• Volume 25,Issue 3,2010 Table of Contents
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    • Advances on biomechanical model of human upper airway

      2010, 25(3):157-162. DOI: 10.3871/j.1004-7220.2010.3.162.

      Abstract (2598) HTML (0) PDF 826.71 K (3274) Comment (0) Favorites

      Abstract:Rebuilding the biomechanical model of human upper airway is an effective method for studying upper airway structure of human and its function, and it is also helpful to predict and make the treatment for upper airway diseases. This paper summarized the advances on biomechanical model of human upper airway and its application in clinical treatment, as well as try to make prediction about the research work in the future.

    • Effect of tympanic membrane perforation on vibration of hearing system

      2010, 25(3):163-168. DOI: 10.3871/j.1004-7220.2010.03.168.

      Abstract (2461) HTML (0) PDF 676.65 K (2978) Comment (0) Favorites

      Abstract:Objective To study the effects of the size and diffraction of tympanic membrane perforation on hearing system of human ear. Method The whole temporal bone from a healthy volunteer is scanned using spiral CT. The digitized outlines of images are imported into ANSYS to construct a three dimensional finite element model of the human ear. ResultsThe resonance frequencies become 3.6, 4.4 and 4.6 kHz with the increase of perforation areas as 0.97, 3.66 and 7.97 mm2, respectively. The larger perforation in the tympanic membrane results in a lower stapes footplate displacement. The displacement swing of the stapes footplate decreased clearly under the action of sound wave from the diffraction. The peak values of the displacement nephogram of the tympanic membrane are 0.32, 0.20 and 0.19 μm at 1000 Hz, respectively. At the resonance frequency, the peak values of the displacement nephogram of the tympanic membrane are 0.20, 0.14 and 0.09 μm, respectively. Conclusions The larger the size of the perforation is, the smaller stapes footplate displacement will be, especially at the lower frequency of 4 kHz with the higher resonance frequency. The peak values of displacement nephogram will become smaller with the increased size of perforations. The results would give helpful information for the clinical treatment.

    • Numerically simulating the biomechanical response to membranous labyrinth in the vestibular system

      2010, 25(3):169-174. DOI: 10.3871/j.1004-7220.2010.3.174.

      Abstract (2437) HTML (0) PDF 755.25 K (3332) Comment (0) Favorites

      Abstract:Objective To study the biomechanical response to cupulae partition of statoreceptor in the rotational chair test and to provide a quantitive platform for vestibular system assessment. Method Based on the histological slides from the right temporal bones from a healthy volunteer, a threedimensional geometry of membranous labyrinth in the vestibular system was reconstructed. The biomechanical response of the volunteer to sinusoidal rotation chair test (0.8 Hz, ±40°) with the head pitch 30° was numerically simulated by the Lagrangian method. ResultsThe maximum displacement of cupula partition in the right horizontal semicircular canal is 54.2 μm, and 15.9 μm in the posterior semicircular canal as well as 43.7 μm in the anterior semicircular canal. However, the displacement response in the anterior semicircular canal is identical on both ears, and it would counteract the eye movement. Secondly, the normal displacement in the right semicircular canal deflect from the side of canal to the side of utricle, while in the left semicircular canal, it deflect from the side of utricle to the side of canal when the chair rotated to the right, and it is opposite when the chair rotate to the left. Conclusions The biomechanical response to cupulae partition by this numerical simulation is in accordance with Flourens law and Ewald laws.

    • Effect of different connecting methods for artificial ossicle on dynamic response of ear

      2010, 25(3):175-181. DOI: 10.3871/j.1004-7220.2010.3.181.

      Abstract (1930) HTML (0) PDF 729.36 K (2621) Comment (0) Favorites

      Abstract:Objective To study the effects of the different connecting mode of artificial ossicle on hearing restoration. Method Geometrical model of human ear was established by an original C++ program based on clinical CT data, and imported this geometrical model into finite element software PATRAN to build up the numerical finite element model of human ear structure. Based on the finite element model, the fluidsolid coupling was computed by harmonic response analysis method, and the effect of sound conduction on ear structure was analyzed according to different implantable methods and positions of artificial ossicle. Results The validity of this numerical model is confirmed by comparing the amplitude of umbo and stapes footplate on numerical model which is gained by dynamic response analysis on normal ear structure with published experimental measurements on human temporal bones. ConclusionsConnecting artificial ossicle to tympanic membrane at its central position is optimal for the dynamic response of ear structure as the amplitude of stapes footplate under this situation is slightly higher than other connecting methods since it conforms to physiological function of human ear, and the effect of hearing recovery could be better.

