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A high prevalence of middle one-third clavicle fracture has been reported. Both superior and anterior clavicle plates have been used in clinical and biomechanical research, but no decisive advantage for either design has been reported. Spiral clavicle plates have not been well studied in terms of their structural stability and implant safety. The present study analyses the multi-directional biomechanical performance of spiral clavicle plates using the finite element method. Two commercial spiral clavicle plate designs were reconstructed to simulate the surgical reduction of a middle one-third oblique clavicle fracture (OTA classification: 15-B1.2). Mechanical load, including axial compression, inferior bending, and axial torsion, was applied to evaluate the multi-directional structural stability and implant safety of the plates. The two spiral clavicle plate designs enhanced structural stiffness under axial compression, inferior bending, and axial torsion by 59–71%, 38–82%, and 31–46%, respectively, compared to that of the intact clavicle model. Stress concentrations were found around the reconstruction feature of the plate and the screw hole, especially under inferior bending. The improvement in multi-directional biomechanical stability provided by a spiral clavicle plate is worth considering in clinical applications. Implant safety should be further investigated based on mechanical tests and clinical observations.

The application of cold atmospheric plasma to titanium surface modification has recently become a research focus in the area of material modification. Previous studies found that cold atmospheric plasma can affect the colonization of bacteria and biological behaviors of osteoblasts by changing the surface characteristics of titanium in vitro. In vivo studies reveal that cold atmospheric plasma can promote the process of osseointegration of titanium implants. This review focuses on research on the effects of the surface modification of titanium implants with cold atmospheric plasma on osseointegration.近年来，低温等离子体应用于钛表面改性成为材料改性的研究方向之一。体外研究发现它通过改变钛表面性质，对细菌的定植和成骨细胞的生物学行为等产生影响。体内研究表明低温等离子体改性能促进钛种植体的骨结合过程。本文就低温等离子体改性钛种植体表面影响骨结合的体内外研究现状作一综述。.

Antibiotic-loaded polymethyl methacrylate (PMMA) has been widely applied in the treatment of knee periprosthetic joint infections. However, problems with antibiotic-loaded PMMA-based spacers, such as structural fracture and implant dislocation, remain unresolved. A novel polyethylene-based spacer, designed with an ultra-congruent articulating surface and multiple fenestrations, was introduced in the current study. Validation tests for biomechanical safety, wear performance, and efficacy of antibiotic cement were reported. During cycle fatigue testing, no tibial spacer failures were observed, and less wear debris generation was reported compared to commercial PMMA-based spacers. The volumetric wear of the novel spacer was within the safety threshold for osteolysis-free volumetric wear. An effective infection control was demonstrated despite the application of lesser antibiotic cement in the 30-day antibiotic elution test. The tube dilution test confirmed adequate inhibitory capabilities against pathogens with the loaded antibiotic option utilized in the current study. The novel polyethylene-based knee spacer may offer sufficient biomechanical safety and serve as an adequate carrier of antibiotic-loaded cement for infection control. Further clinical trials shall be conducted for more comprehensive validation of the novel spacer for practical application.

In the implementation of robot motion control, it often requires complex forward and inverse kinematics calculation. However, this algorithm requires more CPU time in the software realization and apparently affects the response of robot movement. To solve this problem, the work is aimed at the development of the forward and inverse kinematics IP (intellectual property) based on FPGA (field programmable gate array) implementation and hoped to complete the overall computation less than ten microseconds for the purpose of enhancing the performance of the robot movement. In this paper, firstly, the forward and inverse kinematics for SCARA robot is derived. Secondly the circuit behavior using VHDL (Very-High-Speed-IC Hardware Description Language) is described. The design of VHDL code will apply the parameterized function to increase the code flexible and the FSM (Finite state machine) strategy is used to reduce the hardware resource usage. To verify the correctness of the proposed forward and inverse kinematics IP, a co-simulation work is constructed by ModelSim and Simulink. The forward and inverse kinematics IP is run by ModelSim and the Simulink models is taken as a test bench that generates stimulus to ModelSim and displays the output response. Finally, the developed forward and inverse kinematics IP will be downloaded to FPGA to further confirm its effectiveness.

