RESUMO
This study investigated the hydrophobic-hydrophilic characteristics of zinc oxide (ZnO) nanorod coatings for potential biomedical applications. We examined the effects of different alignments of ZnO nanorods on the wetting and mechanical characteristics of the coatings. ZnO seed layers were prepared on stainless-steel plates using atomic layer deposition (ALD) at five different temperatures ranging from 50 to 250 °C. The ZnO nanorod coatings were then deposited on these seed layers through chemical bath deposition. The polycrystalline structure of the seed layers and the morphology of the nanorods were analyzed using grazing incidence angle x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Mechanical and wetting properties of the nanorod coatings were examined using nanoindentation and water-droplet tests. The seed layers produced at 50 and 250 °C showed stronger (0 0 2) peaks than the other layers. ZnO nanorods on these seed layers exhibited greater vertical orientation and lower water contact angles indicating a more hydrophilic surface. Additionally, vertically oriented nanorod coatings demonstrated greater elastic modulus and hardness than those of oblique nanorods. Our findings indicate that ALD technology can be used to control the spatial arrangement of ZnO nanorods and optimize the hydrophobic-hydrophilic and mechanical properties of coating surfaces.
RESUMO
BACKGROUND: Conventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative MRI sequences. We aimed to examine a threshold-based fat quantification method in the supraspinatus muscle on standard T1-weighted MR images and compare the threshold-based method with Goutallier grades and MR spectroscopy. METHODS: We retrospectively examined 38 symptomatic patients, who underwent T1 and T2-weighted fast spin-echo MR imaging and a single voxel spin-echo MR spectroscopy. The supraspinatus muscle and fossa were manually segmented in T1-weighted sagittal images and clustering-based thresholding was applied to quantify the fat fractions in the segmented areas using custom MATLAB software. Threshold-based fat fractions were compared with the Goutallier grades and MR spectroscopy fat/water ratios. A one-way analysis of variance and Pearson correlation were tested in the MATLAB software. RESULTS: Inter-observer reliability of threshold-based fat fractions for the supraspinatus muscle and fossa were 0.977 and 0.990 respectively, whereas the reliability of the Goutallier grading was 0.798. Threshold-based fat fractions in the supraspinatus fossa were significantly different between various Goutallier grades (one-way ANOVA, p < 0.001). Threshold-based fat fractions in the supraspinatus muscle strongly correlated with the MR spectroscopy fat/water ratio (Pearson correlation R-square = 0.83). CONCLUSIONS: Threshold-based fat quantification on standard T1-weighted MR images was highly reliable and produced comparable results to conventional Goutallier grades and MR spectroscopy fat/water ratios and could serve as an alternative method for accurate fat quantification in rotator cuff muscles.
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Tecido Adiposo/diagnóstico por imagem , Lesões do Manguito Rotador/diagnóstico por imagem , Manguito Rotador/diagnóstico por imagem , Manguito Rotador/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Estudos Retrospectivos , Manguito Rotador/cirurgia , Lesões do Manguito Rotador/patologia , Lesões do Manguito Rotador/cirurgia , Software , Adulto JovemRESUMO
BACKGROUND: The role of altered joint mechanics on cartilage degeneration in in vivo models has not been studied successfully due to a lack of pre-injury information. We aimed 1) to develop an accurate in vivo canine model to measure the changes in joint loading and T2 star (T2*) relaxation time before and after unilateral supraspinatus tendon resections, and 2) to find the relationship between regional variations in articular cartilage loading patterns and T2* relaxation time distributions. METHODS: Rigid markers were implanted in the scapula and humerus of tested dogs. The movement of the shoulder bones were measured by a motion tracking system during normal gaits. In vivo cartilage contact strain was measured by aligning 3D shoulder models with the motion tracking data. Articular cartilage T2* relaxation times were measured by quantitative MRI scans. Articular cartilage contact strain and T2* relaxation time were compared in the shoulders before and 3 months after the supraspinatus tendon resections. RESULTS: Excellent accuracy and reproducibility were found in our in vivo contact strain measurements with less than 1% errors. Changes in articular cartilage contact strain exhibited similar patterns with the changes in the T2* relaxation time after resection surgeries. Regional changes in the articular cartilage T2* relaxation time exhibited positive correlations with regional contact strain variations 3 months after the supraspinatus resection surgeries. CONCLUSION: This is the first study to measure in vivo articular cartilage contact strains with high accuracy and reproducibility. Positive correlations between contact strain and T2* relaxation time suggest that the articular cartilage extracellular matrix may responds to mechanical changes in local areas.
