Abstract:Orthopaedic biomechanics means to apply biomechanics methods to resolve clinical problems in orthopaedics, especially when mechanical principles are used, lots of problems unsolved could be ravel out. For instance, the design and clinical application of artificial joint replacement with the help of biomechanics can ease the patients' pain suffering from degenerative arthritis. 11 papers related with orthopaedics biomechanics published in this special issue involve in the study on tissue engineering, sports medicine, spine and artificial joints from both the clinical application and basic research with the methods of material testing machines and finite element analysis by computer. These articles could help readers understand how mechanics is used in orthopaedic research and hope to encourage them to find more issues suitable to use orthopaedics biomechanics to research in the clinic practice.

Abstract:Objective This study analyzed the UHMWPE insert wear in total hip replacement of different prosthesis designs and wear conditions. Methods Specimens of acetabular cups were selected among the total hip prosthesis revisions at Mackay Memorial Hospital, Taipei, during the years from 1993 to 2003. The specimens included products of DePuy-AML? Plus series, Mecron-Mecring series and Osteonics-Omnifit series, which were of totally different designs. This study focused on differentiating the wear among these three types of products. In our study, the wear score was defined as the severity factor (determined by the wear pattern) × the amount present (determined by the worn area). The number was multiplied by a severity factor assigned to each wear pattern on a scale of 0-7. A classification system was designed which identified the following eight pattern of damage on the surface: burnishing, abrasion, deformation, scratching, pitting, delamination, wear-through and component fracture. In each region the severity of each pattern was graded on a scale of 0-3, based on the percent area of the region affected, to give a total cumulative wear score for each UHMWPE insert. We inspected the UHMWPE insert with light stereomicroscopy to measure worn area and to classify the wear pattern. The wear scores thus calculated were analyzed to demonstrate the difference in wear related to designsof components in the types of hip prostheses. Results The most common types of wear observed, abrasion (100%), wear-through, component fracture (40%), scratching (36%) and burnishing (33%). Multiple linear regression analysis was used to determine possible associations between wear score and the patient’s gender, age and weight at the time of the operation, the duration that the implant had been in situ. It was found no relationship between any clinical variable and the visually evaluated wear score. There was a significant positive correlation between the wear score and the angle of the inclination of the cup. Conclusion Clinical variables have little influence on polyethylene wear of well functioning hip replacements. Alternatively, it may be related to the variety of cup designs included in our study.

Abstract:Objective To develop a three-dimensional (3D) comprehensive finite element (FE) foot model for studying the biomechanical effects of different parametrical designs with various foot orthoses, soft tissue stiffness and loading conditions. Methods Based on the accurate anatomical structures including the encapsulated soft tissue, ligaments and plantar fascia, and taking the nonlinear properties of material and foot contacting into consideration, a 3D FE mode of foot was developed. The reliability and validity of the FE model to quantify the biomechanical response of the foot and ankle under different simulated pathological, surgical and orthotic conditions were investigated. Results The FE analysis showed that such a custom-molded shape was more important for relieving of the plantar peak pressure than the stiffness of orthotic material as far as the design is concerned. Increasing soft tissue stiffness would lead to decrease the total contact area of the foot-support interface and then make the increases in plantar peak pressure of the bony prominences. Either reducing the stiffness of plantar fascia or surgical releases of the partial or the entire plantar fascia could decrease the arch height, increasing the strains of the plantar ligaments and intensifying the stresses in the midfoot and metatarsal bones. The FE predictions showed that both the increase of weight on the foot and achilles tendon loading resulted in an increase in tension of the plantar fascia with the latter showing a two-times larger straining effect. Conclusion The established FE model, which allowed prediction of plantar pressure distributions as well as the internal stress and strain of the bony and soft tissue structures, can be an effective tool to study different clinical questions and for footwear design.

