2013, 28(2):127-134. DOI: 10.3871/j.1004-7220.2013.2.134.
Abstract:Asthma is an important respiratory disease that endangers human health, while its complex mechanisms of pathobiology have not been fully understood. Recently, environmental factors are increasingly recognized to play important roles in the pathogenesis of asthma. In particular, the effect of PM2.5 (particulate matter with diameter smaller than 2.5 μm) on the structure and function of pulmonary airways at cell level has become a research hotspot and frontier, and led to many important findings. In this article, the main pathological features, i.e. airway inflammation and hyperresponsiveness were discussed, and recent progress and important findings in pathological effects of PM2.5 on the airway and its mechanism were reviewed, including PM2.5 transport and deposition in the airway, PM2.5 and airway inflammation and damage, PM2.5 and airway remodeling, PM2.5 and airway hyperresponsiveness, PM2.5 and airway smooth muscle cell mechanics via either indirect regulation or direct interaction. The analysis on the role of PM2.5 in airway biomechanics in relation to asthma pathobiology will provide a valuable reference for studying effects of PM2.5 on the respiratory system.
2013, 28(2):135-141. DOI: 10.3871/j.1004-7220.2013.2.141.
Abstract:Objective To examine the aerosol particle deposition in human upper respiratory tract model and explore the pathogenesis of toxic aerosol in human upper respiratory tract. Methods A human upper respiratory tract model was constructed using ABS (Acrylonitrile Butadiene Styrene) plastic, and an experimental system was established to measure the deposition efficiency of aerosol particles with different diameters (0.3 or 6.5 μm) at different breathing intensity (30 or 60 L/min) in this model. Results The deposition patterns of aerosol particles with different diameters and at different breathing intensity in human upper respiratory tract model were similar. The deposition efficiency was generally higher in pharynx，larynx and trachea while being the highest in the area of larynx. Conclusions The breathing intensity has a major impact on aerosol deposition efficiency in the model. Larger aerosol particles are more easily to deposit in the model. Inertial impaction and turbulence intensity are the main mechanisms of aerosol particle deposition.
2013, 28(2):142-147. DOI: 10.3871/j.1004-7220.2013.2.147.
Abstract:Objective To investigate the effects of muscles and boundary conditions on head impact response. Methods Three different 3D material point impact models of human head were constructed from the CT scanned images. The first model was the simple head model (SHFr) including skull, membrane and brain, in which the head was free. The second model was the simple head model with muscle (MHFr) including skull, membrane, brain and muscle of the head, in which the head was free. The third model was the MHFr model with shoulder, in which the bottom edge of the shoulder was fixed (MHSFi). The three models were under the impact of a cylindrical lead hammer projected at a speed of 6.4 m/s to simulate the dynamic response of the three models using 3D explicit material point method code. Results The peak values of acceleration of the head centroid for the SHFr, MHFr and MHSFi model were 6.018×103, 4.69×103 and 4.76×103 m/s2, respectively. Conclusions The muscle of the head can disperse distributions of the contact force, enlarge the damage area and relieve the damage of the head. In case of short-time impact, whether the boundary of the head is free or the shoulder is fixed does not affect the dynamic response of the head impact.
2013, 28(2):148-153. DOI: 10.3871/j.1004-7220.2013.2.153.
Abstract:Objective To investigate the hemodynamic effect of stents with different types of links on treating vertebral artery stenosis, and provide scientific guidelines for the design of stent structure and the clinical procedure of stent intervention. Methods Models of vertebral artery with stenosis and three kinds of stents with different types of links (named as L-stent, V-stent and S-stentaccording to the shapes) were constructed by using Pro/Engineering. The expansions of these stents in the stenotic vertebral artery were simulated using ABAQUS, and three finite element models of the stented vertebral artery were then established for fluid flow analysis, and hemodynamic simulation was performed using ANSYS-CFX. Results Compared with V-link and S-link stent, L-link stent had smaller area of low wall shear stress distributions and smaller blood stagnation area. Conclusions With better hemodynamic effect, L-stent can potentially reduce the possibility of in-stent restenosis and provide scientific references for the choice of stent, the design of stent structure and surgical planning of stent intervention.