Assuntos
Cartilagem Articular/diagnóstico por imagem , Imageamento por Ressonância Magnética/veterinária , Manguito Rotador/diagnóstico por imagem , Articulação do Ombro/diagnóstico por imagem , Ombro/fisiologia , Animais , Cães , Força Muscular , Reprodutibilidade dos Testes , Manguito Rotador/cirurgia , Ombro/cirurgia , Articulação do Ombro/cirurgiaRESUMO
Postmeniscectomy osteoarthritis (OA) is hypothesized to be the consequence of abnormal mechanical conditions, but the relationship between postsurgical alterations in articular cartilage strain and in vivo biomechanical/biochemical changes in articular cartilage is unclear. We hypothesized that spatial variations in cartilage nominal strain (percentile thickness change) would correlate with previously reported in vivo articular cartilage property changes following meniscectomy. Cadevaric sheep knees were loaded in cyclic compression which was previously developed to mimic normal sheep gait, while a 4.7 T magnetic resonance imaging (MRI) imaged the whole joint. 3D cartilage strain maps were compared with in vivo sheep studies that described postmeniscectomy changes in shear modulus, phase lag, proteoglycan content and collagen organization/content in the articular cartilage. The area of articular cartilage experiencing high (overloaded) and low (underloaded) strain was significantly increased in the meniscectomized tibial compartment by 10% and 25%, respectively, while no significant changes were found in the nonmeniscectomized compartment. The overloaded and underloaded regions of articular cartilage in our in vitro specimens correlated with regions of in vivo shear modulus reduction. Glycosaminoglycans (GAG) content only increased at the underloaded articular cartilage but decreased at the overloaded articular cartilage. No significant correlation was found in phase lag and collagen organization/content changes with the strain variation. Comparisons between postsurgical nominal strain and in vivo cartilage property changes suggest that both overloading and underloading after meniscectomy may directly damage the cartilage matrix stiffness (shear modulus). Disruption of superficial cartilage by overloading might be responsible for the proteoglycan (GAG) loss in the early stage of postmeniscectomy OA.
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Cartilagem Articular , Glicosaminoglicanos/metabolismo , Articulação do Joelho/metabolismo , Teste de Materiais , Meniscos Tibiais/cirurgia , Resistência ao Cisalhamento , Estresse Mecânico , Animais , Fenômenos Biomecânicos , Articulação do Joelho/cirurgia , OvinosRESUMO
Iatrogenic stomach perforation is a detrimental, irreversible, and fatal condition. Traditional surgery and endoscopic suturing clips and devices have been introduced to seal holes and prevent sepsis and disease progression. However, the development of endoscopic devices for perforations remains challenging, with no standard device available. This study investigates the superficial layer approximation strengths of the newly designed ENDOCRAB system for gastric wall defects. Thirty porcine stomachs were prepared ex vivo for the perforation model and distributed equally into three groups: ENDOCRAB system, Through-the-Scope Clip (TTSC), and hand suturing (HS). Both ENDOCRAB and TTSC achieved mucosal-submucosal layer apposition, whereas HS allowed a full-thickness layer. Their air leakage pressure and procedural duration were measured. The analysis of air-leakage pressure demonstrated comparable suture strength between ENDOCRAB (118.5 ± 41.7 mmHg) and HS (127.4 ± 30.2 mmHg, P = 0.812), but inferior strength with TTSC (73.6 ± 21.6 mmHg, P = 0.012). HS achieved the shortest procedural duration, whereas ENDOCRAB and TTSC showed no significant differences. The ENDOCRAB system showed significantly greater strength than the TTSC, was comparable to HS in strength, and required a procedural duration similar to that of the TTSC. Furthermore, long-term in vivo experiments and histological evaluations are essential.
