J Orthop Res ; 29(12): 1859-66, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-21630331

RESUMEN

Soft bearing materials that aim to reproduce the tribological function of the natural joint are gaining popularity as an alternative concept to conventional hard bearing materials in the hip and knee. However, it has not been proven so far that an elastic cushion bearing can be sufficiently durable as a long term (∼20 years) articulating joint prosthesis. The use of new bearing materials should be supported by accurate descriptions of the implant following usage and of the number, volume, and type of wear particles generated. We report on a long-term 20 million cycle (Mc) wear study of a commercial hip replacement system composed of a compliant polycarbonate-urethane (PCU) acetabular liner coupled to a cobalt-chromium alloy femoral head. The PCU liner showed excellent wear characteristics in terms of its low and steady volumetric wear rate (5.8-7.7 mm(3)/Mc) and low particle generation rate (2-3 × 10(6) particles/Mc). The latter is 5-6 orders of magnitude lower than that of highly cross-linked polyethylene and 6-8 orders of magnitude lower than that of metal-on-metal bearings. Microscopic analysis of the implants after the simulation demonstrated a low damage level to the implants' articulating surfaces. Thus, the compliant PCU bearing may provide a substantial advantage over traditional bearing materials.


Asunto(s)
Acetábulo/fisiología , Acetábulo/cirugía , Artroplastia de Reemplazo de Cadera/instrumentación , Análisis de Falla de Equipo/métodos , Prótesis de Cadera , Ensayo de Materiales/métodos , Aleaciones de Cromo , Elasticidad/fisiología , Cabeza Femoral/fisiología , Cabeza Femoral/cirugía , Humanos , Modelos Anatómicos , Cemento de Policarboxilato , Factores de Tiempo , Uretano , Soporte de Peso/fisiología
8.
Burns ; 37(5): 896-904, 2011 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-21466923

RESUMEN

Approximately 70% of all people with severe burns die from related infections despite advances in treatment regimens and the best efforts of nurses and doctors. Silver ion-eluting wound dressings are available for overcoming this problem. However, there are reports of deleterious effects of such dressings due to cellular toxicity that delays the healing process, and the dressing changes needed 1-2 times a day are uncomfortable for the patient and time consuming for the stuff. An alternative concept in wound dressing design that combines the advantages of occlusive dressings with biodegradability and intrinsic topical antibiotic treatment is described herewith. The new composite structure presented in this article is based on a polyglyconate mesh and a porous poly-(dl-lactic-co-glycolic acid) matrix loaded with gentamicin developed to provide controlled release of antibiotics for three weeks. In vivo evaluation of the dressing material in contaminated deep second degree burn wounds in guinea pigs (n=20) demonstrated its ability to accelerate epithelialization by 40% compared to an unloaded format of the material and a conventional dressing material. Wound contraction was reduced significantly, and a better quality scar tissue was formed. The current dressing material exhibits promising results, does not require frequent bandage changes, and offers a potentially valuable and economic approach to treating the life-threatening complication of burn-related infections.


Asunto(s)
Antibacterianos/farmacología , Materiales Biocompatibles/farmacología , Quemaduras/terapia , Gentamicinas/farmacología , Apósitos Oclusivos , Cicatrización de Heridas/efectos de los fármacos , Análisis de Varianza , Animales , Quemaduras/tratamiento farmacológico , Quemaduras/patología , Contractura/patología , Preparaciones de Acción Retardada/farmacología , Modelos Animales de Enfermedad , Cobayas
9.
Knee Surg Sports Traumatol Arthrosc ; 19(2): 255-63, 2011 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-20635076

