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1.
IEEE Trans Biomed Eng ; 70(2): 735-746, 2023 02.
Artículo en Inglés | MEDLINE | ID: mdl-36006884

RESUMEN

Surgical simulators are safe and evolving educational tools for developing surgical skills. In particular, virtual and hybrid simulators are preferred due to their detailedness, customization and evaluation capabilities. To accelerate the revolution of a novel class of hybrid simulators, a Smart Artificial Soft Tissue is presented here, that determines the relative position of conductive surgical instruments in artificial soft tissue by inverse resistance mappings without the need for a fixed reference point. This is particularly beneficial for highly deformable structures when specific target regions need to be reached or avoided. The carbon-black-silicone composite used can be shaped almost arbitrarily and its elasticity can be tuned by modifying the silicone base material. Thus, objective positional feedback for haptically correct artificial soft tissue can be ensured. This is demonstrated by the development of a laryngeal phantom to simulate the implantation of laryngeal pacemaker electrodes. Apart from the position-detecting larynx phantom, the simulator uses a tablet computer for the virtual representation of the vocal folds' movements, in accordance with the electrical stimulation by the inserted electrodes. The possibility of displaying additional information about target regions and anatomy is intended to optimize the learning progress and illustrates the extensibility of hybrid surgical simulators.


Asunto(s)
Laringe , Marcapaso Artificial , Pliegues Vocales , Aprendizaje , Retroalimentación , Simulación por Computador
2.
J Mech Behav Biomed Mater ; 110: 103946, 2020 10.
Artículo en Inglés | MEDLINE | ID: mdl-32957238

RESUMEN

The force experienced while inserting an 18-gauge Tuohy needle into the epidural space or dura is one of only two feedback components perceived by an anaesthesiologist to deduce the needle tip position in a patient's spine. To the best of the authors knowledge, no x-ray validated measurements of these forces are currently available to the public. A needle insertion force recording during an automated insertion of an 18-gauge Tuohy needle into human vertebral segments of four female donors was conducted. During the measurements, x-ray images were recorded simultaneously. The force peaks due to the penetration of the ligamentum supraspinale and ligamentum flavum were measured and compared to the measurements of an artificial patient phantom for a hybrid patient simulator. Based on these force peaks and the slope of the ligamentum interspinale, a mathematical model was developed. The model parameters were used to compare human specimens and artificial patient phantom haptics. The force peaks for the ligamenta supraspinale and flavum were 7.55 ± 3.63 N and 15.18 ± 5.71 N, respectively. No significant differences were found between the patient phantom and the human specimens for the force peaks and four of six physical model parameters. The patient phantom mimics the same resistive force against the insertion of an 18-gauge Tuohy needle. However, there was a highly significant (p < 0.001, effsize = 0.949 and p < 0.001, effsize = 0.896) statistical difference observed in the insertion depth where the force peaks of the ligamenta supraspinale and flavum were detected between the measurements on the human specimens and the patient phantom. Within this work, biomechanical evidence was identified for the needle insertion force into human specimens. The comparison of the measured values of the human vertebral segments and the artificial patient phantom showed promising results.


Asunto(s)
Anestesia Epidural , Ligamento Amarillo , Duramadre , Espacio Epidural , Femenino , Humanos , Agujas
3.
MAGMA ; 33(6): 819-828, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32458188

RESUMEN

OBJECTIVE: To develop and validate a 3D registration approach by which double echo steady state (DESS) MR images with cartilage thickness segmentations are used to extract the cartilage transverse relaxation time (T2) from multi-echo-spin-echo (MESE) MR images, without direct segmentations for MESE. MATERIALS AND METHODS: Manual DESS segmentations of 89 healthy reference knees (healthy) and 60 knees with early radiographic osteoarthritis (early ROA) from the Osteoarthritis Initiative were registered to corresponding MESE images that had independent direct T2 segmentations. For validation purposes, (a) regression analysis of deep and superficial cartilage T2 was performed and (b) between-group differences between healthy vs. early ROA knees were compared for registered vs. direct MESE analysis. RESULTS: Moderate to high correlations were observed for the deep (r = 0.80) and the superficial T2 (r = 0.81), with statistically significant between-group differences (ROA vs. healthy) of + 1.4 ms (p = 0.002) vs. + 1.3 ms (p < 0.001) for registered vs. direct T2 segmentation in the deep, and + 1.3 ms (p = 0.002) vs. + 2.3 ms (p < 0.001) in the superficial layer. DISCUSSION: This registration approach enables extracting cartilage T2 from MESE scans using DESS (cartilage thickness) segmentations, avoiding the need for direct MESE T2 segmentations.


