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Objective:To investigate the biomechanical properties of cannulated screws fixation in a configuration of "axial compression and lateral buttress" in the treatment of Pauwels type Ⅱ femoral neck fractures.Methods:Ten specimens of Sawbones artificial femur were first made into models of type Ⅱ femoral neck fracture with a Pauwells angle of 50° and then randomized into 2 equal groups ( n=5). The specimens in the experimental group were subjected to fixation with cannulated screws in a configuration of "axial compression and lateral buttress" in which the axial screw was 8.5 mm in diameter and the lateral screw 6.5 mm in diameter. The specimens in the control group were subjected to conventional fixation with cannulated screws in a configuration of "inverted triangle and parallel compression" in which the 3 screws was 7.3 mm in diameter. Finally, the specimens were placed onto a biomechanical testing machine to determine the parameters of static axial stiffness, displacement under 60 to 600 N load for 5,000 cycles, ultimate load and ultimate stiffness in turn. The 2 groups were compared to find out their differences. Results:The static axial stiffness was (1,492.00 ± 87.86) N/mm, significantly higher than that in the control group [(1,200.22 ± 228.06) N/mm] ( P<0.05). There was no significant difference between the 2 groups in the cyclic load displacement [(0.44 ± 0.01) mm versus (0.57 ± 0.17) mm] ( P>0.05), but the experimental group showed a lower trend. The ultimate load and ultimate stiffness were (4,292.61 ± 804.29) N and (1,623.55 ± 180.94) N/mm in the experimental group and (4,383.64 ± 1,423.24) N and (1,433.77 ± 289.93) N/mm in the control group, showing no significant difference between the 2 groups ( P>0.05). Conclusion:In the treatment of Pauwels type Ⅱ femoral neck fractures, fixation with cannulated screws in a configuration of "axial compression and lateral buttress" may exhibit better biomechanical properties than that in a conventional configuration of "inverted triangle" .
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Objective To investigate the pathological mechanism of spinal injury by axial compression experiment on animal spine, so as to provide references for the treatment, prevention and research of spinal injury. Methods The biomechanical study of rabbit spine segments was performed by axial segment compression experiment. The compression process was recorded and strain analysis was performed by digital image correlation (DIC) technology. Results From the top to the bottom of the spine, the ultimate load and bearing capacity of the segment increased continuously; the average limit load of the corresponding single vertebral body was significantly larger than the segment; the strain of the intervertebral disc in the horizontal and vertical directions was significantly larger than that of the upper and lower vertebral bodies. Conclusions In the process of spine compression, the bearing capacity of the intervertebral disc should be taken into account and the injury of spinal segments is mainly manifested as abnormality of the intervertebral disc. The research findings contribute to the prevention and treatment of spinal compression fractures, as well as the design of related therapeutic instruments and assistive devices.
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BACKGROUND: The double-rod of bridge-link type combined internal fixation system belongs to eccentric fixation, which may lead to the weakening of longitudinal fixation and the decrease of transverse anti-torsion after operation. OBJECTIVE: To compare the biomechanical characteristics of bridge-link type combined internal fixation system with mixed-rod and double-rod in the treatment of femoral and tibial fractures. METHODS: Twenty human long bone diaphysis models were made by 40 short polyformaldehyde materials. Of these, 10 were fixed by mixed-rod, and the rest with bridge-link type combined internal fixation system. Axial compression tests and radial torsion tests were carried out (five models were selected from each group). The changes of axial compression forces and displacements and transverse torque and angle were observed. The maximum load was recorded when the curve had a break point or in a horizontal state, and then the yield load was calculated. RESULTS AND CONCLUSION: (1) When the axial compression load was
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Fraturas ósseas podem ser corrigidas com a utilização de fixadores esqueléticos externos (FEE), método de estabilização bastante comum. Para tanto, têm-se utilizado barras conectoras de polimetilmetacrilato (PMMA) sem critério de diâmetro, as quais podem quebrar, se ficarem muito delgadas, ou ocasionar incômodo, quando muito pesadas e volumosas. O objetivo deste trabalho foi testar, por meio de ensaio biomecânico de compressão axial e flexão, qual é o diâmetro ideal da barra conectora de PMMA, correlacionado com o diâmetro ósseo para utilização em FEE tipo Ia. Utilizaram-se 24 úmeros para se realizarem medidas de comprimento, diâmetro, circunferência e ensaios biomecânicos. Após, foram confeccionadas barras de 1,5 vezes a média do diâmetro ósseo (grupo I), do mesmo diâmetro ósseo (grupo II) e de 0,5 vezes o diâmetro (grupo III). Com os resultados obtidos ao se compararem os valores dos ossos com os dos grupos II e III, verificou-se que as barras conectoras do grupo II mostraram-se mais resistentes do que o tecido ósseo no ensaio de compressão. No ensaio de flexão, os ossos resistiram mais quando comparados aos grupos II e III, sendo 4,3 vezes mais resistentes do que o grupo III nesse mesmo ensaio mecânico. Os resultados permitem um direcionamento para confecção de barras considerando-se o diâmetro ósseo como referência.(AU)