RESUMEN

PURPOSE: injury or loss of the meniscus generally leads to degenerative osteoarthritic changes in the knee joint. However, few surgical options exist for meniscal replacement. The goal of this study was to examine the ability of a non-degradable, anatomically shaped artificial meniscal implant, composed of Kevlar-reinforced polycarbonate-urethane (PCU), to prevent progressive cartilage degeneration following complete meniscectomy. METHODS: the artificial meniscus was implanted in the knees of mature female sheep following total medial meniscectomy, and the animals were killed at 3- and 6-months post-surgery. Macroscopic analysis and semi-quantitative histological analysis were performed on the cartilage of the operated knee and unoperated contralateral control joint. RESULTS: the PCU implants remained well secured throughout the experimental period and showed no signs of wear or changes in structural or material properties. Histological analysis showed relatively mild cartilage degeneration that was dominated by loss of proteoglycan content and cartilage structure. However, the total osteoarthritis score did not significantly differ between the control and operated knees, and there were no differences in the severity of degenerative changes between 3 and 6 months post-surgery. CONCLUSION: current findings provide preliminary evidence for the ability of an artificial PCU meniscal implant to delay or prevent osteoarthritic changes in knee joint following complete medial meniscectomy.


Asunto(s)
Meniscos Tibiales , Osteoartritis/patología , Prótesis e Implantes , Animales , Cartílago Articular , Femenino , Miembro Posterior/patología , Miembro Posterior/cirugía , Modelos Animales , Polietileno/química , Diseño de Prótesis , Ovinos , Uretano/química
10.
J Biomech Eng ; 132(10): 101008, 2010 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-20887018

RESUMEN

Allograft or synthetic menisci have been suggested as a means to restore contact pressures following meniscectomy. However, when the natural meniscus is severely damaged/absent, the necessary size cannot be determined according to the recipient size and there is a need to estimate it from magnetic resonance imaging (MRI) of the contralateral knee or the injured knee bones. The use of the contralateral-knee for size matching is problematic due to economic and practical reasons. Hence, there are significant advantages for a sizing algorithm based only on the candidate knee geometry. The aim of this study is to characterize midrange values and variability of knee dimensions and to develop a set of mathematical relations representing knee dimensions using a minimum of imaging-based bone measurements. Tibia, femur, and meniscus measurements were taken in 118 MRI scans and used to develop a representative parametric knee model in which all dimensions are expressed using tibia plateau width. The model was verified by comparing the predicted values to direct MRI measurements for 20 additional subjects by means of the Pearson correlation and Bland and Altman (1986, "Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement," Lancet, 1, pp. 307-310) plot. Anatomical parameters in the male knee were significantly larger (∼17%) compared with corresponding female measurements. However, most relations between tibia, femur, and meniscus measurements (43/56) were not significantly different between male and female populations (p ≥ 0.05), indicating that differences between male and female joints are generally related to scaling and not shape. Dimensions predicted by the knee model were in a good agreement with dimensions measured directly from the MRI (R(2)>0.96) and the Bland and Altman plot indicated that ∼95% of data points were well within the ± 2 standard deviation lines of agreement. The model proposed in this study is advantageous in being able to describe typical knee proportions for a given tibial width and can be used to predict the dimensions of a candidate knee based on a single measurement. The anatomical/anthropometric data presented in the study can be utilized in a sizing algorithm for artificial meniscal implants or in the design of artificial meniscus prostheses.


Asunto(s)
Articulación de la Rodilla/anatomía & histología , Articulación de la Rodilla/fisiología , Meniscos Tibiales/fisiología , Meniscos Tibiales/trasplante , Modelos Anatómicos , Anciano , Fenómenos Biomecánicos , Ingeniería Biomédica , Femenino , Fémur/anatomía & histología , Humanos , Traumatismos de la Rodilla/patología , Traumatismos de la Rodilla/fisiopatología , Traumatismos de la Rodilla/cirugía , Articulación de la Rodilla/cirugía , Imagen por Resonancia Magnética , Masculino , Meniscos Tibiales/anatomía & histología , Persona de Mediana Edad , Tibia/anatomía & histología
11.
J Biomech Eng ; 132(9): 095001, 2010 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-20815651