Asunto(s)
Cartílago Articular , Osteoartritis de la Rodilla , Cartílago Articular/diagnóstico por imagen , Humanos , Rodilla/diagnóstico por imagen , Articulación de la Rodilla/diagnóstico por imagen , Imagen por Resonancia Magnética , Osteoartritis de la Rodilla/diagnóstico por imagen
4.
J Mech Behav Biomed Mater ; 97: 247-253, 2019 09.
Artículo en Inglés | MEDLINE | ID: mdl-31132661

RESUMEN

Artificial bones made of polyurethane are frequently used as an alternative to human bone for biomechanical testing. However, the biomechanical characteristics of these materials are often not validated against those of human bones. Thus, synthetic bone surrogates reflecting procedure-specific biomechanical properties of human bones are necessary for reliable implant design and testing. The aim of this study was to evaluate novel custom made open- and close-cell bone surrogates through morphometry assessment and pedicle screw pullout tests as an alternative to human bone for biomechanical testing. Bone surrogates created from polyurethane resin, mineral fillers and varying amounts of blowing agent were customized to various densities. Pedicle screws were manually inserted and pullout tests with a feed rate of 1 mm/min were conducted until failure. Load and displacement curves were recorded and analyzed in terms of maximum pullout forces. The resulting pullout forces of open- (1437 ±â€¯665 N) and close-cell surrogates (951 ±â€¯578 N) showed comparable results to human bone (1417 ±â€¯812N) used as a reference. Furthermore, structural morphometric parameters were in accordance with human vertebral cancellous bone. In conclusion, the customized bone surrogates provide a new opportunity to design and test pedicle screws and further study the relationship between biomechanical properties and apparent density of artificial spongy bone.


Asunto(s)
Sustitutos de Huesos/química , Tornillos Pediculares , Poliuretanos/química , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Femenino , Humanos , Masculino , Ensayo de Materiales , Persona de Mediana Edad , Presión , Columna Vertebral/patología , Tomografía Computarizada por Rayos X
5.
J Hazard Mater ; 370: 70-79, 2019 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-29153855

RESUMEN

Microbiome analyses of soils and microcosm experiments depend on conditions that include sterilization in order to perform experimental manipulation of microbial communities. Still, they should represent conditions close to nature. When using metal contaminated soils, sterilization methods might alter metal availability. Here, four typical metal contaminated substrates were analyzed, representing different contamination histories and soil types. They included two very poor substrates, as they are often found at metal contaminated sites. The low contents in organic carbon and nitrogen as well as two substrates with slightly higher nutrient availability were used to perform a comprehesive study for element availability changes induced by sterilization. Autoclaving, dry heat or gamma raγ sterilization were applied and compared to a non-treated control. The sterile substrates were analyzed using sequential extraction to account for different associations of the elements. Metals forming specific (hydro)oxide layers were specifically analyzed since they in turn may also impact other metals or ions. In addition, (heavy) metals and (micro)nutrients were analyzed for changes in speciation. The effects of autoclaving (wet heat) was found acceptable, while γ-ray irradiation did show unexpected changes in metal associations, especially for one substrate. Dry heat changed metal availability to the highest degree.