    • Effect of different connecting methods for artificial ossicle on dynamic response of ear

      2010, 25(3):175-181. DOI: 10.3871/j.1004-7220.2010.03.181.

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      Abstract:Objective To study the effects of the different connecting mode of artificial ossicle on hearing restoration. Method Geometrical model of human ear was established by an original C++ program based on clinical CT data, and imported this geometrical model into finite element software PATRAN to build up the numerical finite element model of human ear structure. Based on the finite element model, the fluidsolid coupling was computed by harmonic response analysis method, and the effect of sound conduction on ear structure was analyzed according to different implantable methods and positions of artificial ossicle. Results The validity of this numerical model is confirmed by comparing the amplitude of umbo and stapes footplate on numerical model which is gained by dynamic response analysis on normal ear structure with published experimental measurements on human temporal bones. ConclusionsConnecting artificial ossicle to tympanic membrane at its central position is optimal for the dynamic response of ear structure as the amplitude of stapes footplate under this situation is slightly higher than other connecting methods since it conforms to physiological function of human ear, and the effect of hearing recovery could be better.

    • Measuring iris elastic modulus based on holistic iris deformation experiment

      2010, 25(3):182-185. DOI: 10.3871/j.1004-7220.2010.03.185.

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      Abstract:Objective To measure the iris elastic modulus. Method Using the selfdesigned device, the information of in vitro holistic iris deformation of rabbits were obtained with the loadpressure increasing gradually from 0 Pa to 600 Pa, and the heights of such iris were computed. The corresponding model based on experimental data was established and analyzed by ANSYS finite element software, and the iris elastic modulus was computed by a reverse method. Results The elastic modulus is 6.1 kPa at 100 Pa load pressure. ConclusionsThe iris material can be considered as linear elastic model when the pressure difference between the anterior chamber and posterior chamber is low.

    • Measuring iris elastic modulus based on holistic iris deformation experiment

      2010, 25(3):182-185. DOI: 10.3871/j.1004-7220.2010.3.185.

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      Abstract:Objective To measure the iris elastic modulus. Method Using the selfdesigned device, the information of in vitro holistic iris deformation of rabbits were obtained with the loadpressure increasing gradually from 0 Pa to 600 Pa, and the heights of such iris were computed. The corresponding model based on experimental data was established and analyzed by ANSYS finite element software, and the iris elastic modulus was computed by a reverse method. Results The elastic modulus is 6.1 kPa at 100 Pa load pressure. ConclusionsThe iris material can be considered as linear elastic model when the pressure difference between the anterior chamber and posterior chamber is low.

    • Effects of mechanical stimulation on proliferation activity and CTGF expression of sclera fibroblasts

      2010, 25(3):186-189. DOI: 10.3871/j.1004-7220.2010.3.189.

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      Abstract:Objective To study the effects of mechanical stimulation on proliferation activity and connective tissue growth factor(CTGF) expression of sclera fibroblasts. Method The sclera fibroblasts from New Zealand white rabbits were obtained by tissue pieces culture method and identified with immunocytochemistry method, as well as tested by FX4000 Tension System (sine wave, 3% and 6% elongation amplitude, 0.1Hz, 48h duration). The proliferation activity and concentration of CTGF were measured by ATP based bioluminescence method and ELISA method, respectively. ResultsExperimental studies have shown that the proliferation activity of the scleral fibroblasts in 3% group (2.352±0.123) and 6% group (2.784±0.119) are significantly higher when compared with control group (1.901±0.092) (P<0.05), and the proliferation activity in 6% group is significant higher than that in 3% group (P<0.05); The CTGF expression of 3% group (control group: (0.291±0.118)μg/L, 3% stretch group: (1.623±0.276)μg/L) and 6% group (control group: (0.260±0.112)μg/L, 6% stretch group: (3.205±0.287)μg/L) are both significantly increased compared with each of their respective control groups (P<0.05). Conclusions Mechanical stimulation plays an important role in the proliferation activity and CTGF expression of scleral fibroblasts.

