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@#ObjectiveTo evaluate the strain of the weight-bearing metatarsal bone. Methods6 fresh-frozen cadaveric lower extremities were dissected to expose the dorsal aspect of metatarsal. Bone segments were clarified for adherence of strain-gauges while feet kept intact. Then vertical downward axial load was exerted to distal tibia at a 2 mm/min velocity, from 0 N to 1200 N with one minute interval of 200 N leveled loading augment each for sampling. Superficial strain of the metatarsal was measured by resistance strainmeter methods. ResultsThe strain increased gradually with axial loading, and compress force was always found at every marked bone. The strain of every marked bone was significantly different at the same loading (P<0.05). As to the strain of the middle of the metatarsal, the sequence was the second metatarsal＞the third metatarsal＞the fourth metatarsal＞the first metatarsal＞the fifth metatarsal. As to the strain of the second metatarsal, the sequence was the middle＞the neck＞the base. ConclusionThe peak strain was found at the middle of the second and third metatarsal with axial loading, which prompts the stress fractures of the second and third metatarsal are most common, especially the middle of the second metatarsal.
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To provide a digital simulation platform for foot-ankle biomechanics research, a 3-D finite element model was established through helical CT images under the principle of RE (reverse engineering) and meshed in FEM software. In the process of modeling cartilage, ligaments, tendons and plantar soft tissue, many anatomic data and results of cadaver specimen experiment were referenced; LINE elements and SHELL elements were used skillfully to simplify the model and resemble the physiological state. The model was then validated by specimen experimentation, which was done on seven fresh cadaver foot specimens, and digital speckle correlation method (DSCM) was used to measure their displacements. Upon the comparison with experimentation and others models, this study also testified that the model, of which the plantar fascia is linked to the heads of metatarsus, is more reasonable to clinical application.
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Adult , Humans , Male , Biomechanical Phenomena , Finite Element Analysis , Foot , Diagnostic Imaging , Imaging, Three-Dimensional , Models, Anatomic , Tomography, Spiral ComputedABSTRACT
@#Objective To evaluate the stability of the pelvic ring reconstruction using fibular autograft for periacetabular tumor type Ⅱ resection. Methods 6 adult cadaveric specimens were tested. The periacetabular tumor resection models were established according to Ennecking's type Ⅱ resection. The resected pelvic rings were reconstructed with double-fibular graft fixed by four internal fixation techniques including plates, pedicle-rods (PR), lateral-rods (LR) or sacral-iliac rods (SIR). Axial loading from the proximal L3 vertebral body was applied by MTS load cell in the gradient of 0～500 N in the double feet standing state. Images in front view were obtained using CCD camera. Based on Image J software, displacement of the first sacral vertebrae （S1） of the reconstructed pelvis and intact pelvis were calculated using digital maker tracing method with center-of-mass algorithm. Results The rotational movements and vertical displacement of S1 around the normal side femoral head of the reconstructed pelvis in coronary plane were found in simulated bilateral leg standing position. The average vertical load-displacement and load-angular rotation curve of S1 in coronary plane were approximately linear behavior under the vertical load 500 N. The average vertical displacement and angle of S1 in coronary plane had not overacted. The stability of axial direction and rotation had not changed significantly when reconstructed by LR or Plates compared with the intact pelvis, but the SIR did. Conclusion Plates and LR fixation were more stabile for periacetabular tumor type Ⅱ resection.
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Objective To measure stress distribution of the main bone architecture of the normal adult cadaveric foot and discuss the effect of plantar ligament injury on stress distribution. Methods Seven fresh adult cadaveric feet were used and 10 strain gauges attached to the bones of the longitudinal foot arch,including the calcaneus,navicular,medial cuneiform,1-5 metatarsal trunk,the distal part of the tibia and fibular,respectively.After the loading Was added to 700 N by almighty test machine,resistance strainmeter was used to measure surface strain of these bones.The results were processed statistically. Results The strain was varied based on different bone segments attached and increased with loading.Tensile force was always found at the medial part of the navicular,the distal part of the tibia and fibular,while the others showed compression all the time.Peak strain was found at calcaneus.followed by the second and third metatarsal.Strain on the surface of the bone segments changed greatly with different ligament injury(P＜0.05).Conclusion The bone surface stress of the longitudinal foot arch changes significantly when the plantar ligament is injured.