6.
J Endocrinol ; 240(1): 15-26, 2019 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-30400069

RESUMEN

Aldosterone is a key factor in adverse cardiovascular remodeling by acting on the mineralocorticoid receptor (MR) in different cell types. Endothelial MR activation mediates hypertrophy, inflammation and fibrosis. Cardiovascular remodeling is often accompanied by impaired angiogenesis, which is a risk factor for the development of heart failure. In this study, we evaluated the impact of MR in endothelial cells on angiogenesis. Deoxycorticosterone acetate (DOCA)-induced hypertension was associated with capillary rarefaction in the heart of WT mice but not of mice with cell type-specific MR deletion in endothelial cells. Consistently, endothelial MR deletion prevented the inhibitory effect of aldosterone on the capillarization of subcutaneously implanted silicon tubes and on capillary sprouting from aortic ring segments. We examined MR-dependent gene expression in cultured endothelial cells by RNA-seq and identified a cluster of differentially regulated genes related to angiogenesis. We found opposing effects on gene expression when comparing activation of the mineralocorticoid receptor in ECs to treatment with vascular endothelial growth factor (VEGF), a potent activator of angiogenesis. In conclusion, we demonstrate here that activation of endothelial cell MR impaired angiogenic capacity and lead to capillary rarefaction in a mouse model of MR-driven hypertension. MR activation opposed VEGF-induced gene expression leading to the dysregulation of angiogenesis-related gene networks in endothelial cells. Our findings underscore the pivotal role of endothelial cell MR in the pathophysiology of hypertension and related heart disease.


Asunto(s)
Aldosterona/farmacología , Células Endoteliales/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Neovascularización Fisiológica/efectos de los fármacos , Receptores de Mineralocorticoides/metabolismo , Factor A de Crecimiento Endotelial Vascular/farmacología , Animales , Aorta/metabolismo , Aorta/fisiopatología , Células Cultivadas , Acetato de Desoxicorticosterona , Modelos Animales de Enfermedad , Células Endoteliales/fisiología , Perfilación de la Expresión Génica , Redes Reguladoras de Genes , Humanos , Hipertensión/inducido químicamente , Hipertensión/metabolismo , Hipertensión/fisiopatología , Masculino , Ratones Noqueados , Ratones Transgénicos , Neovascularización Fisiológica/genética , Receptores de Mineralocorticoides/genética , Factor A de Crecimiento Endotelial Vascular/genética , Remodelación Ventricular/efectos de los fármacos , Remodelación Ventricular/genética
7.
J Mech Behav Biomed Mater ; 91: 159-163, 2019 03.
Artículo en Inglés | MEDLINE | ID: mdl-30580158

RESUMEN

Onlay graft bone augmentation is a standard practice to restore the loss of height of the alveolar ridge following loss of a tooth. Cranial grafts, lifted from the parietal bone, are sandwiched and used to bridge the bony defect in the jaw by means of small screws. During the elevation of the covering gum and subsequent screw placement, care has to be taken in order to preserve underlying nerves. Therefore, to avoid harm to the patient, a solid education of surgeons is essential, which requires training and experience. A simulator for cranial graft-lift training was already developed and shall be expanded to train the augmentation of the lifted implants. Therefore, in this study, synthetic bones for onlay block graft screw placement with realistic haptics for the screw application training were evaluated and compared with human specimens. Six different polyurethane based bone surrogate composites, enriched with varying amounts of calcium-based mineral fillers and blowing agents, were developed. The haptical properties of these synthetic bones were validated for screw placement and compared with human parietal bone specimens. For that, bones were pre-drilled, screws were automatically inserted using a customized testbench and the slope of the screw-insertion torques were analyzed. The slope of the screw insertion torques of the human reference bones was 56.5 ±â€¯14.0 * 10-3 Nm/deg, Surrogates with lower amounts of mineral fillers and blowing agents showed lower torques than the human bone. Synthetic bones, validated for drilling, milling and sawing in an earlier study, also achieved significantly lower torques, which were only the half of the human parietal bones. Two intermediate stages of the aforementioned material compositions, consisting of 75% mineral filler with 0.75% blowing agent and 100% mineral filler with 1.00% blowing agent revealed results comparable with human bone (57.4 ±â€¯10.2 *10-3 Nm/deg, p = 0.893 and 54.9 ±â€¯11.1 *10-3 Nm/deg, p = 0.795, respectively). In conclusion, our findings suggest that, two newly developed polyurethane-based materials mimicking the haptical properties of an onlay bone graft screw fixation, have been identified. Thus, these surrogates are capable of mimicking real bone tissue in our simulator for the education of novice surgeons.


