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1.
Environ Manage ; 60(2): 176-184, 2017 08.
Artículo en Inglés | MEDLINE | ID: mdl-28624912

RESUMEN

A growing population with increasing consumption of milk and dairy require more agricultural output in the coming years, which potentially competes with forests and other natural habitats. This issue is particularly salient in the tropics, where deforestation has traditionally generated cattle pastures and other commodity crops such as corn and soy. The purpose of this article is to review the concepts and discussion associated with reconciling food production and conservation, and in particular with regards to cattle production, including the concepts of land-sparing and land-sharing. We then present these concepts in the specific context of Colombia, where there are efforts to increase both cattle production and protect tropical forests, in order to discuss the potential for landscape planning for sustainable cattle production. We outline a national planning approach, which includes disaggregating the diverse cattle sector and production types, identifying biophysical, and economic opportunities and barriers for sustainable intensification in cattle ranching, and analyzing areas suitable for habitat restoration and conservation, in order to plan for both land-sparing and land-sharing strategies. This approach can be used in other contexts across the world where there is a need to incorporate cattle production into national goals for carbon sequestration and habitat restoration and conservation.


Asunto(s)
Crianza de Animales Domésticos/métodos , Conservación de los Recursos Naturales/métodos , Bosques , Ganado/crecimiento & desarrollo , Crianza de Animales Domésticos/economía , Animales , Secuestro de Carbono , Bovinos , Colombia , Conservación de los Recursos Naturales/economía , Productos Agrícolas/crecimiento & desarrollo , Humanos , Clima Tropical , Zea mays/crecimiento & desarrollo
2.
Asian-Australas J Anim Sci ; 30(7): 1054-1060, 2017 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-28335096

RESUMEN

OBJECTIVE: This study was aimed at evaluating effects of cattle breed resources and alternative mixed-feeding practices on meat productivity and emission intensities from household farming systems (HFS) in Daklak Province, Vietnam. METHODS: Records from Local Yellow×Red Sindhi (Bos indicus; Lai Sind) and 1/2 Limousin, 1/2 Drought Master, and 1/2 Red Angus cattle during the growth (0 to 21 months) and fattening (22 to 25 months) periods were used to better understand variations on meat productivity and enteric methane emissions. Parameters were determined by the ruminant model. Four scenarios were developed: (HFS1) grazing from birth to slaughter on native grasses for approximately 10 h plus 1.5 kg dry matter/d (0.8% live weight [LW]) of a mixture of guinea grass (19%), cassava (43%) powder, cotton (23%) seed, and rice (15%) straw; (HFS2) growth period fed with elephant grass (1% of LW) plus supplementation (1.5% of LW) of rice bran (36%), maize (33%), and cassava (31%) meals; and HFS3 and HFS4 computed elephant grass, but concentrate supplementation reaching 2% and 1% of LW, respectively. RESULTS: Results show that compared to HFS1, emissions (72.3±0.96 kg CH4/animal/life; least squares means± standard error of the mean) were 15%, 6%, and 23% lower (p<0.01) for the HFS2, HFS3, and HFS4, respectively. The predicted methane efficiencies (CO2eq) per kg of LW at slaughter (4.3±0.15), carcass weight (8.8±0.25 kg) and kg of edible protein (44.1±1.29) were also lower (p<0.05) in the HFS4. In particular, irrespective of the HSF, feed supply and ratio changes had a more positive impact on emission intensities when crossbred 1/2 Red Angus cattle were fed than in their crossbred counterparts. CONCLUSION: Modest improvements on feeding practices and integrated modelling frameworks may offer potential trade-offs to respond to climate change in Vietnam.

