Mechanism design and analysis of a simple leg-sliding rehabilitation equipment / 中国康复理论与实践

ObjectiveTo design a simple leg-sliding rehabilitation equipment for patients with lower limb dysfunction who need to exercise their leg muscles in bed at the early stage of rehabilitation. MethodsThe mechanism scheme was designed using the crank slider transmission system. The kinematic model was established and the structural dimensions were determined according to the human joint mobility, analysis and verification were then implemented; and the strutural strength of the machanism was verified, and based on the analysis, a protype was built to verify the feasibility of proposed scheme. ResultsThe range of joint activities of the proposed mechanism was in line with the normal human joint activities, the structural strength met the requirements, the prototype operated smoothly, and the actual running speed was basically consistent with the theoretical planning speed. ConclusionThis design could meet the needs of rehabilitation training for bedridden patients with lower limb dysfunction at the early stage of rehabilitation. It has the advantages of small size and light weight, which provides reference value for promoting the development of miniaturized and lightweight lower extremity rehabilitation equipment.

Research on Self-tapping Performance Test of Self-tapping Bone Screws / 中国医疗器械杂志

OBJECTIVE@#To study the self-tapping performance test method of self-tapping bone screws based on the YY/T 1505 standard.@*METHODS@#With reference to the method of YY/T 1505, various factors affecting the self-tapping force test was optimised, and the self-tapping force judgment method was improved.@*RESULTS@#The experimental results showed that the self-tapping force obtained by the improved self-tapping force judgment method has good repeatability and high stability of the experimental data. At the same time, the test results of other influencing factors indicated that the manufacturer should fully consider the test material and the size of the pre-drilled hole.@*CONCLUSIONS@#An improved method for judging the self-tapping force is helpful for the repeatability and stability of the test data. This study has certain significance referring to the self-tapping performance test of self-tapping bone screws.

Synthesis of ureasil-polyether film forming materials by using environmentally friendly solvent

Organic inorganic hybrids present several advantages as drug release systems, such as: high flexibility, high mechanical and thermal resistance, transparency, and low water solubility. These hybrids are synthesized through a chemical route named sol-gel that usually uses as solvente tetrahydrofuran (THF). Objetives: To develop film formers from hybrid materials replacing THF with ethanol, a less toxic solvent for skin application and for the environment. Methods: Four polymers were used: two based on polyethylene oxide (PEO) with molecular weight of 500 and 1900 g mol-1 and two based on polypropylene oxide (PPO), with molecular weight of 400 and 2000 g mol-1. The structural analysis was performed by FTIR, 1H-NMR and 29Si-NMR, and the thermal-mechanical analysis by DSC and TG-DTA. Results: The results of the thermo-mechanical analysis revealed that the solvent replacement did not affect the thermal stability and flexibility of the di-ureasil hybrid. Conclusions: Structural characterization confirmed the formation of hybrids both in THF and in ethanol. Therefore, ethanol is an excellent solvent for the synthesis of these hybrid matrices, since it allows obtaining the same material without changing its characteristics, with some advantages, however, over THF. Furthermore, this paper describes the efficiency of ethanol as a solvent, which is environmentally friendly, to replace THF in the physical-chemical characteristics of these filming former materials.

Impacted molar upright with self-made helical spring / 华西口腔医学杂志

With a case of mesial impaction of maxillary first and second molar, the mechanical analysis and clinical applications of a self-made helical spring for the uprighting treatment of mesial impacted molars was introduced.

Stability of the femoral neck and internal fixation with bone cement and steel plate after curettage for benign proximal femoral lesions / 中国组织工程研究

BACKGROUND: For benign bone tumor patients, the life cycle is long. To reduce the incidence of complications and improve the quality of life after surgery through surgery is the common goal of physicians. The quality of life of patients can be increased through discussing the operation mode and prognosis of benign tumor patients, choosing the reasonable operation mode, predicting and reducing the risk of secondary fracture. OBJECTIVE: To analyze the femoral neck force after different surgical methods using finite element technique in the analysis of benign proximal femoral lesions, and to assess the stability of the femoral neck and the risk of fracture after different surgical procedures for cases with a wide range of lesions. METHODS: According to preoperative CT data of lesion sites in 10 subjects with benign tumor of proximal femur, three-dimensional model of internal fixation with bone cement and steel plate after focal curettage (group A) and three-dimensional model of treating with bone cement after focal curettage (group B) were set in this study. Finite element technique was used to simulate the maximum force of the femoral neck when walking. The stress peaks of the femoral neck were compared after surgery between the two groups. The risk of fracture at this location was assessed. Patients signed the informed consent. This study was approved by the Ethics Committee of Chengde Medical College. RESULTS AND CONCLUSION: (1) The stress was significantly lower in the group A than in the group B (P=0.007 < 0.05). (2) The local stress of the model was reasonable in the group A. Ten patients were operated with the protocol of the group A. An additional 17 patients with proximal femur benign lesions who met the requirements but refused to enter the finite element experiment were treated with the surgical program of the group A. (3) The patients were followed up for 14-42 months. During the follow-up, no new fracture was found in the operation area, and the internal fixation device was firm without fracture. At 12 months postoperatively, the mean Musculoskeletal Tumor Society score of all patients was (26.12±2.28). (4) The finite element technology for simulating the stress evaluation and postoperative follow-up verified that the treatment of proximal femur benign tumor with bone cement and steel plate internal fixation after curettage is more reasonable and effective. The scheme can effectively reduce the risk of secondary fracture and enhance the stability in the surgical area.