Asunto(s)
Biomimética/instrumentación , Trasplante Óseo/instrumentación , Torque , Anciano , Tornillos Óseos , Trasplante Óseo/educación , Retroalimentación , Femenino , Humanos , Percepción del Tacto
8.
J Mater Sci Mater Med ; 29(10): 153, 2018 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-30269238

RESUMEN

Vertebral augmentation techniques are used to stabilize impacted vertebrae. To minimize intraoperative risks, a solid education of surgeons is desirable. Thus, to improve education of surgeons as well as patient safety, the development of a high-fidelity simulator for the surgical training of cement augmentation techniques was initiated. The integrated synthetic vertebrae should be able to provide realistic haptics during all procedural steps. Synthetic vertebrae were developed, tested and validated with reference to human vertebrae. As a further reference, commercially available vertebrae surrogates for orthopedic testing were investigated. To validate the new synthetic vertebrae, characteristic mechanical parameters for tool insertion, balloon dilation pressure and volume were analyzed. Fluoroscopy images were taken to evaluate the bone cement distribution. Based on the measurement results, one type of synthetic vertebrae was able to reflect the characteristic parameters in comparison to human vertebrae. The different tool insertion forces (19.7 ± 4.1, 13.1 ± 0.9 N, 1.5 ± 0.2 N) of the human reference were reflected by one bone surrogate (11.9 ± 9.8, 24.3 ± 3.9 N, 2.4 ± 1.0 N, respectively). The balloon dilation pressure (13.0 ± 2.4 bar), volume (2.3 ± 1.5 ml) of the synthetic vertebrae were in good accordance with the human reference (10.7 ± 3.4 bar, 3.1 ± 1.1 ml). Cement application forces were also in good accordance whereas the cement distribution couldn't be reproduced accurately. Synthetic vertebrae were developed that delivered authentic haptics during transpedicular instrument insertion, balloon tamp dilation and bone cement application. The validated vertebra model will be used within a hybrid simulator for minimally invasive spine surgery to educate and train surgeons.


Asunto(s)
Cementos para Huesos/química , Vértebras Lumbares/química , Poliuretanos/química , Fracturas de la Columna Vertebral/cirugía , Fenómenos Biomecánicos , Sustitutos de Huesos/química , Femenino , Humanos , Inyecciones , Cifoplastia , Vértebras Lumbares/cirugía , Procedimientos Quirúrgicos Mínimamente Invasivos , Agujas
9.
J Mater Sci Mater Med ; 29(9): 135, 2018 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-30120585

RESUMEN

Cranial grafts are favored to reconstruct skeletal defects because of their reduced resorption and their histocompatibility. Training possibilities for novice surgeons include the "learning by doing" on the patient, specimens or simulators. Although the acceptance of simulators is growing, the major drawback is the lack of validated bone models. The aim of this study was to create and validate a realistic skull cap model and to show superiority compared to a commercially available skull model. Characteristic forces during machinery procedures were recorded and thickness parameters from the bony layers were obtained. The thickness values of the bone layers of the developed parietal bone were comparable to the human ones. Differences between drilling and sawing forces of human and artificial bones were not detected using statistical analysis. In contrast the parameters of the commercially available skull model were significantly different. However, as a result, a model-based simulator for tabula externa graft lift training, consisting of a brain, skull bone cap and covering soft tissues was created. This simulator enables the training of all procedural steps of a "split thickness graft lift". In conclusion, an artificial skull cap suitable for parietal graft lift training was manufactured and validated against human parietal bones.


Asunto(s)
Cráneo/cirugía , Cirugía Bucal/educación , Cirugía Bucal/instrumentación , Trasplante Óseo , Simulación por Computador , Diseño de Equipo , Retroalimentación , Humanos , Modelos Anatómicos , Enseñanza , Tacto , Microtomografía por Rayos X
10.
IEEE Trans Biomed Eng ; 65(8): 1852-1858, 2018 08.
Artículo en Inglés | MEDLINE | ID: mdl-29989924