3.
Arthroscopy ; 32(8): 1671-5, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-27177437

RESUMEN

PURPOSE: To study the degree of surface congruency between the talar dome and humeral head, to determine the size of graft harvestable from the talar dome, and to determine if there are surrogate markers that correspond to a higher degree of surface congruency. METHODS: Computer models of 7 nonmatched humeral heads and 7 talar domes were generated by digital segmentation of magnetic resonance (MR) images. Modeled defect regions of each humeral head were then aligned with medial and lateral surfaces of each talar dome using software to maximally limit surface mismatch. Modeled defect sizes ranging from 24 × 10 mm to 30 × 10 mm were tested. Congruence match of <1 mm separation was then measured. RESULTS: The average surface match between randomly selected talar domes to humeral head surfaces was 87.2% when 1 mm was selected as the maximal acceptable congruence difference. Congruence match was not affected by graft size or laterality of talar dome as source of graft. Matching radius of curvature of talar dome to humeral head and height of donor to recipient correlated with improved congruence match. Under best match conditions, a maximal congruence match of 95.2% was achieved. CONCLUSIONS: The present study indicates that the talar dome can be a potential source of osteochondral allograft for Hill-Sachs lesions with a maximal defect size of 30 × 10 mm for a single graft. Larger graft sizes resulted in decreased success of actual graft harvest as a result of dimensional constraints of the talar dome. Additional studies are required to determine the biomechanical compatibility of this graft. CLINICAL RELEVANCE: The talar dome has a high degree of surface congruency in comparison with the humeral head though the maximal graft size harvestable limits its clinical applicability.


Asunto(s)
Trasplante Óseo/métodos , Cabeza Humeral/cirugía , Modelos Anatómicos , Astrágalo/trasplante , Adolescente , Adulto , Lesiones de Bankart/cirugía , Simulación por Computador , Humanos , Cabeza Humeral/anatomía & histología , Cabeza Humeral/diagnóstico por imagen , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Programas Informáticos , Astrágalo/anatomía & histología , Astrágalo/diagnóstico por imagen , Recolección de Tejidos y Órganos/métodos , Adulto Joven
6.
Urban Transform ; 5(1): 1, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36694624

RESUMEN

City governments and urban universities are well-positioned to play critical roles in advancing urban sustainability transformations. However, in partnering, cities and universities often focus efforts on discrete sustainability-related projects, neglecting the development of long-term relationships and deep, inter-organizational ties that can allow for collaboration on lasting and transformational change. Yet, at both cities and universities there are often individuals who are deeply interested in developing better partnerships that contribute to the sustainability and livability of their communities. This research develops and tests an evidence-based and facilitated process to guide sustainability researchers and municipal practitioners in the development of transformational City-university partnerships for sustainability. The Audacious Partnerships Process was tested by four City-university partnerships including Arizona State University and the City of Tempe, Dublin City University and the City of Dublin, King's College London and the City of Westminster and the National Autonomous University of Mexico and Mexico City. The Audacious Partnerships Process as well as results from post-surveys and interviews following implementation are elaborated. We conclude with key lessons for modifying and implementing the process to contribute to transformative partnership development. Supplementary Information: The online version contains supplementary material available at 10.1186/s42854-022-00045-5.

7.
Child Psychiatry Hum Dev ; 43(4): 544-59, 2012 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-22331442

RESUMEN

The high prevalence and early onset of anxiety disorders have inspired innovative prevention efforts targeting young at-risk children. With parent-child prevention models showing success for older children and adolescents, the goal of this study was to evaluate a parent-child indicated preventive intervention for preschoolers with mild to moderate anxiety symptoms. Sixteen children (ages 3-5) and at least one of their parents participated in Strengthening Early Emotional Development (SEED), a new 10-week intervention with concurrent groups for parents and children. Outcome measures included clinician-rated and parent-rated assessments of anxiety symptoms, as well as measures of emotion knowledge, parent anxiety, and parental attitudes about children's anxiety. Participation in SEED was associated with reduced child anxiety symptoms and improved emotion understanding skills. Parents reported decreases in their own anxiety, along with attitudes reflecting enhanced confidence in their children's ability to cope with anxiety. Reductions in child and parent anxiety were maintained at 3-month follow-up. Findings suggest that a parent-child cognitive-behavioral preventive intervention may hold promise for young children with mild to moderate anxiety. Improvements in parent anxiety and parental attitudes may support the utility of intervening with parents. Fostering increased willingness to encourage their children to engage in new and anxiety-provoking situations may help promote continued mastery of new skills and successful coping with anxiety.


