Mineral heterogeneity has a minor influence on the apparent elastic properties of human cancellous bone: a SRμCT-based finite element study

At the tissue level, the local material properties of human cancellous bone are heterogeneous due to constant remodelling. Since standard high-resolution computed tomography scanning methods are unable to capture this heterogeneity in detail, local differences in mineralisation are normally not incorporated in computational models. To investigate the effects of heterogeneous mineral distribution on the apparent elastic properties, 40 cancellous bone samples from the human femoral neck were scanned by means of synchrotron radiation microcomputed tomography (SRμCT). SRμCT-based micromechanical finite element models that accounted for mineral heterogeneity were compared with homogeneous models. Evaluation of the apparent stiffness tensor of both model types revealed that homogeneous models led to a minor but significant (p < 0.05) overestimation of the elastic properties of heterogeneous models by 2.18 ± 1.89%. Variation of modelling parameters did not affect the overestimation to a great extent. It was concluded that the heterogeneous mineralisation has only a minor influence on the apparent elastic properties of human cancellous bone.     

Stochastic multi-scale prediction on the apparent elastic moduli of trabecular bone considering uncertainties of biological apatite (BAp) crystallite orientation and image-based modelling

An assessment of the mechanical properties of trabecular bone is important in determining the fracture risk of human bones. Many uncertainty factors contribute to the dispersion of the estimated mechanical properties of trabecular bone. This study was undertaken in order to propose a computational scheme that will be able to predict the effective apparent elastic moduli of trabecular bone considering the uncertainties that are primarily caused by image-based modelling and trabecular stiffness orientation. The effect of image-based modelling which focused on the connectivity was also investigated. A stochastic multi-scale method using a first-order perturbation-based and asymptotic homogenisation theory was applied to formulate the stochastically apparent elastic properties of trabecular bone. The effective apparent elastic modulus was predicted with the introduction of a coefficient factor to represent the variation of bone characteristics due to inter-individual differences. The mean value of the predicted effective apparent Young's modulus in principal axis was found at approximately 460 MPa for respective 15.24% of bone volume fraction, and this is in good agreement with other experimental results. The proposed method may provide a reference for the reliable evaluation of the prediction of the apparent elastic properties of trabecular bone.     

In vivo characterization of the mechanical properties of human skin derived from MRI and indentation techniques

The human skin is an exceedingly complex and multi-layered material. This paper aims to introduce the application of the finite element analysis (FEA) to the in vivo characterization of the non-linear mechanical behaviour of three human skin layers. Indentation tests combined with magnetic resonance imaging (MRI) technique have been performed on the left dorsal forearm of a young man in order to reveal the mechanical behaviour of all skin layers. Using MRI images processing and a pre and post processor allows to make numerically individualized 2D model which consists of three skin layers and the muscles. FEA has been applied to simulate indentation tests. Neo-Hookean slightly compressible material model of two material constants (C₁₀, K) has been used to model the mechanical behaviour of the three skin layers and the muscles. The identification of material model parameters was done by applying Levenberg–Marquardt algorithm (LMA). Our methodology of identification provides a range of values for each constant. Range of values of different material properties of epidermis, dermis, hypodermis are respectively, C10_E = 0.12 ± 0.06 MPa, C10_D = 1.11 ± 0.09 MPa, C10_H = 0.42 ± 0.05 KPa, K _E = 5.45 ± 1.7 MPa, K _D = 29.6 ± 1,28 MPa, K _H = 36.0 ± O.9 KPa.     

Couple-stress moduli of a trabecular bone idealized as a 3D periodic cellular network