    • Effects of mechanical stimulation on proliferation activity and CTGF expression of sclera fibroblasts

      2010, 25(3):186-189. DOI: 10.3871/j.1004-7220.2010.3.189.

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      Abstract:Objective To study the effects of mechanical stimulation on proliferation activity and connective tissue growth factor(CTGF) expression of sclera fibroblasts. Method The sclera fibroblasts from New Zealand white rabbits were obtained by tissue pieces culture method and identified with immunocytochemistry method, as well as tested by FX4000 Tension System (sine wave, 3% and 6% elongation amplitude, 0.1Hz, 48h duration). The proliferation activity and concentration of CTGF were measured by ATP based bioluminescence method and ELISA method, respectively. ResultsExperimental studies have shown that the proliferation activity of the scleral fibroblasts in 3% group (2.352±0.123) and 6% group (2.784±0.119) are significantly higher when compared with control group (1.901±0.092) (P<0.05), and the proliferation activity in 6% group is significant higher than that in 3% group (P<0.05); The CTGF expression of 3% group (control group: (0.291±0.118)μg/L, 3% stretch group: (1.623±0.276)μg/L) and 6% group (control group: (0.260±0.112)μg/L, 6% stretch group: (3.205±0.287)μg/L) are both significantly increased compared with each of their respective control groups (P<0.05). Conclusions Mechanical stimulation plays an important role in the proliferation activity and CTGF expression of scleral fibroblasts.

    • Biomechanical properties of fibroblasts after posterior scleral reinforcement treatment for rabbit experimental myopia

      2010, 25(3):190-194. DOI: 10.3871/j.1004-7220.2010.03.194.

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      Abstract:Objective To evaluate the biomechanical properties of fibroblasts for rabbit experimental myopia after Posterior Scleral Reinforcement (PSR) treatment, and discuss the mechanism of PSR in myopia treatment as viewed from biomechanics. Method 45 rabbits of threeweekold were randomly monocular treated by eyelid suture to prepare experimental myopia eye. After 60 days, the experimental myopia eyes were divided into two groups randomly. Group A was treated by PSR. Group B was treated by similar operation without placing reinforce strap. After three months and six month, the fibroblasts from each group were isolated and cultured in vitro respectively. The cultured cells were then determined to be fibroblasts by using immunocyte chemistry method. Micropipette aspiration technique was used to investigate the viscoelastic properties of the fibroblasts from each group with mechanical model of semiinfinite somatic cells. ResultsThree months after operation, the viscoelastic properties of the scleral fibroblasts in Group A and Group B exhibit no significant difference (P>0.05) three months and six months as well (P>0.05) after operation with the equilibrium modulus, E∞, and apparent viscosity, μ of the scleral fibroblasts in Group A (E = (361.2± 121.1)Pa、μ=(2928.2±669.4)Pa·s) compared with that in Group B (E =(347.6± 82.1)Pa、μ=(2820.6± 593.5)Pa·s). Neither in Group A nor Group B, the E∞ and μ at different stages after operation have significant difference (P>0.05). The E∞ and μ in transition zone tissues at different stages after operation have no significant difference(P>0.05) either. Conclusions The enhancement of PSR is caused by transition zone tissues and the strip itself.

    • Biomechanical properties of fibroblasts after posterior scleral reinforcement treatment for rabbit experimental myopia

      2010, 25(3):190-194. DOI: 10.3871/j.1004-7220.2010.3.194.