2013, 28(2):154-159. DOI: 10.3871/j.1004-7220.2013.2.159.
Abstract:Objective To establish the three-dimensional (3D) and biomechanical model of lower limb for kinematics and dynamics analysis, and construct the control platform of lower limb for providing theoretical basis for the design of active transfemoral prosthesis and lower limb exoskeleton orthosis. Methods Motion information of the hip joint, knee joint and ankle joint was collected by VICON 3D motion capture system. The 3D model of lower limb was designed by Solidworks for kinematics analysis. Based on SimMechanics in Matlab toolbox, the biomechanical model of lower limb was built to analyze dynamics of lower limb. Based on hardware-in-the-loop simulation platform of Quanser, the control model was constructed to receive control signal from SimMechanics and realize the control of lower limb motion platform. Results The velocity, acceleration and moment of force in each joint were obtained through kinematics and dynamics simulation. The established model of lower limb was validated by simulation, and the simulation signal was used to control the lower limbs motion platform to and realize the function of level walking. Conclusions The platform can be used for the research on kinematics, dynamics and control of lower limb, which has paved way for further investigation on the control of active transfemoral prosthesis and lower limb exoskeleton orthosis.
2013, 28(2):160-163. DOI: 10.3871/j.1004-7220.2013.2.163.
Abstract:Objective To study effects of paraquat on proliferation and viscoelasticity of human embryonic lung fibroblasts (MRC-5), and to discuss mechanism of MRC-5 damage at initial stage and pulmonary fibrosis later after paraquat intoxication. Methods MRC-5 cells were treated by culture medium with different concentration of paraquat (50, 100, 200 mg/L, respectively) for 12 hours, when the paraquat culture medium was replaced by normal culture medium. At 48th hours, MRC-5 cells were collected, examined and analyzed by flow cytometry for indicating the proliferation, and micropipette aspiration technique was used to investigate viscoelasticity of the cells. Results After treated by paraquat with different concentration, proliferation index (PI) of MRC-5 cells were significantly reduced, as compared with the control group (P<0.05), and PI was reduced with the increase of paraquat concentration; viscoelastic parameters of MRC-5 cells were significantly decreased as compared with the normal cells (P<0.05); viscoelastic parameters of MRC-5 cells in 100 mg/L group and 200 mg/L group were smaller than those in 50 mg/L group (P<0.05), and there was no significant difference between 100 mg/L group and 200 mg/L group (P>0.05). Conclusions MRC-5 cells were damaged at initial stage of paraquat intoxication, with PI and viscoelastic parameters reducing. Decompensated repair after paraquat intoxication is an important reason leading to pulmonary fibrosis, which provides a new thought in clinical treatment.
2013, 28(2):164-170. DOI: 10.3871/j.1004-7220.2013.2.170.
Abstract:Objective To study the relationship between the severity of pedestrian head injury and the impact speeds, the vehicle types and the impact positions in pedestrian-vehicle accidents by computer simulation based on the real accident video. Methods A pedestrian-traffic accident with the video was reconstructed by the MADYMO multi-body dynamics software to obtain the initial and boundary conditions. Experimental impact simulations were conducted on different vehicles (car, SUV and minibus) and pedestrian impact positions (front, side and back structure) by different speeds (20, 30, 40, 50 and 60 km/h) to analyze head injuries, and the simulation results were validated by two real pedestrian-vehicle accidents. Results Not only the impact speed and the front structure influenced the pedestrian head injury severity, but also the impact position of pedestrian was an important factor. At the collision speed ≤30 km/h, the pedestrian head injury caused by the contact with the ground could be possibly more serious than the contact with the vehicle; while at the collision speed≥40 km/h, the pedestrian head injury was mainly caused by the contact with the vehicle. Conclusions The pedestrian traffic accident can be accurately reconstructed by using the real accident video to analyze the pedestrian head dynamic response. The severity of pedestrian head injuries can be effectively reduced by speed limitations on different types of vehicles at pedestrian traffic accident black-spots.