RESUMEN

OBJECTIVE: The development of a novel hybrid patient simulator was initiated to provide a safe training possibility for novice surgeons. Integrated artificial vertebrae should be able to realistically mimic the haptics of transpedicular vertebroplasty instrument insertion and pedicle screw placement. Therefore, new open-celled material compositions were developed, tested, and validated with reference to elderly human vertebrae. METHODS: Vertebroplasty tool insertion force and pedicle screw torque measurements were performed. To validate the new bone surrogates for transpedicular tool insertion, a novel parametric model of the procedure was developed identifying three characteristic insertion parameters (weighting factors, cutting, and clamping forces). Furthermore, the slope of the insertion torque was used to validate the new materials against the human vertebrae for pedicle screw placement. RESULTS: A relative error less than 6% confirmed the suitability of the parametric model for validation. The weighting factors () and the clamping forces ( ) of the human reference were met by the bone surrogate with 1.25% of blowing agent ( and , respectively). However, no material was able to reflect the instrument cutting forces. The slope obtained during pedicle screw placement in human vertebrae was  Nm/m. The material composition with 1% blowing agent achieved similar results ( N m/m). CONCLUSION: Two suitable materials that deliver realistic haptics during both instrument insertions were validated. The parametric model suitably modeled the transpedicular instrument insertion. SIGNIFICANCE: These newly developed models provide a realistic haptic feedback during transpe-dicular instrument insertions with the potential of cement application during surgical skill training.


Asunto(s)
Procedimientos Ortopédicos/educación , Cirujanos Ortopédicos/educación , Columna Vertebral , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos/fisiología , Tornillos Óseos , Femenino , Humanos , Masculino , Modelos Anatómicos , Columna Vertebral/anatomía & histología , Columna Vertebral/fisiología , Columna Vertebral/cirugía , Torque
11.
J Craniomaxillofac Surg ; 46(8): 1390-1394, 2018 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-29884316

RESUMEN

PURPOSE: Surgical skills can be improved through practical exercise. The use of specimens, human as well as animal, or live animals for surgical training is limited due to ethical concerns. Drawbacks of simulators are costs, fidelity and creditibility. Thus, simulators must be evaluated objectively to determine their validity before they can be used as teaching modalities. The aim of this study was to verify the face content and construct validity of a novel model-based simulator for lifting tabula externa transplants from the parietal skull. MATERIALS AND METHODS: Participants were invited to perform a tabula externa graft lift during a training session on the simulator. Task performance was analyzed with a standardized assessment tool evaluating realism and appropriateness. Specialist ratings were used to evaluate the performance of the participants. This was an exploratory study using a questionnaire, at Kepler University Hospital, Linz, Austria, a university hospital. According to their expertise in craniomaxillofacial surgery, 17 participants were subdivided into 3 groups: 8 novices, 7 experts and 2 raters. RESULTS: The face validity (realism) obtained an average score of 4.2 of a maximum of 5 points. Likewise, the content validity (appropriateness as a teaching modality) obtained an average score of 4.8 of maximum 5 points. No differences were found between experts and novices concerning the recorded surgery completion times (p = 0.418) or the sizes of the lifted grafts (p = 0.110). During the evaluation of task performance, the expert surgeons (46.9 ± 3.7) were graded significantly better than the novices (36.4 ± 8.5), which proved the construct validity of the simulator (p = 0.001). CONCLUSION: All investigated validities were confirmed and approved the simulator as a valid training tool for parietal graft lift.


Asunto(s)
Simulación por Computador , Cráneo/cirugía , Adulto , Trasplante Óseo/educación , Trasplante Óseo/métodos , Competencia Clínica , Huesos Faciales/cirugía , Huesos Faciales/trasplante , Femenino , Humanos , Masculino , Hueso Parietal/cirugía , Hueso Parietal/trasplante , Reproducibilidad de los Resultados , Cráneo/trasplante
12.
J Surg Educ ; 75(4): 1127-1134, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29396275