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@#Objective To investigate the morphological effect of fluid shear stress on pig iliac endothelium cells cultured solely or co-cultured with pig small intestinal submucosa.Methods The shear stress of 40×10-5 N/cm2 were carried out for 12 h on both groups.The images were recorded every 30 min.The directional angles were calculated.Results In the group of cell cultured solely:The defluvium of cells was obvious at the 1st hour,but the shape of cells didn't change.At the 4th hour,the defluvium of cells was little,the cell became round from its initiatory polygon shape.At the 8th hour,the defluvium of cell could not be observed.The shape of cells became fusiform and gracile.The cells arranged along the direction of flow field in the local area.At the 12th hour,the cells became more and more gracile.The trend of realignment of cells along the direction of flow field was obviously.The directional angles of cells at the 12th hour was significantly different from the zero hour.In the group of cell co-cultured with small intestinal submucosa:At the 1st hour,some of cells were brushed off mildly.The defluvium of cells could not been observed since the 2nd hour.The directional angles didn't change significantly in the 12 hours.Conclusion The shear stress of 40×10-55 N/cm2 cannot influence the cell of co-cultured but do influence the cell cultured solely.
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BACKGROUND: The biomechanical features of Swan-like memory compression connector designed for fractures in hemerus or the parts adjacent to joints are analyzed through biomechanical calculation and experimental measurements.OBJECTIVE: To analyze the relative memory biomechanieal significance through biomechanical measurement of Swan-like memory compression connectorDESIGN: Both biomechanieal calculation and the experimental measurement were conducted for mutual supplementation and confirmation SETTING: The Orthopaedic Department of Changhai Hospital Affiliated to Second Military Medical University of Chinese PLA and the Life Science and Tissue Engineering Institute of Tongji University MATERIALS: This experiment was conducted at the laboratory of Orthopaedic Department of Changhai Hospital Affiliated to Second Military Medical University of Chinese PLA and the Life Science and Tissue Engineering Institute of Tongji University between January 2001 and May 2003.Totally 20 hemerus from adult males who died of craniocerebral injury were chosen.METHODS: Humid hemerus from the adult corpse was chosen to prepare fracture. Encircling the prescale followed by fixation of Swan-like memory compression connector, then we measured the stress produced by compression part and encircle part at fixing the fracture.MAIN OUTCOME MEASURES: ①The stress of holding part; ② the stress of the compression part RESULTS: The stress range of holding part contacting with humerus was 2.42-22.68 N, and the stress in the fracture face, which was produced by compression part, was about 13.6 Mpa.CONCLUSION: The stress of holding part of Swan-like memory compression connector is useful in fixing the fracture parts of humerus, and the stress of compression part is suitable for the healing of fracture.
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BACKGROUND: The biomechanical features of arch-dental shape memory connector designed for fractures in pelvis or the parts adjacent to joints are analyzed through biomechanical calculation and experimental measurements.OBJECTIVE: To explore the relationship between the changes in shape of arch-dental shape memory connector and the load on it.DESIGN: Both biomechanical calculation and the experimental measurement were conducted for mutual supplementation and confirmation.SETTING: The Orthopedic Department of Changhai Hospital Affiliated to the Second Military Medical University of Chinese PLA and the Life Science and Bioengineering College of Tongji University.MATERIALS:The trial was conducted from at Shanghai Changhai Hospital and Life Science Laboratory of Tongji University from April 2002 to April 2004. The subjects were arch-dental shape memory connectors.METHODS: We calculated the stress in and around the fracture face produced by arch-dental shape memory connector according to Moire principle and we also measured the changes in the shape of arch-dental shape memory connector. The relationship between load and the changes in the shape of arch-dental shape memory connector was explored.MAIN OUTCOME MEASURES: To explore whether the results of biomechanical calculation and those of the experimental measurement are consistent.RESULTS: Biomechanical calculation found that the relationship between the load (P) and the displacement(δ) in arch-dental shape memory connector was P = 13.69δ. The experimental measurement found that the load on the connector and the displacement were in a linear relationship.CONCLUSION: The relationship between the load and the displacement in arch-dental shape memory connector was linear within its elastic range and the biomechanical calculation results were consistent with the results of the experimental measurement.