Trabecular bone is modeled as a cellular material with an idealized periodic structure made of open cubic cells, which is effectively orthotropic. We evaluate apparent couple-stress moduli of such a periodic material; apparent moduli refer to the moduli obtained using a domain smaller than a Representative Volume Element and they depend on boundary conditions. We conduct this analysis computationally (using ANSYS) by subjecting a unit cell of this periodic cellular material to either displacement or traction boundary conditions. Cell walls, representing bone tissue, and void space, representing bone marrow, are both modeled and they are assumed to be linear elastic. The applied loadings include a uniaxial extension (or uniaxial stress), a hydrostatic deformation (or hydrostatic stress) and a shear deformation (or shear stress) to evaluate the first stiffness (or compliance) tensor, and an applied curvature (or bending moment), a uniaxial twist (or torsion), and a triaxial twist (or triaxial torsion) to evaluate the second couple-stress stiffness (or compliance) tensor. Apparent couple-stress moduli are computed by equating the total strain energy stored in the unit cell with the energy of an equivalent homogeneous orthotropic couple-stress material for each applied loading. The moduli computed using displacement boundary conditions give upper bound, while those obtained using traction boundary conditions give lower bound on effective couple-stress moduli. These bounds are very wide due to a large mismatch in elastic moduli of bone tissue and bone marrow. These results are in agreement with our studies on composite materials with very stiff or very compliant inclusions.     

Microstructure and nanomechanical properties of single stalks from diatom Didymosphenia geminata and their change due to adsorption of selected metal ions

We present topographical and nanomechanical characterization of single Didymosphenia geminata stalk. We compared the samples before and after adsorption of metal ions from freshwater samples. Transmission electron microscopy studies of single stalk cross‐sections have shown three distinct layers and an additional thin extra coat on the external layer (called “EL”). Using scanning electron microscopy and atomic force microscopy (AFM), we found that topography of single stalks after ionic adsorption differed significantly from topography of pristine stalks. AFM nanoindentation studies in ambient conditions yielded elastic moduli of 214 ± 170 MPa for pristine stalks and 294 ± 108 MPa for stalks after ionic adsorption. Statistical tests showed that those results were significantly different. We conducted only preliminary comparisons between ionic adsorption of several stalks in air and in water. While the stalks with ions were on average stiffer than the pristine stalks in air, they became more compliant than the pristine stalks in water. We also heated the stalks and detected EL softening at 50°C ± 15°C. AFM nanoindentation in air on the softened samples yielded elastic moduli of 26 ± 9 MPa for pristine samples and 43 ± 22 MPa for stalks with absorbed metal ions. Substantial decrease of the EL elastic moduli after heating was expected. Significantly different elastic moduli for the samples after ionic adsorption in both cases (i.e., for heated and nonheated samples), as well as behavior of the stalks immersed in water, point to permanent structural EL changes due to ions.     

Agrobacterium-mediated transformation of embryogenic cell suspension cultures and plant regeneration in Lilium tenuifolium oriental × trumpet ‘Robina’

A method has been developed for embryogenic cell suspension cultures, plant regeneration and transformation of the important ornamental lily genotype (Lilium tenuifolium oriental × trumpet ‘Robina’). Bulb scales, filaments, ovaries and stem axis tissues were used as explants for callus induction in Murashige and Skoog (MS) medium with additions of growth regulators: picloram on its own, or in combination with 1-naphthaleneacetic acid (NAA), and thidiazuron (TDZ). The results show that the optimum medium for callus induction in bulb scale and filament tissue is MS + picloram 1.0 mg L^?1, and for the ovary, it is MS + picloram 1.5 mg L^?1. The stem axis had the highest rate (89.2 %) of callus induction with MS + NAA 2.2 mg L^?1 + TDZ 0.1 mg L^?1. The suspension cultures were established with the combination of NAA and TDZ with 2–5 mm cell clusters. These took a long time compared with suspension cultures established by picloram with 1–3 mm cell clusters. In three suspension cultures induced by picloram, the best callus from the point of view of proliferation and regeneration was derived from filaments. For plant regeneration, the growth rate of suspension cultures from the stem axis was higher than from the other three suspension culture induced by picloram. Vector pCAMBIA1301 with the β-glucuronidase (GUS) gene as reporter was transformed by Agrobacterium mediation into suspension cultures initiated from filament and stem axis material. After co-cultivation, the numbers of blue spots in material from the two sources were 26.8 ± 4.3 and 24.0 ± 4.7, respectively (difference not significant). Hygromycin-resistant callus was successfully regenerated into plantlets on plant growth regulator-free MS medium. Transgenic plants were also confirmed by the GUS histochemical assay, polymerase chain reaction.     

Effect of plant growth regulator combination and culture period on in vitro regeneration of spinach (Spinacia oleracea L.)