2013, 28(2):171-177. DOI: 10.3871/j.1004-7220.2013.2.177.
Abstract:Objective To establish a new trajectory tracking algorithm combined with trapezoidal velocity, so as to realize the trajectory control of the assistive standing-up robot and help subjects complete the standing-up training. Methods Forces of the assistive standing-up robot acting on subjects were analyzed by deducing the force and moment balance equations. According to the interpolation points of the target curve, trapezoidal velocity and current position points of the end-effector, the trajectory tracking algorithm of the assistive standing-up robot was developed, and a simulation platform was built up by Simulink/Stateflow software. Based on the established Xpc target and host computer, assistive standing-up robot and 3D motion analysis system, trajectory tracking of the straight line, curves in different shapes, standing-up curve of the subjects were tested. Parameters that affected the velocity and accuracy of trajectory tracking as well as the differences in trapezoidal velocity and standing-up velocity were discovered. Results Accurate positon control of the assistive standing-up robot was achieved by trajectory tracking algorithm. The standing-up trajectory curve and trapezoidal velocity could meet the requirement of standing-up velocity for the subjects and fulfill their requirements for different curve shapes and velocities. Conclusions The assistive standing-up robot using trajectory tracking algorithm combined with trapezoidal velocity can accurately track the target curves without limitation of curve shapes, and help the standing-up training for subjects. The established simulation and test platform in consideration of different subjects’ standing-up trajectory curve, velocity and accelaraion will assist standing-up more effectively.
2013, 28(2):178-183. DOI: 10.3871/j.1004-7220.2013.2.183.
Abstract:Objective To study the modeling method of rat model and the air flow characteristicwith its upper stenosis-airway. Methods Thirty-two 3-month old rats were randomly divided into two groups: the control group and the model group. For the model group, sodium hyaluronte of 0.1 mL was injected into mucosa of the soft palate and uvula in each rat under the anesthetic state. After feeding under the same condition for 3 months, CT scans and respiratory experimental examinations were performed on the two groups, respectively. The computational fluid dynamic (CFD) method was then employed to simulate the airflow in their upper airway. The flow characteristics were compared between the control rat and the model rat. Results (1) The minimum cross-sectional area of pharyngeal in the model group was reduced remarkably than that of the control group, showing that the airway of the model rats was significantly narrower than that of the control rats (P<0.05). (2) The model rats became breathless, and their respiratory period became unsteady. The breath intensity of the model rat on the pharynx fluctuated more rapidly. (3) The maximum wall shear stress on the pharynx of the control rat was scattered at the respiratory phase while it was concentrated for the model rat. Conclusions The injection of sodium hyaluronte into mucosa of the soft palate and the uvula can induced the narrowness of the upper airway in the model rat, which is similar to patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) in pathology. The narrowness of the upper airway can cause dyspnea and extend respiratory period. The shear stress on the pharynx of the upper stenosis-airway induces stronger damage to the pharynx tissue, especially to the soft palate and uvula, which aggravates reconstruction of the pharynx tissue.
2013, 28(2):184-188. DOI: 10.3871/j.1004-7220.2013.2.188.
Abstract:Objective To evaluate the influence of different insertion torque values on stress and strain distributions at implant-bone interface. Methods The three-dimensional finite element model of the whole mandible with dental implants for immediate loading was created by CT scanning and self-developed USIS (universal surgical integration system) software. The insertion torque values of dental implants were supposed to be 0、15、25 N?cm3, respectively. The values of Von Mises stress and strain at implant-bone interface were calculated with ANSYS software, when the dental implants were loaded with vertical and buccolingual force at a 45°oblique angle of 150 N. Results When the dental implants under the three insertion torques were loaded with the vertical force, the maximum Von Mises stress was 33.6, 56.4, 69.6 MPa and the maximum strain was 5 157, 8 645, 15 630 με, respectively, while loaded with the buccolingual force, the maximum Von Mises stress was 95.3, 100.6, 108.3 MPa and the maximum strain was 17 110, 18 690, 21 380 με, respectively. Conclusions With the increased torque value of dental implants, the stress and strain at the implant-bone interface were both increased, but the increase was much slower under buccolingual loading than that under vertical loading.