      Abstract (1980) HTML (0) PDF 630.75 K (2722) Comment (0) Favorites

      Abstract:Objective To evaluate the biomechanical properties of fibroblasts for rabbit experimental myopia after Posterior Scleral Reinforcement (PSR) treatment, and discuss the mechanism of PSR in myopia treatment as viewed from biomechanics. Method 45 rabbits of threeweekold were randomly monocular treated by eyelid suture to prepare experimental myopia eye. After 60 days, the experimental myopia eyes were divided into two groups randomly. Group A was treated by PSR. Group B was treated by similar operation without placing reinforce strap. After three months and six month, the fibroblasts from each group were isolated and cultured in vitro respectively. The cultured cells were then determined to be fibroblasts by using immunocyte chemistry method. Micropipette aspiration technique was used to investigate the viscoelastic properties of the fibroblasts from each group with mechanical model of semiinfinite somatic cells. ResultsThree months after operation, the viscoelastic properties of the scleral fibroblasts in Group A and Group B exhibit no significant difference (P>0.05) three months and six months as well (P>0.05) after operation with the equilibrium modulus, E∞, and apparent viscosity, μ of the scleral fibroblasts in Group A (E = (361.2± 121.1)Pa、μ=(2928.2±669.4)Pa·s) compared with that in Group B (E =(347.6± 82.1)Pa、μ=(2820.6± 593.5)Pa·s). Neither in Group A nor Group B, the E∞ and μ at different stages after operation have significant difference (P>0.05). The E∞ and μ in transition zone tissues at different stages after operation have no significant difference(P>0.05) either. Conclusions The enhancement of PSR is caused by transition zone tissues and the strip itself.

    • Effect of ocular hypertension on the function of retina of glaucoma

      2010, 25(3):195-199. DOI: 10.3871/j.1004-7220.2010.3.199.

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      Abstract:Objective To explore the effect of elevated intraocular pressure (IOP) on retina's function of rat. Method Chronic glaucoma rat models were built and IOP were measured persistently. Flash electroretinogram (FERG) and histological status were measured before and after surgery. ResultsThe maximal IOP in rats without anesthesia is (3.07±1.10) kPa in 1 day after surgery. From 1 w to 6 w after surgery, the modeleyeIOPs are (2.84±0.90) kPa,(2.86±0.54) kPa,(2.76±0.52) kPa,(2.70±0.51) kPa,(2.39±0.27) kPa and(2.09±0.39) kPa, respectively, which are significant higher than that of the fellow eye. A series of main parameters including the amplitudes of awave, bwave and oscillatory potentials(OPs) all dramatically decreased in model eyes at 6 weeks and 3 weeks postoperatively . No obvious changes were observed by routine HE staining among the eyes before and after surgery. Conclusions The chronic high intraocular pressure could induce the retinal dysfunction before any morphological change occurred, and what's more, the damage showed itself a progressive one.

    • Effect of ocular hypertension on the function of retina of glaucoma

      2010, 25(3):195-199. DOI: 10.3871/j.1004-7220.2010.03.199.

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      Abstract:Objective To explore the effect of elevated intraocular pressure (IOP) on retina's function of rat. Method Chronic glaucoma rat models were built and IOP were measured persistently. Flash electroretinogram (FERG) and histological status were measured before and after surgery. ResultsThe maximal IOP in rats without anesthesia is (3.07±1.10) kPa in 1 day after surgery. From 1 w to 6 w after surgery, the modeleyeIOPs are (2.84±0.90) kPa,(2.86±0.54) kPa,(2.76±0.52) kPa,(2.70±0.51) kPa,(2.39±0.27) kPa and(2.09±0.39) kPa, respectively, which are significant higher than that of the fellow eye. A series of main parameters including the amplitudes of awave, bwave and oscillatory potentials(OPs) all dramatically decreased in model eyes at 6 weeks and 3 weeks postoperatively . No obvious changes were observed by routine HE staining among the eyes before and after surgery. Conclusions The chronic high intraocular pressure could induce the retinal dysfunction before any morphological change occurred, and what's more, the damage showed itself a progressive one.

    • Establishing finite element contact model of human L1~L5 lumbar segments

      2010, 25(3):200-205. DOI: 10.3871/j.1004-7220.2010.3.205.

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      Abstract:Objective To establish the finite element model of L1~L5 lumbar motion segments with contact theory by self-compiled software and HyperMesh. Method Based on the spine CT continuous images of L1~L5 segments from the healthy volunteer, the three dimensional finite elements model of L1~L5 vertebrae structure was constructed applying self compiled software and HyperMesh, and added with simulating the endplates, joint cartilage intervertebral disc as well as ligament structure. The contact theory was adopted to solve the process between the high and low articular surface surface contacting. ResultsThe three dimensional finite element model with more structure integrity and good geometric similarity was obtained. The simulating results of the physical loading are matched better with the results of the vitro experiment of biomechanics. Conclusions Selfcompiled software and HyperMesh improved the speed and accuracy for building finite element model of lumbar motion segment, while the introduction of contact theory could enhance its reliability and authenticity.