Mechanical Analysis of Single Shoulder Airbag External Fixator for Clavicle Fractures / 医用生物力学

Objective In view of the problems existing in traditional external fixator, to invent a novel single shoulder airbag external fixator, and evaluate the reductional stretch force produced by it. Methods The three-dimensional finite element model of human clavicle was established. The loading conditions of the single shoulder airbag external fixator and the reductional stretch force produced by the external fixator were analyzed comprehensively and systematically. The actual loading conditions of the single shoulder airbag external fixator and the traditional eight-figure bandage external fixator were compared and analyzed by experiment. Results Reductional stretch force produced by the single shoulder airbag external fixator was more uniform and larger than that produced by traditional external fixator, and could be adjusted by the patient himself. Conclusions The force and the loading method of the single shoulder airbag external fixator on the shoulder were more favorable for the stretched reduction of clavicle fractures and maintaining the position of clavicle fractures, and it could make the patients with clavicle fractures more comfortable.

Topology Optimization of Bionic Porous Structure Based on Biomechanical Properties of Trabecular Bone / 医用生物力学

Objective Based on structure of animal trabecular bone, implants with porous structure were designed to describe mechanical properties of trabecular structure and explain significance of bionic trabecular porous implants in clinical treatment. Methods Based on anisotropic mechanical properties of animal trabecular bone, a porous structure was designed using the topology optimization method. The principles of partition and block reconstruction were first proposed according to bone function theory. The trabecular structure was then reconstructed based on micro-CT images. The boundary constraint and external load were applied on this model according to the respective-volume-element (RVE) method. Taking the solved mechanical properties as objective functions of optimization, the porous structure design and optimization were conducted using the variable density method and the homogenization method. Results The trabecular bone possessed the anisotropic mechanical properties. It was found that the volume fraction showed an increasing trend from the edge to the middle across the same section of trabecular bone. But there was no obvious regular pattern in Poisson’s ratio, which was evenly distributed in the range between 0.17 and 0.30. As to the values of elastic modulus and shear modulus, they were both significantly higher in the main pressure position compared with those in the other positions. After topography optimization based on these mechanical properties, the Poisson’s ratio of the optimized model was in the same range as the animal trabecular bone. The elastic modulus error was less than 14%， with the minimum being only 3%. In addition, the shear modulus error was below 8%， which ultimately complied with criteria of the original goal. Conclusions The designed porous structure based on topology optimization had the same anisotropic characteristics as animal trabecular bone, while reducing the stress concentration phenomenon, which could achieve the specific design for porous structure, thus providing a reasonable and effective method for clinical porous implants.

Study of the influence of pigments in the polymerization and mechanical performance of commercial dental composites / Estudo sobre a influência dos pigmentos na polimerização e no desempenho mecânico dos compósitos dentais comerciais

Objective: The aim of this study was to analyze the influence of the amount of shade pigment and opacifying components inthe polymerization and mechanical properties in two brands of Brazilian dental resin composites. Material and Methods: Master Fill microhybrid resin for enamel (colorless and shades A2, A4), and Opallis for enamel and dentine, both shades A2. Thecomposite resins were photopolymerized by a LED device at 19.7 J. The mechanical properties were obtained through flexuralresistance (FR), compression strength (CS) and Vickers microhardness (VM); the degree of conversion (DC) was obtainedby FTIR and translucence was obtained by sphere espectrometer. Conclusion: The analysis indicated that resin with more colorpigments (MA4) or more opacity components (ODA2) hadlow polymerization and poor mechanical properties than clearer(M) or more translucent (OEA2) resins, indicating that betterperformance can be obtained by increasing the radiation dose.

Objetivo: O objetivo deste estudo era analisar a influênciada quantidade de pigmentos de cor e de componentes opacificantesna polimerização e nas propriedades mecânicas em duasmarcas Brasileiras de resinas compostas dentárias. Material e Métodos: Resina Master Fill, microhíbrida, para esmalte (incolore nas cores A2 e A4) e Opallis para esmalte e dentina, ambas na cor A2. As resinas foram fotoativadas por um aparelho diodo emissor de luz (LED) a 19.7 J. As propriedades mecânicas foram obtidas por resistência flexural, força de compressão, microdureza Vickers; o grau de conversão foi obtido por FTIR e a translucidez foi obtida por meio do Espectrômetro de Esfera. Conclusões: As análises indicaram que resinas com mais pigmentos decor (MA4) ou mais componentes opacificantes (ODA2) mostrarambaixa polimerização e pobre qualidade mecânica quandocomparadas às mais claras e/ou mais translúcidas, indicando que a dose de irradiação deve ser aumentada para obter melhor performance.