Asunto(s)
Adaptación Psicológica , Trastornos de Ansiedad/prevención & control , Ansiedad/prevención & control , Relaciones Padres-Hijo , Padres/psicología , Preescolar , Emociones , Femenino , Humanos , Masculino , Ajuste Social , Resultado del Tratamiento
8.
J Magn Reson Imaging ; 33(1): 245-51, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-21182147

RESUMEN

PURPOSE: To study the use of an interleaved water-fat (IWF) sequence with a custom-made radiofrequency (RF) coil for high-resolution imaging of arthritic finger joints. MATERIALS AND METHODS: High-resolution finger magnetic resonance imaging (MRI) was performed using a custom-made dedicated RF receiver coil and an IWF sequence. A phantom, a cadaver finger specimen, and the fingers of two normal controls and six arthritic subjects were imaged with a resolution of 156 × 156 × 600 µm. The appearance of anatomic structures on the IWF images were compared with images acquired with a regular sequence. The images were reviewed by two musculoskeletal radiologists for the depiction of anatomical structures and for the presence of abnormalities. RESULTS: The high-resolution images revealed detailed structures of the finger joints not detectable using typical clinical resolution. The IWF sequence gave more realistic depiction of subchondral bone thickness, and avoided false bone erosions displayed in the regular sequence. It also allowed better visualization of ligaments and tendons. CONCLUSION: This pilot study shows the feasibility and the potential usefulness of high-resolution IWF imaging for finger joint evaluation. This technique may be useful for the diagnosis and treatment assessment of arthritis, and for the study of joint disease pathogenesis.


Asunto(s)
Tejido Adiposo/química , Tejido Adiposo/patología , Articulaciones de los Dedos/química , Articulaciones de los Dedos/patología , Aumento de la Imagen/métodos , Imagen por Resonancia Magnética/métodos , Osteoartritis/patología , Algoritmos , Artritis , Estudios de Factibilidad , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Agua
9.
Clin Orthop Relat Res ; 469(1): 95-106, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-20814773

RESUMEN

BACKGROUND: In vivo studies have suggested Caucasians achieve lower average knee flexion than non-Western populations. Some previous studies have also suggested gender may influence condylar AP translation and axial rotation, while others report an absence of such an influence. QUESTIONS/PURPOSES: We determined whether different ethnic and gender groups residing in the United States had different knee translations and rotations. METHODS: Three-dimensional knee rotations and translations were determined for 72 healthy subjects (24 Caucasian men, 24 Caucasian women, 13 Japanese men, 11 Japanese women) from full extension to maximum flexion using a fluoroscopic technique, under in vivo, weightbearing conditions. RESULTS: Although we observed substantial variability in all groups, small differences between groups were found, especially in deep flexion. Japanese women and men and Caucasian women achieved higher maximum flexion (153°, 151°, and 152°, respectively) than Caucasian men (146°). External rotation was higher for these three groups than for Caucasian men. The medial condyle remained more anterior for Caucasian women and all Japanese subjects than for Caucasian men, possibly leading to greater axial rotation and flexion, observed for these three groups. CONCLUSION: We identified small differences in maximum flexion between genders and ethnic groups. While no differences were identified in the lateral condyle translation, the medial condyle remained more stationary and more anterior for the groups that achieved highest (and similar) maximum flexion. Therefore, it may be important for future implant designs to incorporate these characteristics, such that only the lateral condyle experiences greater posterior femoral rollback, while the medial condyle remains more stationary throughout flexion.