    • Establishing finite element contact model of human L1~L5 lumbar segments

      2010, 25(3):200-205. DOI: 10.3871/j.1004-7220.2010.3.205.

      Abstract (2042) HTML (0) PDF 719.08 K (2734) Comment (0) Favorites

      Abstract:Objective To establish the finite element model of L1~L5 lumbar motion segments with contact theory by self-compiled software and HyperMesh. Method Based on the spine CT continuous images of L1~L5 segments from the healthy volunteer, the three dimensional finite elements model of L1~L5 vertebrae structure was constructed applying self compiled software and HyperMesh, and added with simulating the endplates, joint cartilage intervertebral disc as well as ligament structure. The contact theory was adopted to solve the process between the high and low articular surface surface contacting. ResultsThe three dimensional finite element model with more structure integrity and good geometric similarity was obtained. The simulating results of the physical loading are matched better with the results of the vitro experiment of biomechanics. Conclusions Selfcompiled software and HyperMesh improved the speed and accuracy for building finite element model of lumbar motion segment, while the introduction of contact theory could enhance its reliability and authenticity.

    • Three dimensional finite element analysis of stress distribution on continuously varying of length of pedicle screw

      2010, 25(3):206-211. DOI: 10.3871/j.1004-7220.2010.3.211.

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      Abstract:Objective To study the stress distribution on different length of pedicle screws under the physiological load by using the three dimensional finite element analysis. Method A threedimension model of the pedicle screw and L1 vertebral body were constructed with the model meshed on the basis of the finite element method. The feature dimension of pedicle screw in the model was set in a specified varied range. Under the physiological load, the stress on every model with different diameter sizes of pedicle screw was analyzed. ResultsThe stress on every bone model decreased with the increase of stress on screw under the axially pullout force as the length of screw ranged from 30mm to 50mm. And the maximum Equivalent Stress (EQV Stress) in the pedicle screw appeared in the central area of the pedicle screw, the maximum Equivalent Stress (EQV Stress) in the cortical bone appeared in both sides of contact surface, the maximum Equivalent Stress (EQV Stress) of the cancellous bone appeared in both sides of contact surface of the top of pedicle screw and cancellous bone. In a certain external load, with the 50mm length of screw, the load that transfers to the cortical bone and cancellous bone is reduced by 43.1% and 42.3%, respectively, while the maximum Equivalent Stress (EQV Stress) of screw was increased 38%. When L≥45mm, the variable stress on all models become stable. Conclusions While the length of screw is in range of 4.0 mm to 6.5 mm, 30~50 mm ,the increase of pedicle screw length could improve the distribution of axial pullout stress on the screws, cortical bone and cancellous bone. As long as the bone mass allowed, the length of pedicle screws should be not less than 45mm in clinical choice.

    • Three dimensional finite element analysis of stress distribution on continuously varying of length of pedicle screw

      2010, 25(3):206-211. DOI: 10.3871/j.1004-7220.2010.03.211.

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      Abstract:Objective To study the stress distribution on different length of pedicle screws under the physiological load by using the three dimensional finite element analysis. Method A threedimension model of the pedicle screw and L1 vertebral body were constructed with the model meshed on the basis of the finite element method. The feature dimension of pedicle screw in the model was set in a specified varied range. Under the physiological load, the stress on every model with different diameter sizes of pedicle screw was analyzed. ResultsThe stress on every bone model decreased with the increase of stress on screw under the axially pullout force as the length of screw ranged from 30mm to 50mm. And the maximum Equivalent Stress (EQV Stress) in the pedicle screw appeared in the central area of the pedicle screw, the maximum Equivalent Stress (EQV Stress) in the cortical bone appeared in both sides of contact surface, the maximum Equivalent Stress (EQV Stress) of the cancellous bone appeared in both sides of contact surface of the top of pedicle screw and cancellous bone. In a certain external load, with the 50mm length of screw, the load that transfers to the cortical bone and cancellous bone is reduced by 43.1% and 42.3%, respectively, while the maximum Equivalent Stress (EQV Stress) of screw was increased 38%. When L≥45mm, the variable stress on all models become stable. Conclusions While the length of screw is in range of 4.0 mm to 6.5 mm, 30~50 mm ,the increase of pedicle screw length could improve the distribution of axial pullout stress on the screws, cortical bone and cancellous bone. As long as the bone mass allowed, the length of pedicle screws should be not less than 45mm in clinical choice.