2013, 28(2):189-194. DOI: 10.3871/j.1004-7220.2013.2.194.
Abstract:Objective To investigate effects of pressure and tail suspension on the growth of rat skeletal muscles by establishing the tail-suspended rat model and pressure-induced rat model, respectively. Methods Thirty-six male Sprague-Dawley rats were randomly divided into three groups: the control-group (CON), the tail-suspended group (SUS), the pressure group (PRE), and each group was undergoing two stages (7, 14 d) for observation. At the end of the experiment, the muscle wet weight/body weight (Mww/Bw), muscle fiber cross-sectional area (MFCSA), muscle fiber diameter (MFD) of soleus and extensor digitorum longus (EDL) and the IGF-1 concentration were measured, respectively. Results For both the SUS group and PRE group with 7d, their Mww/Bw, MFCSA and MFD of soleus were significantly reduced (P<0.05) as compared to the CON group, which were reduced by 23.52%, 14.26%, 13.47% in PRE group, respectively , while these indexes in SUS group were reduced by 23.52%, 33.07%, 25.09%, respectively. Meanwhile, the decrease of Mww/Bw, MFCSA and MFD in PRE group with 14d was reduced by 20.51%, -10.49%, -5.73%, respectively, which was less than that in PRE group with 7d. However, the decrease of Mww/Bw in SUS group with 14d reached 46.15%, showing significantly higher than that of the SUS group with 7d. For the IGF-1 concentration and EDL changes, no remarkable differences were found among the CON, PRE and SUS groups. Conclusions The impact of pressure on the process of soleus growth is different from that of the suspension (disuse). During the early stage of pressure application, the deep tissue injury mainly with inflammatory responses can be found in the muscle. When the muscle cells adapt to the pressure environment, they may produce a functional adaptation to growth. Therefore, such effect of socket pressure on skeletal muscle should be considered in clinic for prosthetic socket design or rehabilitation training, which will help protect the muscle tissues.
2013, 28(2):195-200. DOI: 10.3871/j.1004-7220.2013.2.200.
Abstract:Objective To investigate the mechanical properties of both artificial cartilage and host cartilage by establishing the in vitro model of tissue engineered cartilage for repairing defects. Methods The agarose gel as an artificial cartilage was implanted in a deep cartilage defect connected with biological adhesive to set up the in vitro model of tissue engineered articular cartilage defects. Under the compression load, the instant mechanical behavior of the repair area was studied using the digital image correlation technology. Results There was no cracking phenomenon occurred at the interface during the compression process. The Strain distributions at middle layer of the repair area were obtained when the cartilage thickness appeared changes with 3.5%, 5.6%, 7.04% and 9.0% by the compression, respectively. When the compressing change increased from 3.5% to 9%, the maximum compressive strain of host cartilage was increased by 75.9%, and the maximum tensile strain of artificial cartilage was increased by 226.99% in the vertical direction of cartilage surface. In the direction parallel with cartilage surface, the maximum tensile strain at the interface was increased by 116.9%, and the increment was far more than that at the host cartilage area and artificial cartilage area. For shear strain at the repair area, the direction of shear strain at the interface changed oppositely with the compression increasing. Conclusions The repair effect of tissue engineered cartilage was uncertain due to the mechanical environment of the repair area. After the tissue engineered cartilage was implanted in the defect, the repair area was under the influence of complex strain states. The strains changed greatly at the interface both with the host cartilage and artificial cartilage as the compression increasing. The strain in the vertical direction of cartilage surface at the interface might change from compressive stain to tensile strain, which was significantly increased in the direction parallel with cartilage surface. The strain direction at the interface could even be changed oppositely, and the shear strain appeared rapidly increase. The complex strain states lead to such great changes in mechanical environment of the defect area, and may cause cracking at the interface, and even further affect the repair process. Therefore, attention should be given to this complex mechanical environment during cartilage defect repair process in clinical treatment.