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BACKGROUND: During the therapy of the fracture of humerus, the main problem is the loading direction and power of the stress.OBJECTIVE: To analyze the choice of the different loading manners using Swain Memory Compression Bone Reduction Apparatus so as to provide the clinical evidence for the set position of the internal fixation apparatus, the loading direction and power during the therapy of the fracture of humerus.DESIGN: To construct the three-dimensional finite element model of the fracture of humerus with different loading manners.SETTING: Department of Orthopaedics of Changhai Hospital of Second Military Medical University of Chinese PLA; College of Life Sciences and Bioengineering of Tongji University,MATERIALS: The study was conducted during the period from January 2001 to May 2003 in the Orthopedic Laboratory of Changhai Hospital of Second Military Medical University of Chinese PLA and the laboratory of Life Science and Bioengineering Academy of Tongji University. The samples of the humerus taken from the wet adult cadavers, and the Swain Memory Compression Bone Reduction Apparatuses of the corresponding size were prepared.METHODS: The CT scanning was done on the samples of the wet humerus to obtain the cross section image of each layer of the humerus.The images were analyzed by a large-scale finite element analysis software ANSYSS.6 to construct the three-dimensional model of the humerus, Swain Memory Bone Reduction Apparatus and the fixed humerus using Swain Memory Bone Reduction Apparatus.MAIN OUTCOME MEASURES: To get the reference values for the clinical therapy through the comparison of the power endurance with different loading manners.RESULTS: The three-dimensional model of the fixed humerus using Swain Memory Bone Reduction Apparatus reflects the real anatomical configuration and the biomechanics behavior; meanwhile the status of the power endurance of humerus with different loading manners is also obtained.CONCLUSION: The three-dimensional model of the fixed humerus using Swain Memory Bone Reduction Apparatus may provide an accurate model for the basic study of the biomechanics behavior of the normal and fixed humerus after the fracture.
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BACKGROUND: Various therapies can be used to treat humeral fracture,but serious complications like bone disunion, etc. Are often left over. New biomechanical analytical methods are tried to be applied to provide new approaches for the functional prognosis in humeral fracture and bone disunion.OBJECTIVE: To construct humeral three-dimension model to explore its correlated biomechanical significance.DESIGN: To construct humeral three-dimension finite element model. SETTING: Department of orthopedics of a military medical university-affiliated hospital and institute for biological science and bioengineering of a university.PARTICIPANTS: The study was conducted in Shanghai Changhai Hospital and the Laboratory of Biological Science of Shanghai Tongji University. One piece of typical adult wet humerus sample was selected.INTERVENTIONS: Cross section image of each humeral layer was obtained from the selected wet humerus sample by CT scanning, and humeral three-dimensional model was constructed by large finite element analytic software ANSYS5.6.MAIN OUTCOME MEASURES: ① Biomechanical features of the constructed humeral three-dimension mode; ② Differences from clinical reality and key similarities.RESULTS: The constructed humeral three-dimensional model vividly reflected the true humeral anatomic morphology and biomechanical behavior. Its precision was judged by the comparison with CT image.CONCLUSION: The construction of humeral three-dimension finite element model provides a precise model for the researches of normal humeral mechanical behavior and the basic mechanics of internal fixation after fracture.