This paper investigates digital implementation issues on high speed permanent magnet (PM) machine drives. The machine operating speed is designed beyond 30krpm where the ratio of controller sample frequency $\mathrm{f}_{\mathrm{s}\mathrm{a}\mathrm{m}\mathrm{ple}}$ over rotor electrical frequency $\mathrm{f}_{\mathrm{e}}$ is less than 5. Because microcontrollers are used in variable frequency drives to realize the field oriented control (FOC), the discretized effects must be considered to maintain the controller stability under low ratios of $\mathrm{f}_{\mathrm{s}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{e}}/\mathrm{f}_{\mathrm{e}}$ . In this paper, the FOC based on different current controllers are compared specifically at low $\mathrm{f}_{\mathrm{s}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{e}}/\mathrm{f}_{\mathrm{e}}$ . It is shown that current controllers using forward difference and bilinear approximation are able to maintain the drive stability if the voltage delay and indcutance cross-coupling are compensated. However, the drive performance strongly depends on the accuracy of inductance parameter. By contrast, the controller using direct digital design achieves the better FOC performance independent to machine specifications. In this paper, different types of controllers are experimentally compared to find a suited high speed FOC drive.

Background Locking plate fixation for proximal humeral fractures is a commonly used device. Recently, plate breakages were continuously reported that the implants all have a mixture of holes allowing placement of both locking and non-locking screws (so-called combi plates). In commercialized proximal humeral plates, there still are two screw hole styles included “locking and dynamic holes separated” and “locking hole only” configurations. It is important to understand the biomechanical effect of different screw hole style on the stress distribution in bone plate. Methods Finite element method was employed to conduct a computational investigation. Three proximal humeral plate models with different screw hole configurations were reconstructed depended upon an identical commercialized implant. A three-dimensional model of a humerus was created using process of thresholding based on the grayscale values of the CT scanning of an intact humerus. A “virtual” subcapital osteotomy was performed. Simulations were performed under an increasing axial load. The von Mises stresses around the screw holes of the plate shaft, the construct stiffness and the directional displacement within the fracture gap were calculated for comparison. Results The mean value of the peak von Mises stresses around the screw holes in the plate shaft was the highest for combi hole design while it was smallest for the locking and dynamic holes separated design. The stiffness of the plate-bone construct was 15% higher in the locking screw only design (132.6 N/mm) compared with the combi design (115.0 N/mm), and it was 4% higher than the combi design for the locking and dynamic holes separated design (119.5 N/mm). The displacement within the fracture gap was greatest in the combi hole design, whereas it was smallest for the locking hole only design. Conclusions The computed results provide a possible explanation for the breakages of combi plates revealed in clinical reports. The locking and dynamic holes separated design may be a better configuration to reduce the risk of plate fracture.

The far cortical locking (FCL) system, a novel bridge-plating technique, aims to deliver controlled and symmetric interfragmentary motion for a potential uniform callus distribution. However, clinical data for the practical use of this system are limited. The current study investigated the biomechanical effect of a locking plate/far cortical locking construct on a simulated comminuted diaphyseal fracture of the synthetic bones at different distance between the plate and the bone. Biomechanical in vitro experiments were performed using composite sawbones as bone models. A 10-mm osteotomy gap was created and bridged with FCL constructs to determine the construct stiffness, strength, and interfragmentary movement under axial compression, which comprised one of three methods: locking plates applied flush to bone, at 2 mm, or at 4 mm from the bone. The plate applied flush to the bone exhibited higher stiffness than those at 2 mm and 4 mm plate elevation. A homogeneous interfragmentary motion at the near and far cortices was observed for the plate at 2 mm, whereas a relatively large movement was observed at the far cortex for the plate applied at 4 mm. A plate-to-bone distance of 2 mm had the advantages of reducing axial stiffness and providing nearly parallel interfragmentary motion. The plate flush to the bone prohibits the dynamic function of the far cortical locking mechanism, and the 4-mm offset was too unstable for fracture healing.