2013, 28(2):201-209. DOI: 10.3871/j.1004-7220.2013.2.209.
Abstract:Objective To investigate the effect of hydrostatic pressure and estrogen on the proliferation, F-actin cytoskeleton, osteogenic and chondrogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs), and to test whether combined stimulation can exert the fortified stimulating effort on BMSCs． Methods BMSCs were separated by using the whole bone marrow culture method and purified by differential adherence method. BMSCs surface markers were detected by flow cytometer. BMSCs were randomly assigned to six groups：blank control group (Group C), 1 nmol/L 17β-Estradiol treatment group (Group E), 1 nmol/L tamoxifen treatment group (Group T), 90 kPa pressure treatment group for 1 h (Group P); 17β-Estradiol pretreatment for 12 h and 90 kPa pressure group for 1 h (Group P+E); and tamoxifen pretreatmet for 12 h and 90 kPa pressure group for 1 h (Group P+T). Cell cycle was measured by flow cytometry. Fluorescent staining under laser scanning confocal microscope observation was observed for F-actin cytoskeleton expression and re-assembly. After osteogenic differentiation for 7 d and 14 d, calcified nodules were detected with alizarin red staining. Further, the osteogenic markers including Col I, ON, OPN and BSP were analyzed by real-time PCR. Following chondrogenesis of BMSCs for 14 d and 28 d, proteoglycan contents were detected with toluidine blue staining, and chondrogenic markers including Sox9, Aggrecan and ColⅡwere evaluated by real time PCR. ANOVAs followed by the Dunnett t tests were adopted for comparisons among subgroups. All the experimental data were analyzed by SPSS 16.0 software. Results Both hydrostatic pressure (90 kPa, 1 h) and 1 nmol/L17β-estradiol could increase the proliferation of BMSCs and F-actin activation, but no bio-cooperation effects appeared. Calcified nodules were observed after 14 d osteogenic induction. Real-time PCR showed the estrogen enhanced osteogenetic gene (Col I, ON, OPN and BSP) expression in 7 d and 14 d. Combined effects of pressure and estrogen showed synergistic improving effects on early osteogenetic differentiation, but oppositional effects on advanced osteogenetic differentiation. Toluidine blue staining was positive after 28 d chondrogenic induction. With the hydrostatic pressure loading regime, the mRNA expression of chondrogenic genes (Sox9, Aggrecan and ColⅡ) was increased significantly, but with oppositional effects from estrogen on advanced chondrogenic differentiation. Conclusions The superposition effects of mechanical stimulation and estrogen acting only enhanced the differentiation of BMSCs in the early osteogenetic differentiation, but no effect was found in the proliferation and F-actin activation. Hydrostatic pressure and estrogen show antagonistic action in advanced osteogenetic differentiation and chondrogenic differentiation. Estrogen promotes osteogenetic differentiation, while hydrostatic pressure can enhance chondrogenic differentiation of BMSCs.
2013, 28(2):210-215. DOI: 10.3871/j.1004-7220.2013.2.215.
Abstract:Objective To make the stent expand uniformly along the axial, an improved kriging optimization algorithm is applied for to the optimal design of stent-balloon system to find the optimal length of the balloon. Methods Based on finite element method results, kriging surrogate model combining with Latin hypercube sampling (LHS) approach and expected improvement (EI) function was employed for the optimization of balloon length to reduce stent dog-boning effect during its dilation. Results The kriging surrogate model could approximately establish the relationship between stent dog-boning rate and balloon length and so to replace the expensive reanalysis of stent dilation. Sample points from LHS could perfectly represent the vector space. EI function could be used to effectively find out the global optimal solution with high probability. The optimal length of balloon could make the stent expand uniformly. Conclusions This adaptive optimization method based on kriging surrogate model can optimize the design of stent–balloon system effectively.