RESUMEN

The development of a synthetic meniscal implant that does not require surgical attachment but still provides the biomechanical function necessary for joint preservation would have important advantages. We present a computational-experimental approach for the design optimization of a free-floating polycarbonate-urethane (PCU) meniscal implant. Validated 3D finite element (FE) models of the knee and PCU-based implant were analyzed under physiological loads. The model was validated by comparing calculated pressures, determined from FE analysis to tibial plateau contact pressures measured in a cadaveric knee in vitro. Several models of the implant, some including embedded reinforcement fibers, were tested. An optimal implant configuration was then selected based on the ability to restore pressure distribution in the knee, manufacturability, and long-term safety. The optimal implant design entailed a PCU meniscus embedded with circumferential reinforcement made of polyethylene fibers. This selected design can be manufactured in various sizes, without risking its integrity under joint loads. Importantly, it produces an optimal pressure distribution, similar in shape and values to that of natural meniscus. We have shown that a fiber-reinforced, free-floating PCU meniscal implant can redistribute joint loads in a similar pattern to natural meniscus, without risking the integrity of the implant materials.


Asunto(s)
Meniscos Tibiales/trasplante , Modelos Biológicos , Cemento de Policarboxilato/química , Diseño de Prótesis , Uretano/química , Anciano de 80 o más Años , Simulación por Computador , Análisis de Elementos Finitos , Humanos , Articulación de la Rodilla/fisiología , Articulación de la Rodilla/cirugía , Masculino , Polietileno/química , Presión , Investigación , Tibia/fisiología
12.
Acta Biomater ; 6(12): 4698-707, 2010 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-20633706

RESUMEN

There is growing interest in the use of compliant materials as an alternative to hard bearing materials such as polyethylene, metal and ceramics in artificial joints. Cushion form bearings based on polycarbonate-urethane (PCU) mimic the natural synovial joint more closely by promoting fluid-film lubrication. In the current study, we used a physiological simulator to evaluate the wear characteristics of a compliant PCU acetabular buffer, coupled against a cobalt-chrome femoral head. The wear rate was evaluated over 8 million cycles gravimetrically, as well as by wear particle isolation using filtration and bio-ferrography (BF). The gravimetric and BF methods showed a wear rate of 9.9-12.5mg per million cycles, whereas filtration resulted in a lower wear rate of 5.8mg per million cycles. Bio-ferrography was proven to be an effective method for the determination of wear characteristics of the PCU acetabular buffer. Specifically, it was found to be more sensitive towards the detection of wear particles compared to the conventional filtration method, and less prone to environmental fluctuations than the gravimetric method. PCU demonstrated a low particle generation rate (1-5×106 particles per million cycles), with the majority (96.6%) of wear particle mass lying above the biologically active range, 0.2-10µm. Thus, PCU offers a substantial advantage over traditional bearing materials, not only in its low wear rate, but also in its osteolytic potential.


Asunto(s)
Materiales Biocompatibles/química , Articulación de la Cadera/fisiología , Prótesis de Cadera , Ensayo de Materiales/métodos , Cemento de Policarboxilato/química , Estrés Mecánico , Uretano/química , Filtración , Microscopía Electrónica de Rastreo , Tamaño de la Partícula
13.
Handb Exp Pharmacol ; (197): 299-341, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-20217535

RESUMEN

Drug-eluting medical implants are actually active implants that induce healing effects, in addition to their regular task of support. This effect is achieved by controlled release of active pharmaceutical ingredients (API) into the surrounding tissue. In this chapter we focus on three types of drug-eluting devices: drug-eluting vascular stents, drug-eluting wound dressings and protein-eluting scaffolds for tissue regeneration, thus describing both internal and external implants. Each of these drug-eluting devices also presents an approach for solving the drug release issue. Most drug-eluting vascular stents are loaded with water-insoluble antiproliferative agents, and their diffusion from the device to the surrounding tissue is relatively slow. In contrast, most drug-eluting wound dressings are loaded with highly water-soluble antibacterial agents and the issue of fast release must therefore be addressed. Growth factor release from scaffolds for tissue regeneration offers a new approach of incorporating high-molecular-weight bioactive agents which are very sensitive to process conditions and preserve their activity during the preparation stage. The drug-eluting medical implants are described here in terms of matrix formats and polymers, incorporated drugs and their release profiles from the implants, and implant functioning. Basic elements, such as new composite core/shell fibers and structured films, can be used to build new antibiotic-eluting devices. As presented in this chapter, the effect of the processing parameters on the microstructure and the resulting drug release profiles, mechanical and physical properties, and other relevant properties, must be elucidated in order to achieve the desired properties. Newly developed implants and novel modifications of previously developed approaches have enhanced the tools available for creating clinically important biomedical applications.