Pedicle screws are widely utilized to treat the unstable thoracolumbar spine. The superior biomechanical strength of pedicle screws could increase fusion rates and provide accurate corrections of complex deformities. However, osteoporosis and revision cases of pedicle screw substantially reduce screw holding strength and cause loosening. Pedicle screw fixation becomes a challenge for spine surgeons in those scenarios. The purpose of this study was to determine if an expandable pedicle screw design could be used to improve biomechanical fixation in osteoporotic bone. Axial mechanical pull-out test was performed on the expandable, conventional and augmented pedicle screws placed in a commercial synthetic bone block which mimicked a human bone with severe osteoporosis. Results revealed that the pull-out strength and failure energy of expandable pedicle screws were similar with conventional pedicle screws augmented with bone cement by 2 ml. The pull-out strength was 5-fold greater than conventional pedicle screws and the failure energy was about 2-fold greater. Besides, the pull-out strength of expandable screw was reinforced by the expandable mechanism without cement augmentation, indicated that the risks of cement leakage from vertebral body would potentially be avoided. Comparing with the biomechanical performances of conventional screw with or without cement augmentation, the expandable screws are recommended to be applied for the osteoporotic vertebrae.

Purpose– The inverse kinematics in robot manipulator have to handle the arctangent and arccosine function. However, the two functions are complicated and need much computation time so that it is difficult to be realized in the typical processing system. The purpose of this paper is to solve this problem by using Field Programmable Gate Array (FPGA) to speed up the computation power.Design/methodology/approach– The Taylor series expansion method is firstly applied to transfer arctangent and arccosine function to a polynomial form. And Look-Up Table (LUT) is used to store the parameters of the polynomial form. Then the behavior of the computation algorithm is described by Very high-speed IC Hardware Description Language (VHDL) and a co-simulation using ModelSim and Simulink is applied to evaluate the correctness of the VHDL code.Findings– The computation time of arctangent and arccosine function using by FPGA need only 320 and 420 ns, respectively, and the accuracy is Practical implications– Fast computation in arctangent and arccosine function can speed up the motion response of the real robot system when it needs to perform the inverse kinematics function.Originality/value– This is the first time such to combine the Taylor series method and LUT method in the computation the arctangent and arccosine function as well as to implement it with FPGA.

A cross-coupled proportional-integral-derivative neural network (PIDNN) control is proposed in this study for the synchronous control of a dual linear motors servo system which is installed in a gantry position stage. First, the dynamics of the field-oriented control PMLSM servo drive with a lumped uncertainty, which contains parameter variations, external disturbance and friction force, is introduced. Then, to achieve accurate trajectory tracking performance with robustness, an intelligent control approach using PIDNN is proposed for the field-oriented control PMLSM servo drive system. In the proposed approach, the on-line learning algorithms of the PIDNN are derived using back-propagation (BP) method to guarantee the convergence of the network. Finally, some experimental results are illustrated to depict the validity of the proposed control approach.

SummaryInterference screw fixation is one of the most common methods for ligament reconstruction. Although the advantages and clinical outcomes of this procedure have been widely reported, post-surgical complications often arise. The purpose of this study was to evaluate a new femoral fixation device, the Endoscrew, for anterior cruciate ligament (ACL) reconstruction. We performed a mechanical test in accordance with American Society for Testing and Materials (ASTM) standards and an in vitro biomechanical study. An axial pullout test was conducted to evaluate the mechanical properties of the new device and the interference screw when implanted in solid rigid polyurethane foam test blocks. The biomechanical test used porcine femora to evaluate the initial fixation strength between these two implants. The maximum pullout force of the interference screw group [722.05 ± 130.49 N (N)] was significantly greater (p

This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing. Mechanical pull-out strength, stiffness and energy-to-failure ratio were recorded for cement-augmented and non-cement-augmented screws. Synthetic bone simulating a human spinal bone with severe osteoporosis was used to measure the maximum extraction torque. The pull-out strength and stiffness-to-failure ratio of cement pre-filled and cement-injected screws were significantly higher than the non-cement-augmented control group. However, the cement pre-filled and cement-injected groups did not differ significantly across these values (p=0.07). The cement pre-filled group had the highest failure pull-out energy, approximately 2.8 times greater than that of the cement-injected (p