The objective of this study was to develop an efficient system for the regeneration of spinach plants (Spinacia oleracea L.) by investigating the factors influencing callus and shoot induction. All plant growth regulator (PGR) combinations tested induced callus with high frequency (73–100 %), and the combination of 5 μM α-naphthaleneacetic acid (NAA), 10 μM 6-benzyladenine (BA) and 0.1 μM gibberellic acid (GA₃) had the most significant effect on callus growth in term of weight (120.98 ± 22.56 mg). A high auxin-containing medium induced competent callus for shoot formation, while high cytokinin-containing media enhanced callus growth and made callus incompetent for shoot regeneration. Longer periods of callus induction in a high auxin-containing medium were required to form competent callus and led to a high regeneration capacity. The PGR combination shift from a high auxin to cytokinin ratio (ACR) to a low ACR resulted in highly efficient regeneration. Among the regeneration systems tested, the combination of 10 μM NAA and 0.3 μM GA₃ for callus induction for 6 weeks followed by 2 μM NAA and 5 μM BA resulted in the highest plant regeneration frequency (83.33 ± 6.43 %) and the highest number of plantlets per explant (7.93 ± 1.24). Somatic embryos at cotyledonary stage and plantlets were transferred to PGR-free medium to establish whole plants. Regenerated female plants grew well to maturity in the greenhouse (77.17 ± 9.80 %) and produced seeds (175.21 ± 28.01 firm seeds per plant).     

Anatomical variation of orthotropic elastic moduli of the proximal human tibia

The anatomical variation of orthotropic elastic moduli of the cancellous bone from three human proximal tibiae was investigated using an ultrasonic technique. With this technique, it was possible to measure three orthogonal elastic moduli and three shear moduli from cubic specimens of cancellous bone as small as 8 mm per side. Correlation with mechanical tensile testing has shown this technique to offer a precise measure of cancellous modulus (Eten = 0.94Eult + 144.6 MPa, r2 = 0.96, n = 34). The cancellous bone of the proximal tibia was found to be very inhomogeneous, with the axial modulus ranging between 340 and 3350 MPa. A course map is presented, showing measured Young's moduli as a function of anatomical position. The anisotropy of the cancellous bone, determined by the relative differences between the three orthogonal moduli, was shown to be relatively constant over the entire range of cancellous densities tested. The relationship between the axial elastic modulus and the apparent density was found to be approximately linear, as reported by others for proximal tibial cancellous bone.     

Indoleamines and calcium enhance somatic embryogenesis in <Emphasis Type="Italic">Coffea canephora</Emphasis> P ex Fr

Melatonin (MEL) and serotonin (SER) are important indoleamines that are involved in neural transmission in mammalian cells. They are also known to be present in various genera of plants. The role (s) of these indoleamines in plants are not well known. In this study, the effects of SER, MEL, calcium, and calcium ionophore (A23187), a calcium channel activator, on somatic embryogenesis in Coffea canephora have been investigated. Adding 100 μM of either SER or MEL to ½ strength Murashige and Skoog (MS) medium and 0.93 μM kinetin (KN) has resulted in enhanced induction of somatic embryogenesis, 85 ± 3 and 62 ± 6 embryos/callus, respectively. In the presence of either 5 mM calcium or 100 μM calcium ionophore A23187, number of somatic embryos/callus is also increased, with 56 ± 4 and 118 ± 10 somatic embryos/callus, respectively, compared to 25 ± 3 embryos/callus for control. The presence of 5 mM calcium chloride along with either 100 μM SER or 100 μM MEL, respectively, have also promoted somatic embryogenesis with induction of 105 ± 6 and 78 ± 2 somatic embryos/callus. While, addition of calcium ionophore A23187 along with either 100 μM SER or 100 μM MEL have produced 155 ± 12 or 135 ± 8 embryos/callus, respectively. In contrast, addition of such indoleamine inhibitors as 40 μM p-chlorophenylalanine (p-CPA), 20 μM fluoexitine hydrochloride (prozac), 1 mM verapamil hydrochloride (calcium channel blocker), and 1 mM ethylene glycol-bis (β-amino ethylether)-N, N, N′, N′-tetra acetic acid (EGTA) (a calcium chelator) individually, has inhibited induction of somatic embryos while reducing levels of endogenous pools of SER, MEL and indole-3-acetic acid (IAA) levels. Calcium imaging by laser scanning confocal microscopy (LSCM) has revealed high fluorescence intensity in callus treated with calcium and calcium ionophore A23187. Immunolocalization of SER in different tissues of C. canephora has revealed that it is localized in vascular tissues of stems, roots, and somatic embryos, as well as in endocarps (husks) of immature fruits.     