Abstract:Objective Good coverage of tibial component and proximal resected tibial surface can improve the strength of component fixation and thus avoid component subsidence and loosening. Most prostheses used in Taiwan are imported from USA or Europe. Such tibial components don’t have good coverage for Taiwanese in our previous study. Especially in revision knee surgery, the shape is varied in different cutting thicknesses of the tibia, which makes it more difficult to have a good coverage of revision tibial component and resection surface. The purpose of this study was to investigate the proximal tibial morphology of Taiwanese. The results can be applied for geometric designs of tibial baseplate and augmentation. Methods Fifty osteoarthritis knees were collected for analysis. Three-dimensional proximal tibia was constructed from Computed-Tomography slices for measuring morphologic data. Five cutting depths of 4, 7, 10, 13, and 16mm below tibial plateau were measured. The parameters included the dimensions of anteroposterior length (AP), mediolateral width (ML) of resected surface and four radii as anterolateral radius (AL), posterolateral radius (PL), anteromedial radius (AM), and posteromedial radius (PM). Results The results showed that mean AP was 47.4mm(40.4-52.9), mean ML was 69.0mm (59.6-79.1), AL was 30.0 mm (18-38), PL was 20.0 mm (10-25), AM was 28.7 mm (18- 36), and PM was 17.9mm (11-23). Conclusion Comparing the results with commercial tibial components, the imported implants of PFC sigma and Zimmer Nexgen could provide better coverage for Taiwanese. Body height and dimensions of AP and ML present high dependence, and American and European is relatively taller than Taiwanese. The factor of body height may highly influence the covering rate of tibial components. This study suggested 5 sizes of tibial components for Taiwanese. They can improve the rate of coverage, and reduce the rate of implant subsidence.

Abstract:Objective To analyze and compare the application of different modeling methods used in the construction of bio-tissue 3D finite element model. Methods: Based on the same serial CT images, to construct calcaneus 3D finite element model with the implementing of three different methods (direct, indirect, and composite methods), then to carry out simple loading calculation on two models under the same condition. Results The number of nodes and elements generated from direct modeling are 31386 and 115646, while that from indirect modeling are 22832 and 15403, respectively; and that of composite method are 13050 and 46654, respectively. The results reveal the similar distributing of von Mises Stress of three models, with some local differences, but the special stress values show greater difference. Conclusion The exterior roughness of model and the form of material assignment have great effect on the calculating result of models. Different modeling method has their own appropriate application fields. For the purpose of medical research, it would be better to combine the two methods to promote the development of computational biomechanics.

Abstract:Objective To obtain the normal linear parameters on the different resection levels of normal proximal tibia in Chinese, and provide reference for improving the design of domestic knee prosthesis and clinic technology of TKA. Method Choose 61 normal Chinese (100 knees, include 65 male and 35 female knees), with average age of 47.2 years (range from 1 7 to 81 year-old), Then divided them into groups according to the age, side of the knee and gender. Utilized original CT image data to set up the three-dimensional model of Chinese normal knees and measure the related linear parameters of different proximal tibia sections on the work station. Result The average anterior-posterior (AP) and medial-lateral (ML) lengths of the proximal tibia section were 48.9±3.1 and 75.2±4.5mm, respectively; the ratio of anterior- posterior (AP) and medial-lateral (ML) was 0.650±0.034. the average anterior-posterior dimensions through the spots with 10, 20 and 30% were 36.1, 46.6, 51.2, 37.1, 44.1 and 47.6 mm, respectively; It is confirmed through statistics analysis that the length of AP and the ratio of AP/ML shows statistics significance among different gender and resection level. Conclusion The geometry and anatomy of proximal tibia in Chinese shows significant differences comparing with westerner; the characteristics and the gender difference should be considered when we use the tibial plateau prosthesis designed by the westerner; the sex difference should also be taken into account when we design the domestic tibial plateau prosthesis and total knee arthroplasty.