Purpose Adjacent segment degeneration or fracture of the vertebral body was commonly reported in rigid fusion. Use of semirigid instruments such as PEEK rod system could be an alternative treatment. However, the biomechanical implications of using PEEK rod systems are not well understood. Purpose of this study was to compare a PEEK rod fixation system to traditional titanium rod fixation via a finite element analysis. Methods A lumbar spine model from L2–L5 vertebral bodies was constructed. A fusion model, created by modifying the intact lumbar model, was used to simulate anterior interbody and posterolateral lumbar fusion. Loading was applied through flexion, extension, lateral bending, torsion. Results The greatest increase in stress was estimated at the upper disc adjacent to the titanium rod with interbody fusion. The lower increase in stress on adjacent segments occurred with PEEK rod fixation without fusion and noninstrumented posterolateral lumbar fusion models. With the same fusion or nonfusion procedures, the stress on discs and facet joints of adjacent segments in the PEEK rod group decreased by 5–25% of that in the titanium rod group for all loading conditions. Conclusion In comparison with rigid fixation, some potential advantages of using PEEK rod systems include a reduced stress on adjacent segment disc and facet joint, and the elastic ability of PEEK rod fixation allows for a greater range of motion, which may reduce the incidence of clinical complications seen with rigid fusion devices.

The swelling properties of buffer material for high level radioactive waste repository in a near-field environment are of particular importance for achieving the low permeability sealing function. In this study, the free swelling behavior of a potential buffer material Zhisin clay is evaluated under simulated groundwater conditions such as immersion in NaCl, CaCl 2 , and Na 2 SO 4 solutions at various concentrations. Experimental results indicate that Zhisin clay, being a Ca-bentonite, exhibits reduced swelling strain in salt solutions. The amount of decrease in swelling strain upon saline water intrusion is affected by both the type and concentration of electrolyte. At the same concentration, the swelling strains in CaCl 2 solution are lower than those in NaCl solution due to the quasi-crystals formed in the presence of calcium ions. Also, the swells in Na 2 SO 4 solution are found to be lower than those in NaCl solution. This is attributed to the precipitation of CaSO 4 , which acts as binding agent and results in aggregation of clay particles.

Initial stability is essential for open reduction internal fixation of intraarticular calcaneal fractures. Geometrical feature of a calcaneal plate is influential to its endurance under physiological load. It is unclear if conventional and pre-contoured anatomical calcaneal plates may exhibit differently in biomechanical perspective. A Sanders' Type II-B intraarticular calcaneal fracture model was reconstructed to evaluate the effectiveness of calcaneal plates using finite element methods. Incremental vertical joint loads up to 450 N were exerted on the subtalar joint to evaluate the stability and safety of the calcaneal plates and bony structure. Results revealed that the anatomical calcaneal plate model had greater average structural stiffness (585.7 N/mm) and lower von Mises stress on the plate (774.5 MPa) compared to those observed in the conventional calcaneal plate model (stiffness: 430.9 N/mm; stress on plate: 867.1 MPa). Although both maximal compressive and maximal tensile stress and strain were lower in the anatomical calcaneal plate group, greater loads on fixation screws were found (average 172.7 MPa compared to 82.18 MPa in the conventional calcaneal plate). It was noted that high magnitude stress concentrations would occur where the bone plate bridges the fracture line on the lateral side of the calcaneus bone. Sufficient fixation strength at the posterolateral calcaneus bone is important for maintaining subtalar joint load after reduction and fixation of a Sanders' Type II-B calcaneal fracture. In addition, geometrical design of a calcaneal plate should worth considering for the mechanical safety in practical usage.

Failure of ultra-high molecular weight polyethylene components after total disc replacements in the lumbar spine has been reported in several retrieval studies, but immediate biomechanical evidence for those mechanical failures remained unclear. Current study aimed to investigate the failure mechanisms of commercial lumbar disc prostheses and to enhance the biomechanical performances of polyethylene components by modifying the articulating surface into a convex geometry. Modified compressive-shearing tests were utilized in finite element analyses for comparing the contact, tensile, and shearing stresses on two commercial disc prostheses and on a concave polyethylene design. The influence of radial clearance on stress distributions and prosthetic stability were considered. The modified compressive-shearing test revealed the possible mechanisms for transverse and radial cracks of polyethylene components, and would be helpful in observing the mechanical risks in the early design stage. Additionally, the concave polyethylene component exhibited lower contact and shearing stresses and more acceptable implant stability when compared with the convex polyethylene design through all radial clearances. Use of a concave polyethylene component in lumbar disc replacements decreased the risk of transverse and radial cracks, and also helped to maintain adequate stability. This design concept should be considered in lumbar disc implant designs in the future.