Estimation of the effective yield properties of human trabecular bone using nonlinear micro-finite element analyses

Micro-finite element (\(\upmu \)FE) analyses are often used to determine the apparent mechanical properties of trabecular bone volumes. Yet, these apparent properties depend strongly on the applied boundary conditions (BCs) for the limited size of volumes that can be obtained from human bones. To attenuate the influence of the BCs, we computed the yield properties of samples loaded via a surrounding layer of trabecular bone (“embedded configuration”). Thirteen cubic volumes (10.6 mm side length) were collected from \(\upmu \)CT reconstructions of human vertebrae and femora and converted into \(\upmu \)FE models. An isotropic elasto-plastic material model was chosen for bone tissue, and nonlinear \(\upmu \)FE analyses of six uniaxial, shear, and multi-axial load cases were simulated to determine the yield properties of a subregion (5.3 mm side length) of each volume. Three BCs were tested. Kinematic uniform BCs (KUBCs: each boundary node is constrained with uniform displacements) and periodicity-compatible mixed uniform BCs (PMUBCs: each boundary node is constrained with a uniform combination of displacements and tractions mimicking the periodic BCs for an orthotropic material) were directly applied to the subregions, while the embedded configuration was achieved by applying PMUBCs on the larger volumes instead. Yield stresses and strains, and element damage at yield were finally compared across BCs. Our findings indicate that yield strains do not depend on the BCs. However, KUBCs significantly overestimate yield stresses obtained in the embedded configuration (+43.1 ± 27.9%). PMUBCs underestimate (?10.0 ± 11.2%), but not significantly, yield stresses in the embedded situation. Similarly, KUBCs lead to higher damage levels than PMUBCs (+51.0 ± 16.9%) and embedded configurations (+48.4 ± 15.0%). PMUBCs are better suited for reproducing the loading conditions in subregions of the trabecular bone and deliver a fair estimation of their effective (asymptotic) yield properties.     

PHILOS钢板治疗老年肱骨近端冠状面骨折初探

目的:探讨采用PHILOS钢板治疗肱骨近端冠状面骨折手术治疗的早期临床疗效。方法:对2005年4月至2014年5月我院收治的9例肱骨近端冠状面骨折患者予以切开复位钢内固定治疗,采用DASH评分,生活质量评价量表(SF-36),Constant-Murley评分以及加利福尼亚洛杉矶大学肩关节评分(UCLA Score)对患者进行功能评价。结果:纳入患者平均年龄为63.5±3.2岁(53~82岁),男性2例,女性7例,根据Neer分型,单纯二部分骨折5例,二部分骨折伴肩关节脱位4例。术后随访12~22个月,平均14.2±3.2个月。9例患者均得到随访。所有患者肱骨近端骨折均愈合,骨折愈合时间12~18周,平均12.7±2.5周,末次随访时,7例无明显肩关节疼痛,2例有轻微疼痛,Constant评分平均87.0±4.2分;DASH评分平均20.9±2.5分,加州大学肩关节评分系统(UCLA)平均31.3±2.1;SF-36评分平均分,影像学结果显示:末次随访肱骨头高度平均丢失1.7±0.4 mm,颈干角度平均为126±13°。结论:采用切开复位钢板内固定对于肱骨近端冠状面骨折早期临床疗效良好,远期疗效有待进一步评价。     

Efectos del tratamiento con ácido zoledrónico en pacientes adultos con osteogénesis imperfecta