Bone fractures can be corrected from external skeletal fixators (ESF) in a fairly common internal stabilization method, in which connector bars polymethylmethacrylate (PMMA) is used. PMMA is used without criterion of diameter, and it can break if it is too thin or too heavy. It can be uncomfortable when bulky. The aim of this study was to test, through biomechanical axial compression and bending which is the ideal connector bar diameter PMMA, correlated to bone diameter for use in type Ia ESF. Twenty-four humerus were used to make measurements of length, diameter, circumference, and biomechanical testing. After the bars confected with 1.5 times the average diameter of the bone (group I), the same diameter (group II) and 0.5 times the diameter of the bone (group III). With the obtained results, using GII and GIII results, it was observed that the connector bars in group II were more resistant than the bones in the compression test. In the bending test, the bones resisted flexion strength when compared to group III and the group II was 4.3 times more resistant than group III in the same mechanical test. The results allow a direction for making bars considering bone diameter as a reference.(AU)
Subject(s)
Animals , Fracture Fixation/statistics & numerical data , Fractures, Compression/veterinary , Swine/injuries , Biomechanical Phenomena , Polymethyl MethacrylateABSTRACT
Abstract Introduction Biomechanical assessment of trabecular bone microarchitecture contributes to the evaluation of fractures risk associated with osteoporosis and plays a crucial role in planning preventive strategies. One of the most widely clinical technics used for osteoporosis diagnosis by health professionals is bone dual-energy X-ray absorptiometry (DEXA). However, doubts about its accuracy motivate the introduction of congruent technical analysis such as calcaneal ultrasonometry (Quantitative Ultrasonometry - QUS). Methods Correlations between Bone Quality Index (BQI), determined by calcaneal ultrasonometry of thirty (30) individuals classified as normal, osteopenic and osteoporotic, and elastic modulus (E) and ultimate compressive strength (UCS) from axial compression tests of ninety (90) proof bodies from human vertebrae trabecular bone, which were extracted from cadavers in the twelfth thoracic region (T12), first and fourth lumbar (L1 and L4). Results Analysis of variance (ANOVA) showed significant differences for E (p = 0.001), for UCS (p = 0.0001) and BQI. Spearman's rank correlation coefficient (rho) between BQI and E (r = 0.499) and BQI and UCS (r = 0.508) were moderate. Discussion Calcaneal ultrasonometry technique allowed a moderate estimate of bone mechanical strength and fracture risk associated with osteoporosis in human vertebrae.
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This article was aimed to study the chemical constituents in groups of effective components extracted from Xiaoxuming Decoction. Twelve compounds were isolated and purified by dynamic axial compression column chromatography. Their chemical structures were identified by spectral analysis. The results showed that twelve compounds were isolated and identified as octacosanoic acid(1), cetanol(2), oroxylin A(3), wogonin(4), baicalein(5), tetrandrine(6), fangchinoline(7), wogonoside(8), baicalin(9), paeoniflorin(10), amygdalin(11), manntol(12). It was concluded that all compounds were isolated from this compound prescription for the first time.
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Objective To evaluate the biomechanical advantages of medial support screws (MSSs) in locking proximal humeral plate for treating proximal humerus fractures. Methods Thirty synthetic left humeri were randomly divided into 3 groups to establish the fracture models. Group A was fixed with a locking proximal humerus plate with medial cortical support, but without MSSs; group B was fixed with 3 MSSs, but without medial cortical support; group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsion, shear stiffness and failure tests were applied on the specimens of the three groups. Results For axial compression tests, the maximum load of group A, B, C was (240.88±19.13), (169.04±19.26), (128.58±17.53) N, respectively; the axial stiffness of group A, B, C was (424.4±101.2), (230.7±40.54), (147.0±29.2) N/mm, respectively, showing significant differences (P0.05). For shear stiffness tests, the maximum load of group A, B, C was (444.71±20.87), (228.79±28.95), (188.73±26.15) N, respectively; the shear stiffness of group A, B, C was (70.0± 54.4), (183.89±29.64), (140.2±32.1) N/mm, respectively, showing significant differences (P0.05). Conclusions Using three MSSs in locking plate for proximal humerus fractures shows optimal biomechanical properties, as compared to the situation without restoration of the medial column support. The reconstruction of the medial cortical support or MSSs for proximal humerus fractures helps to enhance the mechanical stability of the humeral head and prevent failure after internal fixation.
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Objective To explore the stability of unilateral external fixator for tibial fracture in its middle in condition of different distribution and number of screws. Methods The experiment model was made when eighteen human corpse tibial transverse fractures had been fixated with unilateral external fixation, which were divided into six groups. In each group, resistance fragments were adhered to be close to the transverse tibial fracture and near the screw-bone interface(SBI), including three screw distribution models, which were well distributed, close to and far off the fracture site distribution. Each model had also been accomplished according to the conditions of four and six screws before compression load of the same magnitude, the same direction and the same loading position. This method was used to observed the values of strain of SBI and axial displacement at the fracture site at grade load. Results ① Under compression condition, the models displacements and the force at Y-axial were the smallest when screw distribution was even in four or six screws and much better than those of four screws. ② The stability at the condition of six screws was stronger than that of four screws. Conclusion The even distribution of four screws is reasonable when tibial fractures are treated with unilateral external fixation, and six screws can be choosen if conditions permit.