肩袖撕裂修补术后腱骨愈合的研究进展

肩袖撕裂通常发生在肩袖肌腱的附着点,这些肌腱连接着肱骨和肩胛骨,当这些肌腱受到损伤时,会导致肩关节的稳定性下降、活动受限以及剧烈的疼痛。肩袖撕裂的原因较多,包括外伤、慢性劳损、退行性病变等。对于肩袖撕裂的治疗,关节镜下修补术已成为主流方法,这种手术具有创伤小、恢复快、并发症少等优点,在临床上得到了广泛应用。肩袖撕裂修补术后仍具有较高的再撕裂风险,原因是腱骨界面未能恢复成原有的组织结构,并且形成了瘢痕,使得生物力学结构处于失衡的状态,从而增加了再撕裂的风险。本文对影响肩袖撕裂修补术后腱骨愈合的相关因素和促进腱骨愈合的相关研究进展进行如下综述。

加强生物实验教学活动促进新课程教学改革

本文根据成都市各中学生物实验教学改革现状,主要探讨了如何提高和培养学生的生物实践活动兴趣,构建生物实验的生物学理论支架培养学生的自主实践能力和快乐教育法提高生物实验设计能力等理论问题,以加强生物实验教学活动促进新课程教学改革。

Esophageal tissue engineering:A new approach for esophageal replacement

A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently complicated by stenosis and other problems.Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function.We review the literature of esophageal tissue engineering,discuss its implications,compare the methodologies that have been employed and suggest possible directions for the future.Medline,Embase,the Cochrane Library,National Research Register and ClinicalTrials.gov databases were searched with the following search terms:stem cell and esophagus,esophageal replacement,esophageal tissue engineering,esophageal substitution.Reference lists of papers identified were also examined and experts in this field contacted for further information.All full-text articles in English of all potentially relevant abstracts were reviewed.Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation.When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality.Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration,whilst omental wrapping to induce vascularization of the construct has an uncertain benefit.Decellularized matrices have been recently suggested as the optimal choice for scaffolds,but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution.Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement.Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus.Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease,important barriers remain that need to be addressed.

Computational Fluid Dynamics Simulation on Biomedical Stent Design

The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensus that the stent implant may change the artery wall shear stress distribution and hence lead to the restenosis process. Computational fluid dynamics （CFD） has been widely used to analyze hemodynamics in stented arteries. In this paper, two CFD models （the axisymmetric model and the 3-D stent model） were developed to investigate the effects of strut geometry and blood rheology on the intra-stent hemodynamics. The velocity profile, flow recirculation, and wall shear stress distribution of various stent strut geometries were studied. Results show strong correlations between the intra-stent hemodynamics and strut geometry. The intra-stent blood flow is very sensitive to the strut height and fillet size. A round strut with a large fillet size shows 36% and 34% reductions in key parameters evaluating the restenosis risk for the axisymmetric model and the 3-D stent model, respectively. This suggests that electrochemical polishing, a surface-improving process during stent manufacturing, strongly influences the hemodynamic behavior in stented arteries and should be controlled precisely in order to achieve the best clinical outcome. Rheological effects on the wall shear stress are minor in both axisymmetric and 3-D stent models for the vessel diameter of 4 mm, with Newtonian flow simulation tending to give more conservative estimates ofrestenosis risk. Therefore, it is reasonable to simulate the blood flow as a Newtonian flow in stented arteries using the simpler axisymmetric model. These findings will provide great insights for stent design optimization for potential restenosis improvement.

Cell Area and Strut Distribution Changes of Bent Coronary Stents:A Finite Element Analysis

Coronary stents are metal coils or mesh tubes delivered to blocked vessels through catheters, whic Recently, special drugs h are expanded by balloons to reopen and scaffold target vessels. are carried by stents （drug-eluting stents） to further reduce instent restenosis rate after stenting procedure. However, continual study on biomechanical characteristics of stents is necessary provide a more suitable drug loading for better interactions between stents and tissue, or to platform for drug-eluting stents. The purpose of this paper is to show how finite element methods can be used to study cell area and strut distribution changes of bent coronary stents. A same bending deformation was applied to two commercial coronary stent models by a rigid curved vessel. Results show that the stent design influenced the changes of cell area and strut distribution under bending situation. The stent with links had more cell area changes at outer curvature, and the stent with peak-peak （ 〉 〈 ） strut design could have strut contact and overlapping at inner curvature. In conclusion, this finite element method can be used to study and compare cell area and strut distribution changes of bent stents, and to provide a convenient tool for designers in testing and improving biomechanical characteristics of new stents.

Advancements in three-dimensional titanium alloy mesh scaffolds fabricated by electron beam melting for biomedical devices: mechanical and biological aspects

We elucidate here the process-structure-property relationships in three-dimensional（3 D） implantable titanium alloy biomaterials processed by electron beam melting（EBM） that is based on the principle of additive manufacturing. The conventional methods for processing of biomedical devices including freeze casting and sintering are limited because of the difficulties in adaptation at the host site and difference in the micro/macrostructure, mechanical, and physical properties with the host tissue. In this regard, EBM has a unique advantage of processing patient-specific complex designs, which can be either obtained from the computed tomography（CT） scan of the defect site or through a computeraided design（CAD） program. This review introduces and summarizes the evolution and underlying reasons that have motivated 3 D printing of scaffolds for tissue regeneration.The overview comprises of two parts for obtaining ultimate functionalities. The first part focuses on obtaining the ultimate functionalities in terms of mechanical properties of 3 D titanium alloy scaffolds fabricated by EBM with different characteristics based on design, unit cell, processing parameters, scan speed, porosity, and heat treatment. The second part focuses on the advancement of enhancing biological responses of these 3 D scaffolds and the influence of surface modification on cell-material interactions. The overview concludes with a discussion on the clinical trials of these 3 D porous scaffolds illustrating their potential in meeting the current needs of the biomedical industry.

Microscale methods to assemble mammalian cells into tissue-like structures

Different cell types make up tissues and organs hierarchically and communicate within a complex, three-dimensional (3D) en- vironment. The in vitro recapitulation of tissue-like structures is meaningful, not only for fundamental cell biology research, but also for tissue engineering (TE). Currently, TE research adopts either the top-down or bottom-up approach. The top-down approach involves defining the macroscopic tissue features using biomaterial scaffolds and seeding cells into these scaffolds. Conversely, the bottom-up approach aims at crafting small tissue building blocks with precision-engineered structural and functional microscale features, using physical and/or chemical approaches. The bottom-up strategy takes advantage of the repeating structural and functional units that facilitate cell-cell interactions and cultures multiple cells together as a functional unit of tissue. In this review, we focus on currently available microscale methods that can control mammalian cells to assemble into 3D tissue-like structures.