Background and objectiveOsteogenesis imperfecta (OI) is a genetic disorder that results in bone fragility. Several studies have demonstrated the effectiveness of bisphosphonate therapy. The aim of this study was to evaluate the effects of intravenous zoledronic acid on bone mineral density (BMD) and biochemical markers of bone turnover in adults with OI.Material and methodsWe carried out a prospective non-randomized study in patients with osteoporosis or severe osteopenia (T score <?2) related to OI and intolerance or contraindication to oral bisphosphonates. The patients were treated with a zoledronic acid infusion every 6 months. Densitometry was carried out annually. Calcium (Ca), phosphate (P), intact parathormone (PTH), 25 hydroxyvitamin D and biochemical markers of bone turnover [bone alkaline phosphatase (BAP), beta-cross-laps (CTX) and urinary deoxypyridoxine (DOP)] were measured every year. Adverse events and new fractures were registered.ResultsTen patients (2 men and 8 women) were treated. Treatment increased BMD measured in the lumbar spine after 24 (0.738±0.141 vs 0.788±0.144 g/cm²; p=0.048) and 36 months (0.720±0.139 vs 0.820±0.128; p=0.01). Significant increases in BMD were also observed after 24 months in the femoral neck (0.677±0.121 vs 0.703±0.122 g/cm²; p<0.016). Serum Ca, P, BAP and CTX concentrations remained unchanged. PTH concentrations increased and vitamin D concentrations decreased after 36 months of treatment. DOP excretion decreased significantly after 24 months. Seven patients had mild influenza-like symptoms occurring within the first 24 h after the first infusion. No severe adverse events were observed. None of the patients had new fractures.ConclusionZoledronic acid seems to be a safe and effective treatment option in adults with osteoporosis related to OI.     

New resource for the computation of cartilage biphasic material properties with the interpolant response surface method

Cartilage material properties are important for understanding joint function and diseases, but can be challenging to obtain. Three biphasic material properties (aggregate modulus, Poisson's ratio and permeability) can be determined using an analytical or finite element model combined with optimisation to find the material properties values that best reproduce an experimental creep curve. The purpose of this study was to develop an easy-to-use resource to determine biphasic cartilage material properties. A Cartilage Interpolant Response Surface was generated from interpolation of finite element simulations of creep indentation tests. Creep indentation tests were performed on five sites across a tibial plateau. A least-squares residual search of the Cartilage Interpolant Response Surface resulted in a best-fit curve for each experimental condition with corresponding material properties. These sites provided a representative range of aggregate moduli (0.48–1.58 MPa), Poisson's ratio (0.00–0.05) and permeability (1.7 × 10^? 15–5.4 × 10^? 15 m⁴/N s) values found in human cartilage. The resource is freely available from https://simtk.org/home/va-squish.     

不同植入物内固定治疗四肢创伤骨折后骨不连的临床对比研究

目的:探讨不同植入物内固定治疗四肢创伤骨折后骨不连的临床疗效。方法:选择我科2010年2月~2013年2月四肢创伤骨折后骨不连患者38例,按照随机数表法将38例患者随机分为两组,分别为LC-DCP组以及LCP组,每组各19例,观察两组患者的平均手术持续时间、骨折临床愈合时间、X线骨痂评分以及并发症。结果:LC-DCP组平均手术持续时间为(134.73±12.91)min,LCP组为(129.54±14.87)min,两组比较不存在统计学差异(P0.05)。LC-DCP组患者平均骨折临床愈合时间为(3.94±0.83)月,LCP组为(3.81±0.69)月,两组间不存在统计学显著性差异(P0.05)。LC-DCP组患者X线骨痂评价标准平均评分值为(2.73±0.51)分,LCP组为(2.86±0.49)分,两组间差异不存在统计学意义(P0.05)。结论:两种钢板联合植骨治疗四肢创伤骨折后骨不连均能够取得良好的治疗效果,均可以作为治疗四肢创伤骨折后骨不连患者的有效方法。     

Porcine bone grafts defatted by lipase: efficacy of defatting and assessment of cytocompatibility