Asunto(s)
Pueblo Asiatico , Articulación de la Rodilla/fisiología , Población Blanca , Adulto , Artroplastia de Reemplazo de Rodilla/instrumentación , Fenómenos Biomecánicos , Femenino , Humanos , Imagenología Tridimensional , Japón , Articulación de la Rodilla/diagnóstico por imagen , Prótesis de la Rodilla , Masculino , Diseño de Prótesis , Interpretación de Imagen Radiográfica Asistida por Computador , Rango del Movimiento Articular , Valores de Referencia , Factores Sexuales , Estados Unidos , Soporte de Peso , Adulto Joven
10.
Geogr J ; 177(4): 311-20, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-22180921

RESUMEN

The global food system is coming under increasing strain in the face of urban population growth. The recent spike in global food prices (2007­08) provoked consumer protests, and raised questions about food sovereignty and how and where food will be produced. Concurrently, for the first time in history the majority of the global population is urban, with the bulk of urban growth occurring in smaller-tiered cities and urban peripheries, or 'peri-urban' areas of the developing world. This paper discusses the new emerging spaces that incorporate a mosaic of urban and rural worlds, and reviews the implications of these spaces for livelihoods and food security. We propose a modified livelihoods framework to evaluate the contexts in which food production persists within broader processes of landscape and livelihood transformation in peri-urban locations. Where and how food production persists are central questions for the future of food security in an urbanising world. Our proposed framework provides directions for future research and highlights the role of policy and planning in reconciling food production with urban growth.


Asunto(s)
Agricultura , Países en Desarrollo , Industria de Alimentos , Abastecimiento de Alimentos , Dinámica Poblacional , Factores Socioeconómicos , Agricultura/economía , Agricultura/educación , Agricultura/historia , Características Culturales/historia , Países en Desarrollo/economía , Países en Desarrollo/historia , Industria de Alimentos/economía , Industria de Alimentos/educación , Industria de Alimentos/historia , Abastecimiento de Alimentos/economía , Abastecimiento de Alimentos/historia , Historia del Siglo XXI , Dinámica Poblacional/historia , Política Pública/economía , Política Pública/historia , Población Rural/historia , Factores Socioeconómicos/historia , Población Urbana/historia
11.
Front Public Health ; 9: 690067, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34778164

RESUMEN

Blue Shield of California's Community Health Advocate Program was created to support whole person-health needs by helping individuals of all socio-economic statuses navigate and access community resources, social services, and medical systems. Blue Shield's Health Reimagined team is partnering with medical providers, community resources centers, and community partners to provide intensive person-centered and technology-enabled care to patients, ensuring social needs are met while promoting health equity. A key aspect of the Health Reimagined initiative embeds Community Health Advocates (CHAs) within physician practices serving patients using a payor-agnostic approach, by which Blue Shield aims to increase access to social services and community resources, improve health outcomes, reduce medical costs, and improve overall patient experience. The purpose of this case study is to understand the provider's perspective of embedding a CHA into the care team and the resulting impact on the practice and patients. Blue Shield also sought to identify best practices and barriers of a CHA program within primary and specialty care practices. As part of an ongoing two-year mixed-methods impact evaluation (2019-2021), 10 semi-structured interviews were conducted with a total of 18 providers and office staff at five primary care and specialty practices where CHAs have been embedded. We also conducted two focus groups with the same five CHAs at different points in time. Several themes emerged from the provider, office staff, and CHA interviews. Provider practices found great value in adding a CHA to their care team as the CHA brings flexibility and continuity to patient care. They also found that having access to a CHA with shared life experiences of the communities they served is a key component to the program's success. Providers and staff reported a new understanding of the social determinants of health that impacts a patient's wellbeing with the embedding of a CHA in the care team. Overall, practitioners expressed high satisfaction with the CHA program. During the COVID-19 pandemic, CHAs have been critically important in care, as social needs have increased, and resources have shifted. The CHA program is constantly adapting to address challenges faced by all stakeholders and applying new knowledge to ensure best practices are implemented within the CHA program.