Assuntos
Cirurgia Endoscópica por Orifício Natural , Gastropatias , Suínos , Animais , Estômago/cirurgia , Técnicas de Sutura , Instrumentos CirúrgicosRESUMO
The objective of this study was to examine the effects of muscle strength training on knee kinematics/kinetics and muscle activation patterns during anticipated side-step cutting. Three-dimensional knee kinematics/kinetics data and muscle activation of selected lower extremity muscles were measured while performing cutting before and after completing 10-week circuit strength training mixed typical resistance training and power training (intervention) or no training (control) from 25 female subjects. The muscle strength of quadriceps and hamstrings were measured before and after training using isokinetic dynamometer. No statistically significant differences were observed in quadriceps and hamstrings muscle strength, all kinematic/kinetic variables, and muscle activation for the control group. Both quadriceps (p = 0.005) and hamstrings (p = 0.030) muscle strength were increased after training. An increased biceps femoris (p = 0.003) and H:Q ratio of activation (p = 0.016), as well as decreased gastrocnemius muscle activation (p = 0.012) during pre-activation phase in intervention group were found. No significant differences were found in knee kinematics and kinetics both at the time frame of the initial contact and the peak tibial anterior shear force after training. In conclusion, muscle strength training altered some muscle activations of lower extremity muscles, which might affect the risk of ACL injury, but it did not change the kinematic/kinetic parameters.
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Articulação do Joelho/fisiologia , Extremidade Inferior/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Treinamento Resistido , Adulto , Fenômenos Biomecânicos/fisiologia , Eletromiografia , Feminino , Humanos , Joelho/fisiologia , Adulto JovemRESUMO
BACKGROUND: Although partial meniscectomy is a common treatment for the tears in the avascular region of the meniscus, mechanical alterations following meniscectomy are known to initiate mechanically-induced osteoarthritis. We aimed to measure the articular cartilage contact pressure distributions in the knees with surgically repaired and partially resected menisci in the avascular region. METHODS: A pneumatic loading device was developed to apply a 1000 N compressive load on the cadaveric porcine knee samples at the flexion angles of 20, 35, 50, and 65°. We simulated longitudinal meniscal tears in the avascular inner 1/3 portion and the well-vascularized middle 1/3 portion of the meniscus. Articular cartilage contact pressures for the knees with intact, torn, repaired, and resected menisci were compared. FINDINGS: For the tears in well-vascularized regions, meniscal repairs restored articular cartilage contact pressures to the levels in intact joints. However, partial meniscectomy significantly increases the maximum contact pressures and the average contact pressures in highly compressed areas. However, partial meniscectomy in the avascular region did not alter the maximum articular cartilage contact pressures and the average contact pressures in highly compressed areas. Stabilities in knee samples were not significantly altered following partial meniscectomy in both inner and middle regions. INTERPRETATION: Although repair surgeries are beneficial for the tears in well-vascularized areas because the articular cartilage contact mechanics are reconstructed, partial meniscectomy may be a viable alternative treatment for the tears in avascular regions without introducing significant mechanical alterations.
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Fenômenos Mecânicos , Meniscectomia , Lesões do Menisco Tibial/cirurgia , Animais , Fenômenos Biomecânicos , Cadáver , Modelos Animais de Doenças , Humanos , Meniscos Tibiais/cirurgia , Pessoa de Meia-Idade , Pressão , SuínosRESUMO
Damage to the acetabular labrum has been associated with cartilage degeneration. Because conventional pressure measurement devices were unable to examine the sealing function of the acetabular labrum on cartilage contact mechanics, we used an image-based computational method to examine how labrectomy affects articular cartilage contact area and strain patterns in porcine hips. Cyclically loaded hip samples were continuously imaged in a CT scanner every 3 min to trace the positions of the femur and acetabulum. Image-based displacement-controlled finite element analysis was used to calculate articular cartilage contact area and nominal strain at different time points. No changes in cartilage contact area were found after labrectomy. Compared to the labrum intact condition, average nominal strain in labrectomized hips was elevated at early time points after load application. The areas of 'high' strain in labrectomized hips were found to be increased by approximately 7% after 30 min of cyclic loading, while the changes in the areas of 'low' strain were minimal. Our result showed that changes in articular cartilage strain following labrectomy were concentrated on locally overloaded areas where the degenerative process of articular cartilage may be initiated.