Defatting is an important procedure for the preparation of bone grafts because lipids in bone grafts strongly influence the osteointegration. Lipases have been widely used in different fields. However, study on the application to defatting process for bone grafts preparation has never been found so far. In this study, bone samples were treated respectively by lipase, NaHCO₃/Na₂CO₃, acetone and deionized water. The lipids content of processed bone grafts was calculated in Soxhlet extractor method. Surface morphology of the bone grafts was observed under scanning electron microscope (SEM). DNA content of processed bone grafts was measured. Cytocompatibility was evaluated by co-culturing mouse preosteoblasts (MC3T3-E1) on defatted bone cubes. Proliferation rates of MC3T3-E1 were examined by cell counting kit-8 (CCK-8) assay. No statistically significant difference was found between lipids amount of bone processed by lipase (0.46 ± 0.16 %) and acetone (1.11 ± 0.13 %) (P > 0.05). Both of them were significantly lower than that in groups processed by Na₂CO₃/NaHCO₃ (3.46 ± 0.69 %) and deionized water (8.88 ± 0.18 %) (P = 0.000). Only cell debris were discovered over the surface of bone processed by lipase or acetone, while lipid droplets were observed on bone processed by Na₂CO₃/NaHCO₃ or water by SEM. The difference of DNA concentration between the bone processed by lipase (3.16 ± 0.81 ng/μl) and acetone (4.14 ± 0.40 ng/μl) is not statistically significant (P > 0.05). Both of them are significantly lower than that groups processed by Na₂CO₃/NaHCO₃ (5.22 ± 0.38 ng/μl) and water (7.88 ± 0.55 ng/μl) (P < 0.05). MC3T3-E1 cells maintained their characteristic spreading on the trabecular surfaces of bone processed by lipase. There were no statistically significant differences among absorbance of lipase, acetone groups in CCK-8 assay. The application of lipase to bone tissue defatting appears to be a very promising technique for bone grafts preparation.     

Development of an in vitro protocol for a difficult-to-propagate endemic Australian dryland sedge species Mesomelaena pseudostygia (Cyperaceae)

In vitro propagation for Mesomelaena pseudostygia a difficult-to-propagate dryland sedge species (Cyperaceae) endemic to Western Australia is described. Multiple avenues to in vitro propagation were investigated: shoot culture, organogenesis and somatic embryogenesis, with zygotic embryos as initiation material. The highest multiplication rate for shoots was 3.4?±?1.0 after 6 wk on basal medium (1/2 strength Murashige and Skoog) with 2.5 μM kinetin and 0.5 μM 6-benzylaminopurine. Shoots achieved peak rooting (83%) following a pulse treatment on basal medium containing 10 μM indolebutyric acid and 2 μM α-naphthaleneacetic acid for 7 wk, followed by transfer to medium (without growth regulators) for a further 7 wk. Alternatively, in vitro grown shoots were pulse treated on basal medium with both 100 μM indolebutyric acid and 20 μM α-naphthaleneacetic acid for 1 wk then placed in Rockwool plugs (under propagation house conditions) for another 7 wk resulting in 63% root induction. Rooted plantlets were also successfully transferred to potting mixture either in Rockwool plugs or bare rooted and maintained in propagation house conditions with ≥95% survival after 7 wk. These results indicate that micropropagation of M. pseudostygia is feasible for small to medium scale restoration purposes. The highest frequency of callus induction was from cultured zygotic embryos on basal medium with 5 μM α-naphthaleneacetic acid, whereas 2,4-dichlorophenoxacetic acid (2 or 5 μM) produced the largest callus sizes. A low frequency of shoot regeneration occurred in zygotic callus tissues in basal medium treatments containing cytokinin (kinetin or thidiazuron at 1 μM). A small proportion (<20%) of zygotic embryo callus explants from 2,4-dichlorophenoxyacetic acid treatments were found to be embryogenic, firstly developing embryo-like structures after 2 wk on basal medium (minus plant growth hormones), that continued to develop with approximately one in twenty germinating after a further 4 wk on basal medium to form small plantlets. Further optimisation is needed to improve somatic embryogenesis efficiency for mass propagation.     