Asunto(s)
COVID-19 , Agentes Comunitarios de Salud , Humanos , Pandemias , Atención Primaria de Salud , SARS-CoV-2
12.
Invest Ophthalmol Vis Sci ; 61(10): 54, 2020 08 03.
Artículo en Inglés | MEDLINE | ID: mdl-32866268

RESUMEN

Purpose: The spatial distribution of collagen fibril dispersion has a significant impact on both corneal biomechanical and optical behaviors. The goal of this study was to demonstrate a novel method to characterize collagen fibril dispersion using intraocular pressure (IOP)-induced changes in corneal optical aberrations for individualized finite-element (FE) modeling. Methods: The method was tested through both numerical simulations and ex vivo experiments. Inflation tests were simulated in FE models with three assumed patterns of collagen fibril dispersion and experimentally on three rhesus monkey corneas. Geometry, matrix stiffness, and the IOP-induced changes in wavefront aberrations were measured, and the collagen fibril dispersion was characterized. An individualized corneal model with customized collagen fibril dispersion was developed, and the estimated optical aberrations were compared with the measured data. Results: For the theoretical investigations, three assumed distributions of fibril dispersion were all successfully characterized. The estimated optical aberrations closely matched the measured data, with average root-mean-square (RMS) differences of 0.29, 0.24, and 0.10 µm for the three patterns, respectively. The overall features of the IOP-induced changes in optical aberrations were estimated for two ex vivo monkey corneas, with average RMS differences of 0.57 and 0.43 µm. Characterization of the fibril dispersion in the third cornea might have been affected by corneal hydration, resulting in an increased RMS difference, 0.8 µm. Conclusions: A more advanced corneal model with individualized distribution of collagen fibril dispersion can be developed and used to improve our ability to understand both biomechanical and optical behaviors of the cornea.


Asunto(s)
Colágeno/fisiología , Córnea/fisiología , Animales , Fenómenos Biomecánicos , Córnea/patología , Análisis de Elementos Finitos , Presión Intraocular , Macaca mulatta , Masculino , Modems , Trastornos de la Visión/etiología , Trastornos de la Visión/patología
13.
Ann Biomed Eng ; 48(3): 905-912, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-32026231

RESUMEN

This paper provides a synopsis of discussions related to biomedical engineering core curricula that occurred at the Fourth BME Education Summit held at Case Western Reserve University in Cleveland, Ohio in May 2019. This summit was organized by the Council of Chairs of Bioengineering and Biomedical Engineering, and participants included over 300 faculty members from 100+ accredited undergraduate programs. This discussion focused on six key questions: QI: Is there a core curriculum, and if so, what are its components? QII: How does our purported core curriculum prepare students for careers, particularly in industry? QIII: How does design distinguish BME/BIOE graduates from other engineers? QIV: What is the state of engineering analysis and systems-level modeling in BME/BIOE curricula? QV: What is the role of data science in BME/BIOE undergraduate education? QVI: What core experimental skills are required for BME/BIOE undergrads? s. Indeed, BME/BIOI core curricula exists and has matured to emphasize interdisciplinary topics such as physiology, instrumentation, mechanics, computer programming, and mathematical modeling. Departments demonstrate their own identities by highlighting discipline-specific sub-specialties. In addition to technical competence, Industry partners most highly value our students' capacity for problem solving and communication. As such, BME/BIOE curricula includes open-ended projects that address unmet patient and clinician needs as primary methods to prepare graduates for careers in industry. Culminating senior design experiences distinguish BME/BIOE graduates through their development of client-centered engineering solutions to healthcare problems. Finally, the overall BME/BIOE curriculum is not stagnant-it is clear that data science will become an ever-important element of our students' training and that new methods to enhance student engagement will be of pedagogical importance as we embark on the next decade.