Abstract:Objective To introduce a 4 quadrant zoning method measuring dynamic force distribution of multi-bundle fibers in anterior cruciate ligament (ACL) to find out the mechanical relationship between tibial footprint and force distribution of ACL multi-bundle fibers. Methods A cadaveric study was performed with 8 normal Chinese human knees. After the integrity evaluation of each specimen d, the tibial insertion site of ACL was detached from plateau through a tibial tunnel. The footprint was averagely separated into 4 zones according to sagittal plane and coronal plane as zone 1 (posteromedial zone), zone 2 (posterolateral zone), zone 3 (anterolateral zone) and zone 4 (anteromedial zone). Fibers were also separated into 4 bundles according to each attached zone and linked to the custom-made force transducers. Zero strain was set to all bundles at 90o and 0o respectively and forces of each bundle were measured during 0-120o of knee cyclic motion in four degree of freedom (DOF) of knee joint during flexion and extension. Results The forces measured from zone 2 and 3 increased during extension. The max force of zone 2 reached 22.52±8.60N (30o) and thatof zone 3 reached 13.98±3.47N (0o). Forces of zone 3 and 4 increased during flexion. The max force of zone 3 was 9.84±5.06N (60o) and that of zone 4 was 14.68±5.29N (90o). Forces in all fibers increased during the valgus, rotation and anterior drawer tests. Force distribution in zone 1 did not change in most DOF of knee. Conclusion The fibers attached to the posterolateral zone contributes to the largest restraint of anterior tibial translation. While the anteromedial zone plays the most important role during knee flexion. The anterolateral zone contains the fibers functioning as linkage during flexion and extension, so it can be regarded as the transient fiber of ACL during movement. In this study, we found that 4 quadrant zoning method of ACL tibial footprint helps to learn the continuous dynamic force distribution of ACL multi- bundle fibers, and provide the basic parameters for further study.

Abstract:Objective To investigate the solid-fluid coupling problem in vertebra and intervertebral disc under concentrated loading force. Methods The vertebra and intervertebral disc are considered as porous material, consisting of solid skeleton and pore fluid. Biot equations are used to describe the solid-fluid coupling behavior for vertebra and intervertebral disc. The equilibrium equations and continuum equation were built in axisymmetric forms while the integral forms are derived by weights residual methods. The FE procedure is programmed in FROTRAN to simulate the coupling behavior for vertebra and intervertebral disc. Results The pore-pressure decreases while the displacement increases, both gradually tend to be balanced as time goes by, with higher value in the central area of disc compared with the surrounding ones. Conclusion It showed that external loads obviously affect that pore-pressure and displacement with the present numerical results according with the existing data.

Abstract:Objective To investigate the effect of posterior pedicle screw instrumentation and determine the impact of alternative surgical strategies to provide guidance for the operation planning. Methods A detailed three-dimensional finite element model of a 40° scoliotic lumbar with pedicle screw instrument were constructed by using the commercial finite element software ANSYS. The geometry of the model was extracted from a computed tomography reconstruction. The correction process including rod rotation and spring-back was simulated with rigid body dynamic software ADAMS. Reaction loads on implant as well as stress distribution of lumbar spine were acquired through the correction simulation. Results The maximal reaction forces were in the range of 196-1099 N. Few bony elements around the screw exceeded the ultimate strength of 120 MPa. Conclusions Idiopathic scoliosis could be well treated by posterior pedicle screw instrumentation with the safety of vertebrae ensured. Different surgical strategies could be considered to conserve implanted lumbar spine level and to improve the surgical quality.

Abstract:Objective To investigate the relationship between cell proliferation and β-tubulin of rabbit articular chondrocytes under intermittent tension. Methods Chondrocytes were cultured in monolayer on flexible substrates and subjected to cyclic strain 0-5% with sinusoidal waveforms at 0.5 Hz for 3h/ day over 3days by using FX-4000TTM unit. Cell viability, extracelluar matrix, β-tubulin immunofluorescence and cell cycle were measured respectively. Results The cell viability and extracelluar matrix tests showed that articular chondrocytes cultured in monolayer grew well in vitro. There was no difference in the extracellular matrix synthesis between the loaded group and control group. However, the cell proliferation index increased significantly under intermittent tension. Furthermore, cultured chondrocytes underwent significant morphological changes when subjected to intermittent tensile stress. The cells elongated and aligned in a certain direction. Accompanying this shape change was a reorganization of β-tubulin in the direction of the cells’ long axis. Conclusion Our findings suggest that intermittent tension may have an active effect on the cell growth, and β-tubulin of articular chondrocytes plays an important role in the transduction of intermittent tensile stress which cause reorientation of articular chondrocytes.