改良阶梯式截骨法矫正儿童创伤后肘内翻畸形

目的:探讨采用肱骨髁上改良阶梯式截骨联合钢板等内固定治疗儿童肘内翻畸形的临床疗效。方法:回顾性研究我科自2012年1月~2014年12月收治的14例肘内翻畸形患者,其中,男10例/女4例,年龄6~14岁,平均10.3岁,右侧9例/左侧5例。所有病例均有明确的伸直型肱骨髁上骨折病史,在创伤后约1.7年(1~4.5年)行改良阶梯式截骨。通过测量手术前后提携角及肘关节活动度,并依据Flynn临床肘关节功能评定标准对患肢功能进行评价。结果:本组患者术后均获得随访,随访时间12~26个月,平均17.4±2.7个月,肱骨截骨处达到骨性愈合的时间为2.5~4个月(平均2.9±0.6个月),术后畸形矫正良好,获得5.2±1.7°提携角。术后关节活动范围-0.7±1.6~134.5±2.4°,与术前相比,伸展活动的差异无统计学意义(t=0.871,P0.05);而屈曲活动改善明显,差异有统计学意义(t=18.819,P0.01)。末次随访时截骨纠正角度丢失1.4±0.8°。根据Flynn肘关节功能评定标准:优11例/良2例/可1例,优良率92.86%。均无感染、外髁突出、过度肥厚增生的术后瘢痕、血管神经损伤、关节不稳等并发症。结论:本研究针对创伤后儿童肘内翻畸形的手术疗效进行随访,发现改良阶梯式截骨的手术操作相对简单,矫形效果满意,能早期恢复肘关节功能且畸形复发率低,是一种美容效果较好的治疗肘内翻的截骨方式。     

Effects of damage on the orthotropic material symmetry of bovine tibial trabecular bone

The macroscopic mechanical properties of trabecular bone can be predicted by its architecture using theoretical relationships between the elastic and architectural properties. Microdamage caused by overloading or fatigue decreases the apparent elastic moduli of trabecular bone requiring these relationships to be modified to predict the damaged elastic properties. In the case of isotropic damage, the apparent level elastic properties could be determined by multiplying all of the elastic constants by a single scalar factor. If the damage is anisotropic, the elastic constants may change by differing factors and the material coordinate system could become misaligned with the fabric coordinate system. High-resolution finite element models were used to simulate damage overloading on seven trabecular bone specimens subjected to pure shear strain in two planes. Comparison of the apparent elastic moduli of the specimens before and after damage showed that the reduction of the elastic moduli was anisotropic. This suggests that the microdamage within the specimens was inhomogeneous. However, after damage the specimens exhibited nearly orthotropic material symmetry as they did before damage. Changes in the orientation of the orthotropic material coordinate system were also small and occurred primarily in the transverse plane. Thus, while damage in trabecular bone is anisotropic, the material coordinate system remains aligned with the fabric tensor.     

Current and future distributions of Espeletiinae (Asteraceae) in the Venezuelan Andes based on statistical downscaling of climatic variables and niche modelling

ABSTRACT

Background: Páramos are the high-elevation ecosystems of the humid tropical Andes, characterised by the presence of giant rosettes of the Espeletiinae subtribe (Asteraceae). Forecasted climate change is likely to reduce the extent of the area climatically suitable/occupied currently by Espeletiinae and their elevation distribution patterns.

Aims: The aim of this study was to estimate the potential impacts of forecasted climate change on the geographic distribution (extent of area and elevation distribution patterns) of 28 species of Espeletiinae that have been recorded in the Cordillera de Mérida, Venezuela.

Methods: Six bioclimatic variables, downscaled to a 90 m × 90 m cell size, were used to construct species distribution models (SDM) for the 28 species to model their current and likely future distribution (2070) by using two general circulation models and four representative concentration pathways (RCP).

Results: Nine species were estimated to have potential distribution over less than 1000 km² and five over less than 500 km², in current climatic conditions. Fifteen and eight species had elevation spans narrower than 1000 m and 500 m, respectively. No significant differences in modelled areas or spans were detected between north, central and south sections of the Cordillera de Mérida. Mean ± SE future reduction in the extent of area climatically suitable were estimated between 51.3% ± 6.3% (RCP2.6) and 78.1% ± 5.3% (RCP8.5), coupled with upward range retreat of between 277.8 m ± 27.4 m (RCP2.6) and 762.5 m ± 59.8 m (RCP8.5).

Conclusions: Our study predicts large reductions in modelled area and important upward shifts in the distribution of Venezuelan Espeletiinae by 2070 compared to their current distribution.