Asunto(s)
Ingeniería Biomédica/educación , Curriculum , Ciencia de los Datos , Humanos , Estudiantes , Universidades
14.
Ambio ; 48(5): 529-538, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-30448997

RESUMEN

Cities worldwide are rising to the challenge of sustainable development, calling for large-scale and fast-paced transformations towards sustainability. Urban sustainability challenges are now being reframed as a lack of capacity of individuals and organizations to carry out such socio-technical transformations. This article expands on transformative capacity literature by elucidating the concept of actor-centric transformative capacity. It focuses on the unique role city-university partnerships (CUPs) can play in catalyzing and supporting effective urban sustainability transformations. Two case studies on CUPs in Portland, Oregon and Tempe, Arizona are used to identify determinants of actor-centric transformative capacity, their role in the transformative capacity of urban systems, and how they are built through CUPs. The article concludes with strategies for building effective CUPs capable of building actor-centric transformative capacity among university actors and city administrators.


Asunto(s)
Universidades , Arizona , Ciudades , Humanos , Oregon
15.
J Biomech ; 41(2): 390-8, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-17950743

RESUMEN

Use of computational models with kinematic boundary conditions to study the knee joint contact behavior for normal and pathologic knee joints depends on an understanding of the impacts of kinematic uncertainty. We studied the sensitivities of tibio-menisco-femoral joint contact behavior to variations in knee kinematics using a finite element model (FEM) with geometry and kinematic boundary conditions derived from sequences of magnetic resonance (MR) images. The MR images were taken before and after axial compression was applied to the knee joint of a healthy subject. A design of experiments approach was used to study the impact of the variation in knee kinematics on the contact outputs. We also explored the feasibility of using supplementary hip images to improve the accuracy of knee kinematics. Variations in knee kinematics (0.25mm in medial-lateral, 0.1mm in anterior-posterior and superior-inferior translations, and 0.1 degrees in flexion-extension and varus-valgus, 0.25 degrees in external-internal rotations) caused large variations in joint contact behavior. When kinematic boundary conditions resulted in close approximations of the model-predicted joint contact force to the applied force, variations in predictions of contact parameters were also reduced. The combination of inferior-superior and medial-lateral translations accounted for over 70% of variations for all the contact parameters examined. The inclusion of hip images in kinematic calculations improved knee kinematics by matching the femoral head position. Our findings demonstrate the importance of improving the accuracy and precision of knee kinematic measurements, especially when utilized as an input for finite element models.


Asunto(s)
Fuerza Compresiva/fisiología , Fémur/fisiología , Articulación de la Rodilla/fisiología , Meniscos Tibiales/fisiología , Modelos Biológicos , Rango del Movimiento Articular/fisiología , Tibia/fisiología , Fenómenos Biomecánicos/métodos , Simulación por Computador , Fémur/anatomía & histología , Humanos , Articulación de la Rodilla/anatomía & histología , Imagen por Resonancia Magnética/métodos , Masculino , Meniscos Tibiales/anatomía & histología , Persona de Mediana Edad , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Estrés Mecánico , Tibia/anatomía & histología
16.
Comput Methods Biomech Biomed Engin ; 21(3): 287-296, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-29602301

RESUMEN

The optical performance of the human cornea under intraocular pressure (IOP) is the result of complex material properties and their interactions. The measurement of the numerous material parameters that define this material behavior may be key in the refinement of patient-specific models. The goal of this study was to investigate the relative contribution of these parameters to the biomechanical and optical responses of human cornea predicted by a widely accepted anisotropic hyperelastic finite element model, with regional variations in the alignment of fibers. Design of experiments methods were used to quantify the relative importance of material properties including matrix stiffness, fiber stiffness, fiber nonlinearity and fiber dispersion under physiological IOP. Our sensitivity results showed that corneal apical displacement was influenced nearly evenly by matrix stiffness, fiber stiffness and nonlinearity. However, the variations in corneal optical aberrations (refractive power and spherical aberration) were primarily dependent on the value of the matrix stiffness. The optical aberrations predicted by variations in this material parameter were sufficiently large to predict clinically important changes in retinal image quality. Therefore, well-characterized individual variations in matrix stiffness could be critical in cornea modeling in order to reliably predict optical behavior under different IOPs or after corneal surgery.