2013, 28(2):216-222. DOI: 10.3871/j.1004-7220.2013.2.222.
Abstract:Objective To investigate effects of pressure and tail suspension on the growth of rat skeletal muscles by establishing the tail-suspended rat model and pressure-induced rat model, respectively. Methods Thirty-six male Sprague-Dawley rats were randomly divided into three groups: the control-group (CON), the tail-suspended group (SUS), the pressure group (PRE), and each group was undergoing two stages (7, 14 d) for observation. At the end of the experiment, the muscle wet weight/body weight (Mww/Bw), muscle fiber cross-sectional area (MFCSA), muscle fiber diameter (MFD) of soleus and extensor digitorum longus (EDL) and the IGF-1 concentration were measured, respectively. Results For both the SUS group and PRE group with 7 d, their Mww/Bw, MFCSA and MFD of soleus were significantly reduced (P<0.05) as compared to the CON group, which were reduced by 23.52%, 14.26%, 13.47% in PRE group, respectively, while these indexes in SUS group were reduced by 23.52%, 33.07%, 25.09%, respectively. Meanwhile, the decrease of Mww/Bw, MFCSA and MFD in PRE group with 14 d was reduced by 20.51%, -10.49%, -5.73%, respectively, which was less than that in PRE group with 7 d. However, the decrease of Mww/Bw in SUS group with 14 d reached 46.15%, showing significantly higher than that of the SUS group with 7 d. For the IGF-1 concentration and EDL changes, no remarkable differences were found among the CON, PRE and SUS groups. Conclusions The impact of pressure on the process of soleus growth is different from that of the suspension (disuse). During the early stage of pressure application, the deep tissue injury mainly with inflammatory responses can be found in the muscle. When the muscle cells adapt to the pressure environment, they may produce a functional adaptation to growth. Therefore, such effect of socket pressure on skeletal muscle should be considered in clinic for prosthetic socket design or rehabilitation training, which will help protect the muscle tissues.
2013, 28(2):223-228. DOI: 10.3871/j.1004-7220.2013.2.228.
Abstract:Objective To study the effects of the various thickness of periodontal ligament on stress and displacement of mandibular first molar and periodontal tissues during mesial movement of tooth in lingual orthodontics. Methods Based on the reverse engineering technology, the three-dimensional assembly models of the teeth, periodontal ligament and alveolar bone with the same height of alveolar bone were constructed, and thicknesses of the periodontal ligament was 0.15, 0.2, 0.25, 0.3 and 0.35 mm, respectively. The stress and displacement of periodontal ligament, root and surface of alveolar bone were analyzed under the condition of lingual tipping, rotation and translation movements. Results For the maximum stress of periodontal ligament, root and surface of alveolar bone due to different periodontal ligament thickness, the ratio of the maximum value to the minimum value was 1.46, 2.06 and 6.72, respectively. For the maximum displacement of root and the surface of alveolar bone, the ratio of the maximum value to the minimum value was 1.65 and 1.50, respectively. Corresponding with different thickness of periodontal ligament, the location of the maximum stress of root and periodontal tissues would change at root, periodontal furcation and tooth neck. Conclusions In clinical practice, changes of tooth neck, periodontal furcation and root should be observed carefully, and the translation movement is more conducive to the health of teeth and periodontal tissues for patients with thin thickness of periodontic ligament.
2013, 28(2):229-234. DOI: 10.3871/j.1004-7220.2013.2.234.