Abstract:Objective To establish a 3D culture model of chondrocytes within agarose gel and evaluate the mechanical properties of the chondrocyte-agarose disks. Methods Chondrocytes were mixed with agarose, serum and medium to form engineered cartilaginous constructs. At the 7th day, 14th day and 21st day, the constructs were removed respectively from the culture plates, and stained with Safranin-O for sulfated glycosaminoglycan or Toluidine Blue for proteoglycans or labeled using antibodies against collagen types II. The mechanical properties of ultimate stress, strain, Young’s modulus and tangent modulus were assessed using Instron5544 machine at the same time. Result Agarose gel was found to provide a good microenvironment for formation of extracellular matrix. In addition, it could construct mature and mechanical properties depended on the culture time. At the 21st day, experimental studies have shown that ultimate stress, Young’s modulus, tangent modulus(0.0226±0.006, 0.608±0.061, 0.096±0.004) exhibited a higher value compared with that of 7th day (0.0204±0.004, 0.558±0.036, 0.029±0.002) and14th day (0.0213±0.008, 0.586±0.095, 0. 049±0.005), but there is no significantly difference in ultimate strain (P>0.05). Conclusion The mechanical properties of chondrocytes/agrose disks depend directly upon the extracellular matrix surrounding the cells.

Abstract:Objective To establish a human elbow joint dynamical modelling in the sagittal plane and seek for an impactful way for solution. Methods To use the optimization toolbox of Matlab for optimizing and solve the modelling. Results The muscle contraction, joint reaction and their corresponding moments were obtained when different external force was applied to the forearm at different elbow joint angle velocity, and it shows that the results are good agree with the literatures. Conclusions The optimization toolbox of Matlab can be used to solve this kind of questions reasonably and the modelling can be used to calculate the muscle contraction, joint reaction and their corresponding moments at the human elbow joint under the application of different external force.

Abstract:Objective To explore the relation between the biochemical stimulus and big deformation during cytokinesis in eukaryotes. Methods Basis on many experiment data, A new model is proposed in this study to simulate the entire process by coupling the biochemical stimulus with the mechanical actions based on Zinemanas and Nir ’s hydrodynamic model. There were three assumptions in this model, ie. the movements of phospholipid proteins are driven by gradients of biochemical stimulus on the membrane surface, the local assembly of actin and myosin filament lies on the amount of phospholipid proteins at the same location, and the surface tension includes membrane tensions due to both the passive deformation of membrane and the active contraction of actin filament which is determined by microfilaments redistribution and rearrangement. Results These calculated results from this model showed that the contractile ring formed on early, microfilaments and the cell deformation dynamical varied during cytokinesis. Conclusion The model demonstrated that the reorientation of phospholipid proteins and the redistribution and reorientation of microfilaments may play a crucial role in cell division. This model may better represent the cytokinesis process by the introduction of biochemical stimulus.

Abstract:Objective Real-time three-dimensional echocardiography (RT3DE) is an important method for heart hemodynamics research. Traditionally the whole research process has to divide to the following two phases: firstly render the heart full-volume data from RT3DE and then find the optimal cutting planes of it with manual operation. Such procedure not only spent too much time but also difficultly to handle. Now, the new method could be used to implement the extraction on personal computer automatically. Methods With the help of the video card with graphic processing unit, we reconstruct the 3D image of the heart based on personal computer and demonstrate the improved entropy for the optimal cross section selection with correlation coefficient method. Results We have completed the whole process in C/C++, with the help of OpenGL Library. We also add some segment into the program to speed up the hardware with Cg language on GPU (Graphics Processing Unit). Conclusion This new method could satisfy the doctor's clinical need with the better veracity and higher cartography speed.