    • Biomechanical test and clinical application of EZ extraction screws device

      2010, 25(3):212-216. DOI: 10.3871/j.1004-7220.2010.03.216.

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      Abstract:Objective To evaluate the effect of EZ extraction screws device on screwing out the reduced screws,broken screws, skidded screws in biomechanical test and clinical application. Method 4 femurs, tibias, radius, ulnas of 4 fresh skeleton specimen were divided into two big groups randomly as Group A and Group B1, B2 and B3: In Group A the screws were taken out by screwdriver; In Group B, the screws were clamped in medulla cavity filled with the bone cement,;B1 was the group of measuring skidded screws with the biggest torsion; B2 was the group of measuring skidded screws with the biggest torsion by one handle; B3 was by two handles. Four mechanics test models were made, and the clamping screws were divided into two types of 4.5 mm and 3.5 mm each for 60. The experiment specimen were tested on the universal testing machines with exerting 2 kN axial loading, and surveyed the greatest torque, the torsion angle and the power loss as well as the efficiency when drawing out. The empirical datum after statistics processing were compared among the groups. And EZ was also used for 12 example patients in the preliminary clinical practice. ResultsGroup A showed the biggest torque as 1.42~1.96 N·m for drawing out; Group B1 as 2.87~3.27 N·m; Group B2 as 3.06~4.83 N·m; Group B3 as 4.12~8.36 N·m. The significant difference (P<0.05)was found in each group. The average value of torsion angle in each corresponding group is 1.59°,0.77°,0.28° and 0.16°, respectively with the obvious difference (P<0.05); The average value of power loss in each group is 12, 21, 32 and 45J respectively; and the power (mechanical efficiency) in each corresponding group is 0.20, 0.35, 0.53 and 0.75 T/s, respectively, which also showed the obvious difference (P<0.05). EZ used in 12 cases were successfully screwed out with all the broken screws and maintained the integrity of the bone without any postoperative complications. Conclusions EZ extraction screw device has sufficient torsional strength and stiffness with enough clamping force, and could pull out stably and reliably, which is an ideal tool for the stub screws, crooked screws and slipped screws in skeleton.

    • Biomechanical test and clinical application of EZ extraction screws device

      2010, 25(3):212-216. DOI: 10.3871/j.1004-7220.2010.3.216.

      Abstract (1753) HTML (0) PDF 605.39 K (2622) Comment (0) Favorites

      Abstract:Objective To evaluate the effect of EZ extraction screws device on screwing out the reduced screws,broken screws, skidded screws in biomechanical test and clinical application. Method 4 femurs, tibias, radius, ulnas of 4 fresh skeleton specimen were divided into two big groups randomly as Group A and Group B1, B2 and B3: In Group A the screws were taken out by screwdriver; In Group B, the screws were clamped in medulla cavity filled with the bone cement,;B1 was the group of measuring skidded screws with the biggest torsion; B2 was the group of measuring skidded screws with the biggest torsion by one handle; B3 was by two handles. Four mechanics test models were made, and the clamping screws were divided into two types of 4.5 mm and 3.5 mm each for 60. The experiment specimen were tested on the universal testing machines with exerting 2 kN axial loading, and surveyed the greatest torque, the torsion angle and the power loss as well as the efficiency when drawing out. The empirical datum after statistics processing were compared among the groups. And EZ was also used for 12 example patients in the preliminary clinical practice. ResultsGroup A showed the biggest torque as 1.42~1.96 N·m for drawing out; Group B1 as 2.87~3.27 N·m; Group B2 as 3.06~4.83 N·m; Group B3 as 4.12~8.36 N·m. The significant difference (P<0.05)was found in each group. The average value of torsion angle in each corresponding group is 1.59°,0.77°,0.28° and 0.16°, respectively with the obvious difference (P<0.05); The average value of power loss in each group is 12, 21, 32 and 45J respectively; and the power (mechanical efficiency) in each corresponding group is 0.20, 0.35, 0.53 and 0.75 T/s, respectively, which also showed the obvious difference (P<0.05). EZ used in 12 cases were successfully screwed out with all the broken screws and maintained the integrity of the bone without any postoperative complications. Conclusions EZ extraction screw device has sufficient torsional strength and stiffness with enough clamping force, and could pull out stably and reliably, which is an ideal tool for the stub screws, crooked screws and slipped screws in skeleton.