Abstract:Objective To visualize the process of introcular flow caused by injection into the posterior chamber of the impermeable vitro eyeball with particle image velocimetry (PIV) technology, and calculate the flow fields at different moments, so as to investigate PIV experimental scheme for low-speed flow field measurement in the eye and provide basis for the in vivo measurement of aqueous humor flow under physiological status. Methods In an impermeable vitro eyeball, the introcular flow would be slow enough when the injection pump was driven at the rate of 0.2, 0.4, 0.6, 0.8, 1.0, 1.5 mL/min. Fluorescent particle solution, with a certain concentration and particle diameter of 10 μm, was injected into the posterior chamber of the vitro rabbit eye, and the sheet laser was projected to the medial frontal plane of the eye. Then clear particle images were captured by camera, and the velocity field was recorded and calculated by PIV system. Results The fluid into the posterior chamber first filled in the posterior chamber and the pupil, then passed the pupillary margin and flowed into the anterior chamber, which was consistent with the theoretical flow process of aqueous humor under physiological conditions. Based on analysis of the particle images, the velocity inside an impermeable eyeball was calculated at the magnitude of a few millimeters per second. Conclusions PIV method can be applied to low-speed flow field measurement, and the flow characteristics inside the eyeball can also be measured by PIV method, which contributes to the measurement of aqueous flow under both physical and pathological conditions, provides experimental verification for numerical simulations on aqueous humor field, and offers a new diagnostic and treatment perspective for shear force damage and destructions of corneal endothelial cells, the iris and lens under different flow fields.
2013, 28(2):235-239. DOI: 10.3871/j.1004-7220.2013.2.239.
Abstract:Objective To investigate the biomechanical stability of both DHS (dynamic hip screw) and PFN (proximal femoral nail) for treating unstable intertrochanteric fractures. Methods A standard 4-part osteotomy was performed in 8 pairs of fresh frozen human cadaver femurs, which were then randomly assigned to two groups: PFN group and DHS group for biomechanical testing. These specimens were applied to a cyclic load up to 200, 400, 600, 800, 1 000, 1 200, 1 400 N, respectively. Fracture displacement was measured during the loading to determine biomechanical stability of the implant. Each specimen was repeatedly loaded for 5 times to calculate the average displacement and draw the load-displacement curve. For failure testing, the initial load and loading rate was set at 1 400 N and 10 N/s, respectively. The applied compressive load was increased by 600 N each time for five cycles. The pressure was gradually increased to its peak force, and sustained for 10 second before it was gradually decreased to 0 N. The highest force value sustained before failure was defined as the maximum strength of the implant. Results The biomechanical testing on all specimens was completed successfully. There was no damage to the internal fixation. The average displacement and stiffness in DHS group were (3.92±2.21) mm and (215.28±58) N/mm, while those in PFN group were (4.22±1.80) mm and (197.06±34.20) N/mm, so no significant difference was found between the DHS and the PFN group (P> 0.05). New fracture occurred at the distal end of nail in PFN group. The DHS was fractured at the distal cortical screw, but no nail was cut out of the femoral head. The average load required for failure was (4 312±560) N in PFN group and (3 954±520) N in DHS group, and no significant difference was found between the two groups(P＞0.05). Conclusions The test shows that the PFN does not appear to offer any distinct biomechanical advantage over the DHS in the treatment of unstable intertrochanteric fractures. The implant chosen for treating intertrochanteric fractures must depend on patient’s fracture geometry, and anatomic reduction should be conducted in clinical treatment. If the anatomic reduction is difficult, trying to recover continuity of the posterior cortical bone would be necessary.
2013, 28(2):240-244. DOI: 10.3871/j.1004-7220.2013.2.244.
Abstract:High flexion of the knee is very common for some specifically occupations and daily activities in many Asian and Mid-East countries. The major ligaments, including anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, lateral collateral ligament and joint capsule, are the most important static structures with function to maintain stability of the knee. Therefore, a thorough understanding on biomechanics and kinematics of the major knee ligaments at high flexion angles is significant in treatment of soft tissue release during total knee arthroplasty, anatomical cruciate ligament reconstruction and rehabilitation of knee disorders. In this paper, the research methods on knee biomechanics in recent years, and the biomechanical properties of the static knee structure from stretching to high flexion are reviewed. The further aim of the research direction in soft tissue balance during total knee arthroplasty, repair and reconstruction of knee ligaments, postoperative rehabilitation after knee injuries in the future are predicted.