Backgrounds The post-cam design of contemporary posterior stabilized knee prosthesis can be categorized into flat-on-flat or curve-on-curve contact surfaces. The curve-on-curve design has been demonstrated its advantage of reducing stress concentration when the knee sustained an anteroposterior force with tibial rotation. How the post-cam design affects knee kinematics is still unknown, particularly, to compare the difference between the two design features. Analyzing knee kinematics of posterior stabilized knee prosthesis with various post-cam designs should provide certain instructions to the modification of prosthesis design. Methods A dynamic knee model was utilized to investigate tibiofemoral motion of various post-cam designs during high knee flexion. Two posterior stabilized knee models were constructed with flat-on-flat and curve-on-curve contact surfaces of post-cam. Dynamic data of axial tibial rotation and femoral translation were measured from full-extension to 135°. Findings Internal tibial rotation increased with knee flexion in both designs. Before post-cam engagement, the magnitude of internal tibial rotation was close in the two designs. However, tibial rotation angle decreased beyond femoral cam engaged with tibial post. The rate of reduction of tibial rotation was relatively lower in the curve-on-curve design. From post-cam engagement to extreme flexion, the curve-on-curve design had greater internal tibial rotation. Interpretation Motion constraint was generated by medial impingement of femoral cam on tibial post. It would interfere with the axial motion of the femur relative to the tibia, resulting in decrease of internal tibial rotation. Elimination of rotational constraint should be necessary for achieving better tibial rotation during high knee flexion.

In this paper, we resort to the expectation-maximization (EM) algorithm to tackle the inter-carrier interference (ICI) problem, caused by time-variant multipath channels, for both orthogonal frequency division multiplexing (OFDM) systems and bit-interleaved coded modulation (BICM)/OFDM systems. We first analyze the ICI in frequency domain with a reduced set of parameters, and following this analysis, we derive an EM algorithm for maximum likelihood (ML) data detection. An ML-EM receiver for OFDM systems and a TURBO-EM receiver for BICM/OFDM systems are then developed to reduce computational complexity of the EM algorithm and to exploit temporal diversity, the main idea of which is to integrate the proposed EM algorithm with a groupwise ICI cancellation method. Compared with the ML-EM receiver, the TURBO-EM receiver further employs a soft-output Viterbi algorithm (SOVA) decoder to exchange information with a maximum a posteriori (MAP) EM detector through the turbo principle. Computer simulation demonstrates that the two proposed receivers clearly outperform the conventional one-tap equalizer, and the performance of the TURBO-EM receiver is close to the matched-filter bound even at a normalized maximum Doppler frequency (MDF) up to 0.2.

The fatigue failure of thermoplastic ankle-foot orthoses (AFOs) was observed in clinics. However, there was no standard evaluation for the AFOs to enhance the understanding of how AFOs become more readily acceptable to patients. Therefore, this study aimed to develop an ankle-foot simulator (AFS) as a testing apparatus for AFOs, and performed a pilot test to investigate the failure mechanism of anterior ankle-foot orthosis (AAFO). The accuracy and repeatability of the AFS during cyclic walking, cyclic stepping and cyclic stepping with the AAFO in sagittal plane were measured. The root mean square errors (RMSEs) of cyclic walking of AFS compared to a target gait data were less than 80.52N and 2.55 degrees in the vertical ground reaction force and in the kinematics, respectively. The RMSE of ankle plantarflexion and dorsiflexion of AFS in the cyclic stepping tests were less than 1.25 degrees. The repeatability was assessed by standard deviation, which were less than 9.46N and 0.72 degrees in all testing conditions. A typical failure progression of five AAFOs was observed and graded for four phases under cyclic stepping test. Failure always initiated at the junction of anterior tarsal bar and lateral (or medial) bar of the AAFOs, from which the rest failures were extended. It is suggested that this junction must be reinforced or prevented the stress concentration to elongate the endurance of AAFO.