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Acetábulo/anatomia & histologia , Cartilagem Articular/anatomia & histologia , Acetábulo/diagnóstico por imagem , Acetábulo/cirurgia , Animais , Cartilagem Articular/diagnóstico por imagem , Fêmur/anatomia & histologia , Fêmur/diagnóstico por imagem , Análise de Elementos Finitos , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Articulações/anatomia & histologia , Articulações/diagnóstico por imagem , Pelve/anatomia & histologia , Pelve/diagnóstico por imagem , Pressão , Suínos , Fatores de Tempo , Tomografia Computadorizada por Raios XRESUMO
BACKGROUND: During landing, the ankle angle at initial contact (IC) exhibits relatively wide individual variation compared to the knee and hip angles. However, little is known about the effect of different IC ankle angles on energy dissipation. RESEARCH QUESTION: The purpose of this study was to investigate the relationship between individual ankle angles at IC and energy dissipation in the lower extremity joints. METHODS: Twenty-seven adults performed single-leg landings from a 0.3-m height. Kinetics and kinematics of the lower extremity joints were measured. The relationship between ankle angles at IC and negative work, range of motion, the time to peak ground reaction force, and peak loading rate were analyzed. RESULTS: The ankle angle at IC was positively correlated with ankle negative work (râ¯=â¯0.80, R2â¯=â¯0.64, pâ¯<â¯0.001) and the contribution of the ankle to total (ankle, knee and hip joint) negative work (râ¯=â¯0.84, R2â¯=â¯0.70, pâ¯<â¯0.001), but the ankle angle was negatively correlated with hip negative work (râ¯=â¯-0.46, R2â¯=â¯0.21, pâ¯=â¯0.01) and the contribution of the hip to total negative work (râ¯=â¯-0.61, R2â¯=â¯0.37, p <â¯0.001). The knee negative work and the contribution of the knee to total negative work were not correlated with the ankle angle at IC. The ankle angle at IC was positively correlated with total negative work (râ¯=â¯0.50, R2â¯=â¯0.25, pâ¯<â¯0.01) and negatively correlated with the peak loading rate (râ¯=â¯-0.76, R2â¯=â¯0.57, pâ¯<â¯0.001). SIGNIFICANCE: These results indicated that landing mechanics changed as the ankle angle at IC increased, such that the ankle energy dissipation increased and redistributed the energy dissipation in the ankle and hip joints. Further, these results suggest that increased ankle energy dissipation with a higher IC plantar flexion angle may be a potential landing technique for reducing the risk of injury to the anterior cruciate ligament and hip musculature.
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Articulação do Tornozelo/fisiologia , Articulação do Quadril/fisiologia , Articulação do Joelho/fisiologia , Extremidade Inferior/fisiologia , Movimento/fisiologia , Amplitude de Movimento Articular/fisiologia , Ligamento Cruzado Anterior/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Adulto JovemRESUMO
The growth plate (physis) is responsible for long bone growth through endochondral ossification, a process which can be mechanically modulated. However, our understanding of the detailed mechanical behavior of physeal cartilage occurring in vivo is limited. In this study, we aimed to quantify the time-dependent deformational behavior of physeal cartilage in intact knees under physiologically realistic dynamic loading, and compare physeal cartilage deformation with articular cartilage deformation. A 4.7 T MRI scanner continuously scanned a knee joint in the sagittal plane through the central load-bearing region of the medial compartment every 2.5 min while a realistic cyclic loading was applied. A custom auto-segmentation program was developed to delineate complex physeal cartilage boundaries. Physeal volume changes at each time step were calculated. The new auto-segmentation was found to be reproducible with COV of the volume measurements being less than 0.5%. Time-constants of physeal cartilage consolidation (1.31±0.74 min) and recovery (1.63±0.70 min) were significantly smaller than the values (5.53±1.78/17.71±13.88 min for consolidation/recovery) in articular cartilage (P<0.05). The rapid consolidation and recovery of physeal cartilage may due to a relatively free metaphyseal fluid boundary which would allow rapid fluid exchange with the adjacent cancellous bone. This may impair the generation of hydrostatic pressure in the cartilage matrix when the physis is under chronic compressive loading, and may be related to the premature ossification of the growth plate under such conditions. Research on the growth plate fluid exchange may provide a more comprehensive understanding of mechanisms and disorders of long bone growth.