RESUMEN

OBJECTIVE: The popularity of simulation in the medical field has increased dramatically over the last decades. However, the majority of studies focused on laparoscopic or other endoscopic procedures. In this study, participants performed an image-guided surgery task on a novel spine simulator. Face, content, construct, and concurrent validity were examined. DESIGN: A surgical access through both pedicles (transpedicular) into the vertebral body of artificial L3 vertebrae was performed. Questionnaires, a simulation-based performance score, and a specialist rating were used to evaluate the various forms of validity. SETTING: Klinikum Wels-Grieskirchen, Wels, Austria; tertiary hospital PARTICIPANTS: According to their expertise in image-guided surgery and pedicle tool insertions, 43 participants were subdivided into 3 groups: 22 novices, 12 intermediates, and 9 experts. RESULTS: Of the novice group, the vast majorities were impressed with the attractiveness and the general appearance of the simulator. The majority of intermediates (92%) and experts (89%) would recommend the simulator to others. According to a simulation-based performance score, experts performed significantly better than novices (p = 0.001, d = 1.52) and intermediates (p = 0.01, d = 1.26). The association between the simulation-based performance score and the specialist rating was strong (R = 0.86, p < 0.01). CONCLUSIONS: The novel spine simulator provides an applicable tool for the training of image-guided surgery skills in a realistic design. Its simulation-based assessment score classifies different levels of expertise accurately.


Asunto(s)
Vértebras Lumbares/cirugía , Entrenamiento Simulado/métodos , Cirugía Asistida por Computador/métodos , Austria , Educación Médica Continua , Educación de Postgrado en Medicina , Diseño de Equipo , Humanos , Cirugía Asistida por Computador/instrumentación , Instrumentos Quirúrgicos , Encuestas y Cuestionarios
13.
Curr Stem Cell Res Ther ; 13(3): 174-184, 2018 Feb 23.
Artículo en Inglés | MEDLINE | ID: mdl-28969580

RESUMEN

BACKGROUND: Articular cartilage defects often result in pain, loss of function and finally osteoarthritis. Developing cell-based therapies for cartilage repair is a major goal of orthopaedic research. Autologous chondrocyte implantation is currently the gold standard cell-based surgical procedure for the treatment of large, isolated, full thickness cartilage defects. Several disadvantages such as the need for two surgical procedures or hypertrophic regenerative cartilage, underline the need for alternative cell sources. OBJECTIVE: Mesenchymal stem cells, particularly synovium-derived mesenchymal stem cells, represent a promising cell source. Synovium-derived mesenchymal stem cells have attracted considerable attention since they display great chondrogenic potential and less hypertrophic differentiation than mesenchymal stem cells derived from bone marrow. The aim of this review was to summarize the current knowledge on the chondrogenic potential for synovial stem cells in regard to cartilage repair purposes. RESULTS: A literature search was carried out identifying 260 articles in the databases up to January 2017. Several in vitro and initial animal in vivo studies of cartilage repair using synovia stem cell application showed encouraging results. Since synvoium-derived stem cells are located in the direct vicinity of cartilage and cartilage lesions these cells might even contribute to natural cartilage regeneration. The only one published human in vivo study with 10 patients revealed good results concerning postoperative outcome, MRI, and histologic features after a two-stage implantation of synovial stem cells into an isolated cartilage defect of the femoral condyle. CONCLUSION: Synovium-derived stem cells possess great chondrogenic potential and showed encouraging results for cartilage repair purposes. Furthermore, synovial stem cells play an important role in joint homeostasis and possibly in natural cartilage repair. Further studies are needed to elucidate the interplay of synovial stem cells and chondrocytes, and the promising role of synovium-derived stem cells in cartilage tissue engineering.


Asunto(s)
Enfermedades de los Cartílagos/terapia , Trasplante de Células Madre/métodos , Cartílago Articular , Condrogénesis , Femenino , Humanos , Masculino , Medicina Regenerativa , Células Madre/fisiología , Membrana Sinovial , Trasplante Autólogo/métodos
14.
Annu Int Conf IEEE Eng Med Biol Soc ; 2017: 46-49, 2017 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-29059807