Headless compression screws (HCSs) are commonly utilized devices for small bone fracture fixation. The Mini-Acutrak 2 and headless reduction (HLR) screws are the newer version types, in which both have fully threaded and variable pitch design. Specifically, the HLR is characterized by two thread runouts to facilitate implantation. With the thread runouts, the holding strength of the screw may be compromised. To the best of our knowledge, no study has examined the pullout force of the global sizes of a HCS. We sought to determine the pullout strength of the HLR and compare the strength of this screw with that of the Mini-Acutrak 2. Synthetic bone blocks with simulated transverse fractures were used to conduct the tests. Four commonly used sizes of the HLR were examined, and one Mini-Acutrak 2 was employed for comparison. Five screws of each size were tested. The pullout force of all screws that were tested in this study ranged from 45.23 to 233.22 N. The results revealed that the pullout force increased as the screw diameter increased. Interestingly, we found that one small screw outperformed the Mini-Acutrak 2, which has a larger diameter. This study provided extensive knowledge regarding the pullout strength of fully threaded HCSs of different sizes. An unexpected finding is that a small screw has higher holding power than a large one because of its increased number of threads. Therefore, we suggest that the thread number should be a critical consideration for the design of size distribution of HCSs.

Calcaneal fracture can lead to long-term disability and have a considerable economic effect. Most calcaneal fractures are intraarticular fractures involving the posterior facet of the subtalar joint. Treating displaced intraarticular calcaneal fractures is complicated because of the lack of an optimal treatment option. Internal fixation typically involves screw-and-plate implants, which can be unfavorable owing to the lack of an anatomic design and the intraoperative bending required for the plate to contour to the irregular surface of the calcaneus. We assessed the outcomes of 30 patients treated using innovative, anatomically designed calcaneal locking plates and the perceived advantages for surgeons. Postoperative computed tomography images of the affected feet were obtained, and the functional performance was recorded. The mean average Böhler angle had increased significantly from 16.8° ± 14.9° to 28.5° ± 9.4° (p .001). The mean average maximal fracture gap and maximal step-off in the posterior facet of the subtalar joint in the coronal computed tomography images also decreased significantly from 2.8 ± 3.7 mm to 0.8 ± 1.3 mm (p .01) and from 3.3 ± 2.8 mm to 0.8 ± 1.2 mm (p .001), respectively. The mean average American Orthopaedic Foot and Ankle Ankle-Hindfoot scale score was 93.9 ± 7.1 at the final follow-up visit. In addition, the surgical time was reduced because bending the plate was not required and the quality of reduction could be assessed easily by examining the gap between the cortex and the plate. The results were promising, revealing that the anatomic locking plate can be used effectively in the treatment of displaced intraarticular calcaneal fractures using simple reduction techniques with a potentially shortened operating time.

Spinal interbody fusion is the most common surgery for treatment of disk degeneration, but the increased stress on adjacent level has been noted. Disk replacement has become an alternative strategy for dealing with problem of disk degeneration. Compressibility of an intact intervertebral disk is contributive to protect spinal structure, but certain mechanism has seldom been preserved in most of the commercial products of ball-and-socket-styled artificial disks. A novel compressible artificial disk design for cervical spine has been developed and compared the biomechanical behaviors with intact and incompressible models by finite element method. Physiological loadings have been applied for evaluating the biomechanical performances in different implant designs. Compressible mechanism represented a similar kinematic behavior to intact cervical spine model. Greater mobility and larger facet joint contact force were observed in incompressible disk model. Biomechanical performances of cervical artificial disk with compressible mechanism may be better reproduced to those of intact cervical spine under physiological loadings. With adequate assigned structural stiffness of the compressible mechanism in the artificial disk, the concept is worth considering for further cervical artificial disk designs.