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Lâmina de Crescimento/fisiologia , Articulação do Joelho/fisiologia , Suporte de Carga/fisiologia , Animais , Lâmina de Crescimento/anatomia & histologia , OvinosRESUMO
The acetabular labrum is believed to have a sealing function. However, a torn labrum may not effectively prevent joint fluid from escaping a compressed joint, resulting in impaired lubrication. We aimed to understand the role of the acetabular labrum in maintaining a low friction environment in the hip joint. We did this by measuring the resistance to rotation (RTR) of the hip, which reflects the friction of the articular cartilage surface, following focal and complete labrectomy. Five cadaveric hips without evidence of osteoarthritis and impingement were tested. We measured resistance to rotation of the hip joint during 0.5, 1, 2, and 3 times body weight (BW) cyclic loading in the intact hip, and after focal and complete labrectomy. Resistance to rotation, which reflects articular cartilage friction in an intact hip was significantly increased following focal labrectomy at 1-3 BW loading, and following complete labrectomy at all load levels. The acetabular labrum appears to maintain a low friction environment, possibly by sealing the joint from fluid exudation. Even focal labrectomy may result in increased joint friction, a condition that may be detrimental to articular cartilage and lead to osteoarthritis.
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Cartilagem Articular/fisiopatologia , Articulação do Quadril/patologia , Acetábulo/fisiopatologia , Acetábulo/cirurgia , Idoso , Idoso de 80 Anos ou mais , Cadáver , Feminino , Fricção , Articulação do Quadril/fisiopatologia , Humanos , Masculino , Estresse Mecânico , Suporte de CargaRESUMO
Meniscectomy is a significant risk factor for osteoarthritis, involving altered cell synthesis, central fibrillation, and peripheral osteophyte formation. Though changes in articular cartilage contact pressure are known, changes in tissue-level mechanical parameters within articular cartilage are not well understood. Recent imaging research has revealed the effects of meniscectomy on the time-dependent deformation of physiologically loaded articular cartilage. To determine tissue-level cartilage mechanics that underlie observed deformation, a novel finite element modeling approach using imaging data and a contacting indenter boundary condition was developed. The indenter method reproduces observed articular surface deformation and avoids assumptions about tangential stretching. Comparison of results from an indenter model with a traditional femur-tibia model verified the method, giving errors in displacement, solid and fluid stress, and strain below 1% (RMS) and 7% (max.) of the absolute maximum of the parameters of interest. Indenter finite element models using real joint image data showed increased fluid pressure, fluid exudation, loss of fluid load support, and increased tensile strains centrally on the tibial condyle after meniscectomy-patterns corresponding to clinical observations of cartilage matrix damage and fibrillation. Peripherally there was decreased consolidation, which corresponds to reduced contact and fluid pressure in this analysis. Clinically, these areas have exhibited advance of the subchondral growth front, biological destruction of the cartilage matrix, cartilage thinning, and eventual replacement of the cartilage via endochondral ossification. Characterizing the changes in cartilage mechanics with meniscectomy and correspondence with observed tissue-level effects may help elucidate the etiology of joint-level degradation seen in osteoarthritis.
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Cartilagem Articular/fisiologia , Meniscos Tibiais/cirurgia , Osteoartrite/fisiopatologia , Algoritmos , Fenômenos Biomecânicos , Análise de Elementos Finitos , Humanos , Processamento de Imagem Assistida por Computador , Cinética , Imageamento por Ressonância Magnética/métodos , Modelos Teóricos , Pressão , Reprodutibilidade dos Testes , Fatores de Risco , Estresse MecânicoRESUMO
The structure and function of the proximal hip joint capsule and the zona orbicularis are poorly understood. We hypothesized that the zona orbicularis is an important contributor to hip stability in distraction. In seven cadaveric hip specimens from seven male donors we distracted the femur from the acetabulum in a direction parallel to the femoral shaft with the hip in the neutral position. Eight sequential conditions were assessed: (1) intact specimen (muscle and skin removed), (2) capsule vented, (3) incised iliofemoral ligament, (4) circumferentially incised capsule, (5) partially resected capsule (distal to the zona orbicularis), (6) completely resected capsule, (7) radially incised labrum, and (8) completely resected labrum. The reduction of the distraction load was greatest between the partially resected capsule phase and completely resected capsule phase at 1, 3, and 5 mm joint distraction (p = 0.018). The proximal to middle part of the capsule, which includes the zona orbicularis, appears grossly and biomechanically to act as a locking ring wrapping around the neck of the femur and is a key structure for hip stability in distraction.