    • Anatomical and Biomechanical Study of Sacral Pedicle and Lateral Mass

      2010, 25(3):217-223. DOI: 10.3871/j.1004-7220.2010.3.223.

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      Abstract:Objective To study the anatomical and biomechanical features of sacral pedicle and lateral mass to provide evidence for clinical sacral pedicle and lateral mass screw fixation technology. Method 60 adult patient's spiral CT images of sacrum and coccyx were selected randomly. The sacral pedicle and lateral mass screw entry point was determined, and the crew trajectory were measured using the three dimensional reconstruction. Meanwhile, the gross anatomy was done for 15 adult cadavers to determine the sacral pedicle and lateral mass screw entry point. The length, width and angle of sacral pedicle and lateral mass screw trajectory was measured. 8 of 15 cadaver specimens were selected to test for the maximal extraction force for sacral pedicle and lateral mass screws. ResultsThe diameter and length of S1~S5 sacral pedicle and lateral mass screw trajectory are significantly regular, with inclination angle is about 20°. The S1 pedicle screw entry point is located at intersection point of basal lateral part of articular process and median line of transverse process, no significant difference is found between the maximal extraction force of pedicle and lateral mass screws (P>0.05). The entry points of S2~5 pedicle screws are located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of transverse process. The lateral mass screw entry point of S2~5 is on the median side of intersection point between median line of transverse process and lateral sacral crest. The maximal extraction force of pedicle screws are significantly different from the lateral mass screws(P<0.05). Conclusions Both the sacral pedicle and the lateral mass screw fixation technology can offer effective fixation and reconstruction for the fracture of sacrum and coccyx, but the pedicle screw fixation may be more convenient, safe and reliable than the lateral mass screw fixation technology.

    • Anatomical and Biomechanical Study of Sacral Pedicle and Lateral Mass

      2010, 25(3):217-223. DOI: 10.3871/j.1004-7220.2010.3.223.

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      Abstract:Objective To study the anatomical and biomechanical features of sacral pedicle and lateral mass to provide evidence for clinical sacral pedicle and lateral mass screw fixation technology. Method 60 adult patient's spiral CT images of sacrum and coccyx were selected randomly. The sacral pedicle and lateral mass screw entry point was determined, and the crew trajectory were measured using the three dimensional reconstruction. Meanwhile, the gross anatomy was done for 15 adult cadavers to determine the sacral pedicle and lateral mass screw entry point. The length, width and angle of sacral pedicle and lateral mass screw trajectory was measured. 8 of 15 cadaver specimens were selected to test for the maximal extraction force for sacral pedicle and lateral mass screws. ResultsThe diameter and length of S1~S5 sacral pedicle and lateral mass screw trajectory are significantly regular, with inclination angle is about 20°. The S1 pedicle screw entry point is located at intersection point of basal lateral part of articular process and median line of transverse process, no significant difference is found between the maximal extraction force of pedicle and lateral mass screws (P>0.05). The entry points of S2~5 pedicle screws are located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of transverse process. The lateral mass screw entry point of S2~5 is on the median side of intersection point between median line of transverse process and lateral sacral crest. The maximal extraction force of pedicle screws are significantly different from the lateral mass screws(P<0.05). Conclusions Both the sacral pedicle and the lateral mass screw fixation technology can offer effective fixation and reconstruction for the fracture of sacrum and coccyx, but the pedicle screw fixation may be more convenient, safe and reliable than the lateral mass screw fixation technology.

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