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BACKGROUND: The most frequently encountered problem that an orthopedic doctor encounters in treating humerus fracture is how to choose the exact direction and amount of load applied on humerus.OBJECTIVE: To explore the clinical significance of establishing a three-dimensional model and finite element analysis in treating humerus fracture and to provide theoretical basis for applying appropriate axial stress.DESIGN: The three dimensional model of humerus was reconstructed, on which compression from different directions was applied.SETTING: Orthopedic department of an affiliated hospital and life science laboratory of a university.MATERIALS: A humerus specimen received CT scanning and the trial was conducted in Shanghai Changhai Hospital and Life Science Laboratory of Tongji University from April 2002 to April 2004.METHODS: The three dimensional model of humerus was established and relevant calculation was completed with ANSYS 5.6 software. The humerus model was divided into 2 729 nodes and 49 041 units based on a three-dimensional ten-node tetrahedron as one unit. The distribution and intensity of axial compression on the fracture gap section were calculated and analyzed in the following conditions, i. e. when the humerus was fixed in X, Y and Z directions and the fracture gap section was 30°, 45°, 90° to Z axis.MAIN OUTCOME MEASURES: The axial pressure on the fracture gap section in different conditions to provide evidence for clinical treatment.RESULTS: The stress applied on the fracture gap was relatively concentrated and was 2 -3 times stronger than that in other areas, and it was generally symmetrically distributed within 10 mm around the fracture gap.CONCLUSION: The required load on humerus fracture should be calculated before a suitable implant is applied to accommodate the movement of humerus without compromising healing of the fracture.
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Objective To analyze the mechanical mechanism of suburethral slings by measuring the mechanical properties of female pig urethra wall and polypropylene mesh.Methods The uniaxial tension tests of 49 female pig urethra wall strips and 27 polypropylene mesh samples were performed to test the mechanical properties.Results The stress and strain of urethra wall displayed a parabola shape and its elastic modulus was proportional to the square root of stress as well as the strain.The maximum calculated elastic moduli of the urethra wall were 0.806 MPa and 0.818 MPa correspondingly calculated with stress and strain.The elastic modulus of polypropylene mesh was(6.977?1.095) MPa.The ultimate stress of polypropylene mesh was significantly higher than that of the urethra wall,and the ultimate strain of polypropylene mesh was significantly lesser than that of the urethra wall.The calculation results suggested that the suburethral slings treatment of poly-propylene mesh decreased the deformation to 1/3 of the untreated stress urinary incontinence.Conclusion Polypropylene mesh has special mechanical properties that suit suburethral slings and enhance the support to the urethra,and improve the continence.
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Objective:To study the biomechanical basis of swan like memory compressive connector (SMC) for treating fractures and nonunions, and the facilitating effects of dynamic memorial stress of SMC for bone healing. Methods:By computer emulation and three dimensional (3D) finite element analysis, the biomechanical behavior of humeral type connector for fixing humerus was emulated and analyzed. The finite element model of humeral type connector was divided into 3 487 units. The number of nodes was 5 397. The element was a unit with 20 nodes, 4 faces. The finite element model of humerus was divided into 5 783 units, the number of nodes was 9 863. And the finite element was a 3D unit with 10 nodes, 4 faces.Results:When the connector fixated humerus, it came in for tension stress in its inner surface, and compressing stress in its outer surface. The maximum first structural major stress of metamorphosed compressive part was 224.5 MPa and -34 MPa, far less than its utmost stress and fatigue limit. The initiative memorial bone holding force for maintaining axial stability was 125.05 N, and the longitudinal initiative memorial compression force was 196 N. The stress distribution in fixed humerus was even, the stress in most nodes was positive stress. Conclusion:The SMC has good anti fatigue and reuse characters. The dynamic memorial compressive stress field is good for the stability of fixation and enhancement of bone healing.