Asunto(s)
Córnea/fisiología , Fenómenos Ópticos , Anisotropía , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Presión Intraocular , Modelos Biológicos , Reproducibilidad de los Resultados , Estrés Mecánico , Tonometría Ocular
17.
J Biomech ; 40(14): 3178-86, 2007.
Artículo en Inglés | MEDLINE | ID: mdl-17524409

RESUMEN

Correlating massive bone graft strength to parameters derived from non-invasive imaging is important for pre-clinical and clinical evaluation of therapeutic adjuvants designed to improve graft repair. Towards that end, univariate and multivariate regression between measures of graft and callus geometry from micro-CT imaging and torsional strength and rigidity were investigated in a mouse femoral graft model. Four millimeter mid-diaphyseal defects were grafted with live autografts or processed allografts and allowed to heal for 6, 9, 12, or 18 weeks. We observed that allograft remodeling and incorporation into the host remained severely impaired compared to autografts mainly due to the extent of callus formation around the graft, the rate and extent of the graft resorption, and the degree of union between the graft and host bone as judged by post-mechanical testing analysis of the mode of failure. The autografts displayed greater ultimate torque and torsional rigidity compared to the allografts over time. However the biomechanical properties of allografts were equivalent to autografts by 9 weeks but significantly decreased at 12 and 18 weeks. Multivariate regression analysis demonstrated significant statistical correlations between combinations of the micro-CT parameters (graft and callus volume and cross-sectional polar moment of inertia) with the measured ultimate torque and torsional rigidity (adjusted R(2)=44% and 50%, respectively). The statistical correlations approach used in this mouse study could be useful in guiding future development of non-invasive predictors of the biomechanical properties of allografts using clinical CT.


Asunto(s)
Trasplante Óseo/patología , Animales , Densidad Ósea , Curación de Fractura , Ratones , Ratones Endogámicos C57BL , Estrés Mecánico , Tomógrafos Computarizados por Rayos X , Trasplante Homólogo
18.
J Orthop Res ; 35(10): 2233-2242, 2017 10.
Artículo en Inglés | MEDLINE | ID: mdl-28059475

RESUMEN

Little is known about knee-specific factors that influence contact mechanics. Finite Element (FE) models offer a powerful tool to study contact mechanics, but there often exists ambiguity in the exact values of the inputs (e.g., tissue properties), which can result in a range of output values. Our objective was to quantify the reduction in the range of output values (defined herein as "uncertainty") from FE models of the human knee joint when known pre-defined values are used for clinically measurable inputs. To achieve this goal, we applied a statistically augmented FE approach to three human cadaveric knees for which full geometric and kinematic data were available. Two sets of conditions were simulated: All model inputs, clinically measurable or not, were varied to represent a "normal" patient population (Condition 1); subsets of clinically measurable variable inputs were fixed at specific values (called "patient derived inputs," or PDIs) while the other variables were varied over "normal" values (Condition 2). We found that by fixing body mass index and the anterior-posterior position of the meniscal-bony insertion points, model output uncertainty was reduced by one- to three-fifths. The magnitude of uncertainty reduction was strongly influenced by the individual knee. It was observed that knees with great anterior-posterior translation during gait had greater reductions in uncertainty when PDIs were used. This study represents the first step in developing FE models of the human knee joint based on inputs that can be derived from patients in a clinical setting. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2233-2242, 2017.