RESUMEN

During vertebral surgery, misplaced pedicle screws can harm vital neural and vascular structures. Haptic distinction between cortical and cancellous bone structures is therefore essential for correct screw placement. This tactile experience during pedicle screw placement can be obtained by training on human or animal specimens even if expensive or ethically questionable. In this study, novel synthetic vertebrae were evaluated within a hybrid simulator to provide realistic haptics for the training of spine surgeries. Synthetic vertebrae were custommade of calcium powder-based composites imitating both, cancellous and cortical bone. The mechanical properties of synthetic surrogates were validated for pedicle screw placement and cement augmentation and were compared with those obtained from human vertebrae and insertion torques were analyzed. In human vertebrae pedicle screw torque measurements resulted in mean torque slopes of 82±33Nm/m. Calcium carbonate-based materials achieved lower torques than the human bone whereas calcium phosphate-based bone surrogates showed comparable results. A further differentiation of the calcium phosphate-based vertebrae revealed, that synthetic vertebrae with lower amounts of blowing agent, achieved suitable torques (83 ± 28Nm/m) in comparison to the human reference (p = 0.39). Cement application and subsequent fluoroscopy images confirmed, that the cancellous core of the synthetic vertebrae enabled cement augmentation. In conclusion, our findings suggest, that the artificial bone samples mimic the properties of human bone during pedicle screw placement and cement augmentation and are therefore suitable as synthetic vertebrae in a hybrid surgical simulator.


Asunto(s)
Tornillos Pediculares , Fenómenos Biomecánicos , Cementos para Huesos , Fluoroscopía , Humanos , Vértebras Lumbares , Columna Vertebral , Torque
15.
Mater Sci Eng C Mater Biol Appl ; 76: 1103-1111, 2017 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-28482474

RESUMEN

Artificial materials reflecting the mechanical properties of human bone are essential for valid and reliable implant testing and design. They also are of great benefit for realistic simulation of surgical procedures. The objective of this study was therefore to characterize two groups of self-developed synthetic foam structures by static compressive testing and by microcomputed tomography. Two mineral fillers and varying amounts of a blowing agent were used to create different expansion behavior of the synthetic open-cell foams. The resulting compressive and morphometric properties thus differed within and also slightly between both groups. Apart from the structural anisotropy, the compressive and morphometric properties of the synthetic foam materials were shown to mirror the respective characteristics of human vertebral trabecular bone in good approximation. In conclusion, the artificial materials created can be used to manufacture valid synthetic bones for surgical training. Further, they provide novel possibilities for studying the relationship between trabecular bone microstructure and biomechanical properties.


Asunto(s)
Hueso Esponjoso , Fenómenos Biomecánicos , Humanos , Estrés Mecánico , Microtomografía por Rayos X
16.
J Mech Behav Biomed Mater ; 72: 49-51, 2017 08.
Artículo en Inglés | MEDLINE | ID: mdl-28448921

RESUMEN

Parietal graft lifts are trained on human or animal specimens or are directly performed on patients without extensive training. In order to prevent harm to the patient resulting from fast rotating machinery tools, the surgeon needs to apply appropriate forces. Realistic haptics are essential to identify the varying parietal bone layers and to avoid a penetration of the brain. This however, requires experience and training. Therefore, in this study, bone surrogate materials were evaluated with the aim to provide an anatomically correct artificial skull cap with realistic haptic feedback for graft lift training procedures. Polyurethane composites made of calcium carbonate and calcium phosphate were developed and were used to create customized bone surrogates, imitating both cancellous and cortical bone. Mechanical properties of these surrogates were validated for drilling, milling and sawing by comparison with human parietal bones. For that, surgical tool tips were automatically inserted into artificial and human bones in a customized test bench and the maximum axial insertion forces were analyzed. Axial tool insertion measurements in human parietal bones resulted in mean maximum forces of 1.8±0.5N for drilling, 1.7±0.3N for milling and 0.9±0.1N for sawing. Calcium carbonate-based materials achieved higher forces than the human bone for drilling and milling, and lower forces for sawing. The calcium phosphate-based bone surrogates showed comparable axial insertions forces for all investigated tools and were identified as a suitable surrogate for drilling (p=0.87 and 0.41), milling (p=0.92 and 0.63) and sawing (p=0.11 and 0.76) of the cortical layer and the cancellous bone, respectively. In conclusion, our findings suggest, that a suitable material composition for artificial parietal bones has been identified, mimicking the properties of human bone during surgical machinery procedures. Thus, these materials are suitable for surgical training and education in simulator training.