The inverse kinematics for a robot manipulator with offset wrist is formulated as a minimization problem in this paper to reduce its complexity and accelerate the computation speed. A specific type of robot such as Yaskawa MA1400, which has an offset between the last two axes, is chosen for analysis. Given an initial guess angle of last joint, all the 6 joint angles can be easily found through analytical solution. The output value is compared with the initial guess. An error function with only one variable is then defined and Newton-Raphson method is applied to search for the solution where the error goes to zero. To check the validity of the algorithm, forward kinematics is first computed and the position and orientation of end-effector are then applied in the inverse kinematics to solve the joint angles back. The computation converges within 5 iterations in cases when the angle θ 5 is far away from zero and the accuracy is within 10−10 degree. When θ 5 approaches zero, searching direction is slightly modified to achieve convergence for the algorithm. The number of iterations increases for the same accuracy. The results show that the approach presented in this paper greatly reduces the computation time and is suitable for real time application.

Surgical reconstruction is generally recommended for posterior cruciate ligament (PCL) injuries; however, the use of grafts is still a controversial problem. In this study, a three-dimensional finite element model of the human tibiofemoral joint with articular cartilage layers, menisci, and four main ligaments was constructed to investigate the effects of graft strengths on knee kinematics and in-situ forces of PCL grafts. Nine different graft strengths with stiffness ranging from 0% (PCL rupture) to 200%, in increments of 25%, of an intact PCL's strength were used to simulate the PCL reconstruction. A 100 N posterior tibial drawer load was applied to the knee joint at full extension. Results revealed that the maximum posterior translation of the PCL rupture model (0% stiffness) was 6.77 mm in the medial compartment, which resulted in tibial internal rotation of about 3.01°. After PCL reconstruction with any graft strength, the laxity of the medial tibial compartment was noticeably improved. Tibial translation and rotation were similar to the intact knee after PCL reconstruction with graft strengths ranging from 75% to 125% of an intact PCL. When the graft's strength surpassed 150%, the medial tibia moved forward and external tibial rotation greatly increased. The in-situ forces generated in the PCL grafts ranged from 13.15 N to 75.82 N, depending on the stiffness. In conclusion, the strength of PCL grafts have has a noticeable effect on anterior-posterior translation of the medial tibial compartment and its in-situ force. Similar kinematic response may happen in the models when the PCL graft's strength lies between 75% and 125% of an intact PCL.

Bicondylar tibial plateau fractures are difficult to treat with a high complication rate due to difficulties in achieving stable fixation. External fixation methods such as monolateral external fixator, circular external fixators, or a hybrid between a monolateral and a circular external fixator are considered to be good mechanical methods of stabilising these complex fractures. However, main disadvantages of these traditional external fixators are bulky and cumbersome for the patient during daily activities. Therefore, we developed a simple low-profile external device to overcome these drawbacks. ThisTnovel external device is characterized as arced shape proximally and multi-directional screw insertion trajectory to enhance fixation stability of fracture. This study aimed to investigate the biomechanical performence of the novel device and to compare with commercialized traditional external fixator. Finite element method was employed to carry out all biomechanical analyses. Three CAD models of a normal tibia bone, the simple low-profile external device, and a traditional monolateral external fixator were reconstructed. Bicondylar tibia plateau fracture was simulated according to AO classification (AO/OTA type 41-C1; Schatzker type-V). A 1000N axial compression load was applied to the tibial plateau with fully fixed distal end of the tibia. Maximum von Mises stress on bone, screws, and fixators were calculated. The construct stiffness of both groups were calculated also. The results showed that the maximum von Mises stress on implants was much lower than the yielding strength of the material for both groups. The construct stiffness of the novel device (4992.5 N/mm) was 49.8% higher than the traditional external device (3333.3 N/mm). This study demonstrated that the fixation strength of the novel external device was higher than the traditional monolateral fixator. Clinical evaluation for the novel device is still necessary to further verify its usefulness.