Asunto(s)
Sistemas de Liberación de Medicamentos , Stents Liberadores de Fármacos , Cicatrización de Heridas/efectos de los fármacos , Animales , Antibacterianos/administración & dosificación , Vendajes , Reestenosis Coronaria/prevención & control , Humanos , Polímeros/química , Andamios del Tejido , Heridas y Lesiones/tratamiento farmacológico
14.
J Biomed Mater Res B Appl Biomater ; 93(2): 425-35, 2010 May.
Artículo en Inglés | MEDLINE | ID: mdl-20127990

RESUMEN

Wound dressings aim to restore the milieu required for skin regeneration and protect the wound from environmental threats, including penetration of bacteria. The dressings should be easy to apply and remove and maintain a moist healing environment. In this study, novel biodegradable composite wound dressings based on a polyglyconate mesh and a porous PDLGA binding matrix were developed and studied. These novel dressings were prepared by dip-coating woven meshes in inverted emulsions, followed by freeze-drying. Their investigation focused on the microstructure, mechanical and physical properties, and the release profile of the antibiotic drug ceftazidime from the binding matrix. The mechanical properties of our wound-dressing structures were found to be superior, combining relatively high tensile strength and ductility, which changed only slightly during 3 weeks of incubation in an aqueous medium. The parameters of the inverted emulsion, the organic-aqueous phase ratio, and the type of surfactant used for stabilizing the emulsion were found to affect the microstructure of the binding matrix and the resulting properties, i.e., water absorbance, water vapor transmission rate, and drug-release profile from the binding matrix. Appropriate selection of these parameters can yield composite structures that have the desired physical properties and drug release behavior. Thus, these unique structures are potentially very useful as burn and ulcer dressings.


Asunto(s)
Antibacterianos/química , Vendajes , Ceftazidima/química , Sistemas de Liberación de Medicamentos , Ensayo de Materiales , Poliglactina 910 , Antibacterianos/uso terapéutico , Quemaduras/terapia , Ceftazidima/uso terapéutico , Emulsiones , Factores de Tiempo , Úlcera/terapia
15.
J Tissue Viability ; 19(2): 54-66, 2010 May.
Artículo en Inglés | MEDLINE | ID: mdl-19962896

RESUMEN

Wound dressings aim to restore the milieu required for skin regeneration by protecting the wound from environmental threats, including penetration of bacteria, and by maintaining a moist healing environment. A wide variety of wound dressing products targeting various types of wounds and different aspects of the wound healing process are currently available on the market. Ideally, a dressing should be easy to apply and remove, and its design should meet both physical and mechanical requirements; namely water absorbance and transmission rate, handleability and strength. In this article, our novel biodegradable antibiotic-eluting wound dressings are described and the engineering aspects in the design are emphasized. These unique new wound dressings are based on a polyglyconate mesh, coated with a porous Poly(dl-lactic-co-glycolic acid) matrix. They demonstrated excellent mechanical and physical properties and desired release profiles of antibiotic drugs which enable bacterial inhibition. Hence, a new generation of wound dressings is now emerging with clear benefits. These include better protection against infection and reducing the need for frequent dressing changing.