Asunto(s)
Análisis de Elementos Finitos , Articulación de la Rodilla/fisiología , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Incertidumbre
19.
J Orthop Res ; 23(4): 735-42, 2005 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-16022984

RESUMEN

Although the rabbit hindlimb has been commonly used as an experimental animal model for studies of osteoarthritis, bone growth and fracture healing, the in vivo biomechanics of the rabbit knee joint have not been quantified. The purpose of this study was to investigate the kinematic and kinetic patterns during hopping of the adult rabbit, and to develop a model to estimate the joint contact force distribution between the tibial plateaus. Force platform data and three-dimensional motion analysis using infrared markers mounted on intracortical bone pins were combined to calculate the knee and ankle joint intersegmental forces and moments. A statically determinate model was developed to predict muscle, ligament and tibiofemoral joint contact forces during the stance phase of hopping. Variations in hindlimb kinematics permitted the identification of two landing patterns, that could be distinguished by variations in the magnitude of the external knee abduction moment. During hopping, the prevalence of an external abduction moment led to the prediction of higher joint contact forces passing through the lateral compartment as compared to the medial compartment of the knee joint. These results represent critical data on the in vivo biomechanics of the rabbit knee joint, which allow for comparisons to both other experimental animal models and the human knee, and may provide further insight into the relationships between mechanical loading, osteoarthritis, bone growth, and fracture healing.


Asunto(s)
Fenómenos Biomecánicos/métodos , Marcha/fisiología , Articulación de la Rodilla/fisiología , Modelos Biológicos , Animales , Fenómenos Biomecánicos/instrumentación , Fémur/fisiología , Miembro Posterior/fisiología , Masculino , Músculo Esquelético/fisiología , Conejos , Tibia/fisiología , Soporte de Peso/fisiología
20.
Knee ; 22(5): 405-410, 2015 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-26213361

RESUMEN

BACKGROUND: Several factors are believed to contribute to patellofemoral joint function throughout knee flexion including patellofemoral (PF) kinematics, contact, and bone morphology. However, data evaluating the PF joint in this highly flexed state have been limited. Therefore, the purpose of this study was to evaluate patellofemoral contact and alignment in low (0°), moderate (60°), and deep (140°) knee flexion, and then correlate these parameters to each other, as well as to femoral morphology. METHODS: Sagittal magnetic resonance images were acquired on 14 healthy female adult knees (RSRB approved) using a 1.5 T scanner with the knee in full extension, mid-flexion, and deep flexion. The patellofemoral cartilage contact area, lateral contact displacement (LCD), cartilage thickness, and lateral patellar displacement (LPD) throughout flexion were defined. Intra- and inter-rater repeatability measures were determined. Correlations between patellofemoral contact parameters, alignment, and sulcus morphology were calculated. RESULTS: Measurement repeatability ICCs ranged from 0.94 to 0.99. Patellofemoral cartilage contact area and thickness, LCD, and LPD were statistically different throughout all levels of flexion (p<0.001). The cartilage contact area was correlated to LPD, cartilage thickness, sulcus angle, and epicondylar width (r=0.47-0.72, p<0.05). DISCUSSION: This study provides a comprehensive analysis of the patellofemoral joint throughout its range of motion. CONCLUSIONS: This study agrees with past studies that investigated patellofemoral measures at a single flexion angle, and provides new insights into the relationship between patellofemoral contact and alignment at multiple flexion angles. CLINICAL RELEVANCE: The study provides a detailed analysis of the patellofemoral joint in vivo, and demonstrates the feasibility of using standard clinical magnetic resonance imaging scanners to image the knee joint in deep flexion.


Asunto(s)
Cartílago Articular/anatomía & histología , Imagen por Resonancia Magnética , Movimiento/fisiología , Articulación Patelofemoral/anatomía & histología , Adulto , Cartílago Articular/fisiología , Femenino , Voluntarios Sanos , Humanos , Articulación Patelofemoral/fisiología , Reproducibilidad de los Resultados
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