Abstract:Objective To find out accurate resonance frequency and vibration characteristic of mouse liver in low frequency as the research base for resonance trauma and its reaction on organs. Methods Seventeen male mice were anaesthetized in abdominal cavity with 1.5% sodium pentobarbital and their livers were pasted with sensors. Nine of them were fastened on vibration platform to be sweeping-frequency vibrated. The frequency which is corresponding to the biggest amplitude is the resonance frequency. The other eight mice were fastened on the platform hung horizontally by rubber band. To hammer the veneer from the down to the top, and the biggest value of frequency spectrum is the resonance frequency. Results The resonance frequency of mouse liver in chest-back direction is 3Hz by the method of vibration from 2Hz to 49Hz, and the amplitude of vibration from 2Hz to 7Hz is higher than 50% of maximum amplitude. And the result obtained by hammer method is also 3Hz. Conclusion Both the vibration method and hammer method can accurately measure resonance frequency of mouse liver, and the method can also be used to measure resonance frequency of mouse’s other organs and other animals organs. The vibration method can measure vibration characteristic of a frequency range, but the hammer method can only measure the vibration characteristic near the range of resonance frequency.

Abstract:Objective A new method is used to describe the structure of biological tissue, and research the mechanical character of collagen fibre in the tissues. Methods A wormlike chain model is applied to capture the behavior of the collagen microfibrils. On the microlevel, the model used is basing on the statistics of long chain molecules; and on the macrolevel, the network of collagen chains is represented by a transversely isotropic eight chain unit cell introducing one characteristic material axis. Results At that event, the worm like chain model is chosen to analyse the mechanics character of biological tissue structure, and we get the force vs. elongation response curves of the wormlike chain model with anisotropy in an eight chain unit cell. Conclusion The eight chain unit cell has scaling and loading angle sensitivity. If the present model is governed by a limited number of physically motivated material parameters, it is believed to be ideally suited to simulate not only the passive behavior of soft biological tissues but also their active response to changes in the mechanical loading environment.

Abstract:Objective To analyze the interrelation between fat distribution feature inside vertebrae and its biomechanics feature through observing fat distribution feature inside vertebrae of health adult and associated it with the researched results of biomechanics feature of vertebral. Method This study include 56 health adult’s MR imaging material of T11- L5,we divided every vertebrae into 16 area, observed and noted the signal intensity of every area, made statistical analysis to the incidences of hyper-intensity signal among different area. At last, compare the study results to the biomechanics feature inside vertebrae researched. Results The incidences of hyper-intensity signal in different area are obviously different, it is the highest in Pedicle of vertebral arch (98%); the incidence in marginal (92%) is higher than it in intermedius (69%) in post-superior border, but the incidence in intermedius (50%) is higher than it in marginal (9%) in post-inferior border, there is no hyper-intensity signal distribution in anterior border and a few of signal distribution under end-plate (16%). The results of statistics analysis showed the difference of incidence in different area have obviously significance except it between the marginal in post-inferior border and under end-plate (P>0.0033). Conclusion The incidences of hyper-intensity signal in pedicle of vertebral arch and in post-superior border are obviously higher than other areas in vertebrae, both area bear the greatest stress in vertebrae according to the biomechanics study results.

Abstract:Knee is one of the biggest and most complicate joint in human body. With the development of the knee surgery, It is a trend for researching the medial collateral ligament in the future that how to attain the functional anatomy and biomechanics quantifiable characteristic. The research of the medial collateral ligament functional anatomy focus on: how to maintain the stability of the knee、how to limit the external rotation of the tibia、the difference of the stress location in MCL when knee bend 、rotate and walking. The research of the medial collateral ligament biomechanics focus on: content、linearity hardness、viscoelastic properties,etal. This paper reviewed recent advancements on the study of medial collateral ligament functional anatomy and biomechanics, especially on the quantifiable characteristic.

Abstract:Bone tissue has complex structure and biological system. The history of bone remodeling theory experiences three main periods: qualitative analysis, quantitative analysis and fix quantify value simulation by computer. Nowadays, there are two common bone remodeling models based on mechanical approach and phenomenological approach respectively. The mechanical model has the same basis that the apparent density is designed as a direct response to a certain mechanical stimulus. Otherwise, the phenomenological model is largely dependent on Basic Multicellular Units (BMU) damage and porosity change. Most of remodeling methods are isotropic, which does not denote constitutive relation of bone microstructure. This paper has reviewed bone remodeling criteria in Numerical Simulation.