Asunto(s)
Apósitos Oclusivos , Heridas y Lesiones/terapia , Antibacterianos/administración & dosificación , Ceftazidima/administración & dosificación , Preparaciones de Acción Retardada , Diseño de Equipo , Femenino , Humanos , Ensayo de Materiales , Fenómenos Mecánicos , Polímeros
16.
Acta Biomater ; 5(8): 2872-83, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-19416766

RESUMEN

Novel antibiotic-eluting composite fibers designed for use as basic wound dressing elements were developed and studied. These structures were composed of a polyglyconate core and a porous poly(dl-lactic-co-glycolic acid) shell loaded with one of three antibiotic drugs: mafenide acetate, gentamicin sulphate and ceftazidime pentahydrate. The shell was prepared by the freeze-drying of inverted emulsions. The fiber investigation focused on the effects of the emulsion's formulation on the shell microstructure and on the resulting profile of drug release from the fibers. Albumin was found to be the most effective surfactant for stabilizing the inverted emulsions and also to have a beneficial holdup effect on the release kinetics of the hydrophilic antibiotic drugs, especially mafenide acetate, probably through a specific interaction. An increase in the organic:aqueous phase ratio, polymer content or molecular weight of the host polymer resulted in a decrease in the burst release and a more moderate release profile due to changes in shell microstructure. The first two parameters were found to be more effective than the third. The diverse release profiles obtained in the current study and the good mechanical properties indicate that our new composite fibers have good potential for use in wound healing applications.


Asunto(s)
Antibacterianos/administración & dosificación , Antibacterianos/química , Materiales Biocompatibles/química , Portadores de Fármacos/administración & dosificación , Portadores de Fármacos/química , Pseudomonas aeruginosa/efectos de los fármacos , Staphylococcus/efectos de los fármacos , Implantes Absorbibles , Absorción , Supervivencia Celular/efectos de los fármacos , Difusión , Módulo de Elasticidad , Ensayo de Materiales , Porosidad , Propiedades de Superficie , Resistencia a la Tracción
17.
J Biomed Mater Res A ; 89(3): 654-66, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-18442118

RESUMEN

New gentamicin-eluting bioresorbable core/shell fiber structures were developed and studied. These structures were composed of a polyglyconate core and a porous poly(DL-lactic-co-glycolic acid) (PDLGA) shell loaded with the antibiotic agent gentamicin, prepared using freeze drying of inverted emulsions. These unique fibers are designed to be used as basic elements of bioresorbable burn and ulcer dressings. The investigation focused on the effects of the emulsion's composition (formulation) on the shell's microstructure, on the drug release profile from the fibers, and on bacterial inhibition. The release profiles generally exhibited an initial burst effect accompanied by a decrease in release rates with time. Albumin was found to be the most effective surfactant for stabilizing the inverted emulsions. All three formulation parameters had a significant effect on gentamicin's release profile. An increase in the polymer and organic:aqueous phase ratio or a decrease in the drug content resulted in a lower burst release and a more moderate release profile. The released gentamicin also resulted in a significant decrease in bacterial viability and practically no bacteria survived after 2 days when using bacterial concentrations of 1 x 10(7) CFU/mL. Thus, our new fiber structures are effective against the relevant bacterial strains and can be used as basic elements of bioresorbable drug-eluting wound dressings.


Asunto(s)
Materiales Biocompatibles/farmacología , Gentamicinas/farmacología , Cicatrización de Heridas/efectos de los fármacos , Bacterias/citología , Bacterias/efectos de los fármacos , Recuento de Colonia Microbiana , Sistemas de Liberación de Medicamentos , Emulsiones , Pruebas de Sensibilidad Microbiana , Viabilidad Microbiana/efectos de los fármacos , Microscopía Electrónica de Rastreo , Polímeros/química , Tensoactivos/farmacología
18.
J Biomech ; 41(16): 3322-31, 2008 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-19026415