Asunto(s)
Poliuretanos/química , Cráneo/cirugía , Retroalimentación , Cirugía General/métodos , Humanos , Fenómenos Mecánicos , Ortopedia/métodos , Entrenamiento Simulado
17.
Hypertension ; 67(1): 130-8, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26553231

RESUMEN

Chronic kidney disease has a tremendously increasing prevalence and requires novel therapeutic approaches. Mineralocorticoid receptor (MR) antagonists have proven highly beneficial in the therapy of cardiac disease. The cellular and molecular events leading to cardiac inflammation and remodeling are proposed to be similar to those mediating renal injury. Thus, this study was designed to evaluate and directly compare the effect of MR deletion in endothelial cells on cardiac and renal injury in a model of deoxycorticosterone acetate-induced hypertension. Endothelial MR deletion ameliorated deoxycorticosterone acetate/salt-induced cardiac remodeling. This was associated with a reduced expression of the vascular cell adhesion molecule Vcam1 in MR-deficient cardiac endothelial cells. Ambulatory blood pressure telemetry revealed that the protective effect of MR deletion was independent from blood pressure. Similar to the heart, deoxycorticosterone acetate/salt-induced severe renal injury, including inflammation, fibrosis, glomerular injury, and proteinuria. However, no differences in renal injury were observed between genotypes. In conclusion, MR deletion from endothelial cells ameliorated deoxycorticosterone acetate/salt-induced cardiac inflammation and remodeling independently from alterations in blood pressure but it did not affect renal injury. These findings suggest that the anti-inflammatory mechanism mediating organ protection after endothelial cell MR deletion is specific for the heart versus the kidney.


Asunto(s)
Presión Sanguínea/fisiología , Endotelio Vascular/metabolismo , Hipertensión/metabolismo , Receptores de Mineralocorticoides/metabolismo , Animales , Células Cultivadas , Acetato de Desoxicorticosterona/toxicidad , Modelos Animales de Enfermedad , Endotelio Vascular/fisiopatología , Regulación de la Expresión Génica , Hipertensión/genética , Hipertensión/fisiopatología , Inmunohistoquímica , Riñón/efectos de los fármacos , Riñón/metabolismo , Masculino , Ratones , Ratones Mutantes , Reacción en Cadena de la Polimerasa , ARN/genética , Molécula 1 de Adhesión Celular Vascular/biosíntesis , Molécula 1 de Adhesión Celular Vascular/genética , Remodelación Ventricular
18.
J Athl Train ; 38(3): 252-258, 2003 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-14608436

RESUMEN

OBJECTIVE: To assess adherence in collegiate athletic training rooms to federal drug laws and to describe current practices. DESIGN AND SETTING: We created a survey of drug-law adherence using federal drug laws and administration guidelines and mailed it to randomly selected certified athletic trainers (ATCs) in United States college and university athletic training rooms. Means, standard deviations, and cross-tabulations were calculated to assess demographic information. A nonparametric test (Kruskal-Wallis) was calculated to compare adherence-score means. RESULTS: Adherence scores were collected from 168 college and university ATCs. The data suggest that ATCs in most athletic training rooms are still not complying with federal drug laws. Drug-dispensation and -administration adherence scores ranged from 5 to 20 (20% to 80% adherence) of 25 points. On average, 49.3% of ATCs in athletic training rooms had marginal adherence to federal regulations (12.34 adherence score). The difference between adherence scores and National Collegiate Athletic Association athletic divisions (Division I, II, III, and III/National Association of Intercollegiate Athletics; P <.002) was significant. In most athletic training rooms, ATCs (55.9%) and students (13.3%) dispensed prescription drugs. In addition, ATCs in most athletic training rooms (53.8%) administered any amount of over-the-counter medication as necessary, and many did not record the transaction (46.2%). DISCUSSION: Nine years after the National Collegiate Athletic Association drug-distribution study in university athletic programs, similar problem areas persist, including unqualified personnel dispensing medications, inappropriately packaged and labeled medications, and a lack of record keeping. CONCLUSIONS: Athletic trainers should work in conjunction with members of the sports medicine team to review federal and state laws and revise institutional drug policies and procedures to comply with regulations in order to provide the best health care to student athletes in a legal and safe manner.

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