RESUMEN

Deep tissue injury (DTI) is a severe form of pressure ulcers that occur in subcutaneous tissue under intact skin by the prolonged compression of soft tissues overlying bony prominences. Pressure ulcers and DTI in particular are common in patients with impaired motosensory capacities, such as those with a spinal cord injury (SCI). Obesity is also common among subjects with SCI, yet there are contradicting indications regarding its potential influence as a risk factor for DTI in conditions where these patients sit in a wheelchair without changing posture for prolonged times. It has been argued that high body mass may lead to a greater risk for DTI due to increase in compressive forces from the bones on overlying deep soft tissues, whereas conversely, it has been argued that the extra body fat associated with obesity may reduce the risk by providing enhanced subcutaneous cushioning that redistributes high interface pressures. No biomechanical evaluation of this situation has been reported to date. In order to elucidate whether obesity can be considered a risk factor for DTI, we developed computational finite element (FE) models of the seated buttocks with 4 degrees of obesity, quantified by body mass index (BMI) values of 25.5, 30, 35 and 40kg/m(2). We found that peak principal strains, strain energy densities (SED) and von Mises stresses in internal soft tissues (muscle, fat) overlying the ischial tuberosities (ITs) all increased with BMI. With a rise in BMI from 25.5 to 40kg/m(2), values of these parameters increased 1.5 times on average. Moreover, the FE simulations indicated that the bodyweight load transferred through the ITs has a greater effect in increasing internal tissue strains/stresses than the counteracting effect of thickening of the adipose layer which is concurrently associated with obesity. We saw that inducing some muscle atrophy (30% reduction in muscle volume, applied to the BMI=40kg/m(2) model) which is also characteristic of chronic SCI resulted in further substantial increase in all biomechanical measures reflecting geometrical distortion of muscle tissue, that is, SED, tensile stress, shear stress and von Mises stress. This result highlights that obesity and muscle atrophy, which are both typical of the chronic phase of SCI, contribute together to the state of elevated tissue loads, which consequently increases the likelihood of DTI in this population.


Asunto(s)
Tejido Adiposo/fisiopatología , Modelos Biológicos , Músculo Esquelético/fisiopatología , Obesidad/complicaciones , Obesidad/fisiopatología , Úlcera por Presión/etiología , Úlcera por Presión/fisiopatología , Traumatismos de la Médula Espinal/complicaciones , Traumatismos de la Médula Espinal/fisiopatología , Nalgas/fisiopatología , Simulación por Computador , Módulo de Elasticidad , Humanos , Presión , Medición de Riesgo/métodos , Factores de Riesgo , Estrés Mecánico
19.
J Control Release ; 130(3): 202-15, 2008 Sep 24.
Artículo en Inglés | MEDLINE | ID: mdl-18687500

RESUMEN

Infection is defined as a homeostatic imbalance between the host tissue and the presence of microorganisms. It is associated with a large variety of wound occurrences ranging from traumatic skin tears and burns to chronic ulcers and complications following surgery and device implantations. If the wound setting manages to overcome the microorganism invasion by a sufficient immune response then the wound should heal. If not, the formation of an infection can seriously limit the wound healing process. Evidence of increasing bacterial resistance is on the rise, and complications associated with infections are therefore expected to increase. The main goal in treating various types of wound infections is to decrease the bacterial load in the wound to a level that enables wound healing processes to take place. Conventional systemic delivery of antibiotics entails poor penetration into ischemic and necrotic tissue and can cause systemic toxicity with associated renal and liver complications, which result in a need for hospitalization for monitoring. Alternative local delivery of antibiotics by either topical administration or by a delivery device may enable the maintenance of a high local antibiotic concentration for an extended duration of release without exceeding systemic toxicity. The present review describes approaches for local prevention of bacterial infections based on antibiotic-eluting medical devices. These devices include bone cements, fillers and coatings for orthopedic applications, wound dressings based on synthetic and natural polymers, intravascular devices, vascular grafts and periodontal devices. Part of the review is dedicated to our novel composite drug-eluting fibers and structured drug-eluting films, which are designed to be used as basic elements of various devices. In this review emphasis is placed on processing techniques, microstructure, drug release profiles, biocompatibility and other relevant aspects necessary for advancing the therapeutic field of antibiotic-eluting devices.


Asunto(s)
Antibacterianos/administración & dosificación , Infecciones Bacterianas/prevención & control , Equipos y Suministros , Antibacterianos/farmacocinética , Antibacterianos/uso terapéutico , Prótesis Vascular , Materiales Biocompatibles Revestidos/química , Preparaciones de Acción Retardada/química , Sistemas de Liberación de Medicamentos/instrumentación , Sistemas de Liberación de Medicamentos/métodos , Humanos , Periodontitis/tratamiento farmacológico , Periodontitis/prevención & control , Prótesis e Implantes
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