Swelling behavior is an important property in achieving the low-permeability sealing function of buffer material. In this study, free swelling tests were conducted on a potential buffer material under various near field environmental conditions. The potential buffer material used is a locally available clayey material known as Zhisin clay. Experimental results show that Zhisin clay is a temperature-sensitive Ca-bentonite. The maximum swelling strain decreases with increasing hydrothermal temperatures due to lattice contraction. Dry heating of Zhisin clay causes reduction in its cation exchange capacity, which in turn results in decreases of swelling strain. The effects of gamma radiation on the physical and chemical properties of Zhisin clay are found to be similar to those of dry heating. The swell of Zhisin clay under simulated underground geochemistry is affected by both the type of electrolyte and the concentration of solution.

A prac ti cal method for large-scale prep a ra tion of acid-labile aglycones in clud ing protopanaxadiol, protopanaxatriol, cycloastragenol, and jujubogenin from the cor re spond ing glycoside con tain ing frac tion was de vel oped. The key point of this im proved method is to gen er ate and main tain the crit i cal re ac tion con di tions, an hy drous and strongly ba sic, in situ. This ef fort over comes the weak ness of the re ported method for ox i da tive cleav age of glycones and scales up the prep a ra tion of these acid-labile aglycones for fur ther stud ies.

Spinal interbody fusion is the most common surgery for treatment of disc degeneration, but the increased stress and compensatory range of motion at adjacent level have been noted. The dynamic cage design becomes an alternative strategy for dealing with problem of disc degeneration while the bony fusion is eventually required. Concept from a commercial cervical cage product with a ‘Z’-shaped dynamic feature has been evaluated and compared with intact cervical spine and conventional cage design by finite element method. Physiological loadings have been applied for evaluating the effect of cage design on biomechanical performances including adjacent disc stress and segmental range of motion. Results revealed that dynamic characteristic of the dynamic cage design shall effectively reduce the stress and range of motion at the adjacent disc, compared with conventional solid cage design, by providing sufficient mobility by itself. Torsional mobility was constrained due to its geometrical restriction. The dynamic function of cervical cage design may protect the disc adjacent to treat level from over-stressed and excessive mobility in early stage after fusion surgery. Further clinical investigation is required to determine the efficacy of cervical fusion by certain cervical cage with ‘Z’-shaped dynamic feature.

Cannulated pedicle screws are designed for bone cement injection to enhance fixation strength in severely osteoporotic spines. However, the screws commonly fracture during insertion. This study aims to evaluate how different positions/designs of radial holes may affect the pullout and structural strength of cannulated pedicle screws using finite element analysis. Three different screw hole designs were evaluated under torsion and bending conditions. The pullout strength for each screw was determined by axial pullout failure testing. The results showed that when the Von Mises stress reached the yield stress of titanium alloy the screw with four radial holes required a greater torque or bending moment than the nine and twelve hole screws. In the pullout test, the strength and stiffness of each screw with cement augmentation showed no significant differences, but the screw with four radial holes had a greater average pullout strength, which probably resulted from the significantly greater mean maximum lengths of cement augmentation. Superior biomechanical responses, with lower stress around the radial holes and greater pullout strength, represented by cannulated pedicle screw with four radial holes may worth recommending for clinical application.

The primary intent of total knee arthroplasty is the restoration of normal knee kinematics, with ligamentous constraint being a key influential factor. Displacement of the joint line may lead to alterations in ligament attachment sites relative to knee flexion axis and variance of ligamentous constraints on tibiofemoral movement. This study aimed to investigate collaterals strains and tibiofemoral kinematics with different joint line levels.A previously validated knee model was employed to analyse the change in length of the collateral ligaments and tibiofemoral motion during knee flexion. The models shifted the joint line by 3 and 5 mm both proximally and distally from the anatomical level. The data were captured from full extension to flexion 135°.The elevated joint line revealed a relative increase in distance between ligament attachments for both collateral ligaments in comparison with the anatomical model. Also, tibiofemoral movement decreased with an elevation in the joint line. Conversely, lowering the joint line led to a significant decrease in distance between ligament attachments, but greater tibiofemoral motion.Elevation of the joint line would strengthen the capacity of collateral ligaments for knee motion constraint, whereas a distally shifted joint line might have the advantage of improving tibiofemoral movement by slackening the collaterals. It implies that surgeons can appropriately change the joint line position in accordance with patient's requirement or collateral tensions. A lowered joint line level may improve knee kinematics, whereas joint line elevation could be useful to maintain knee stability.V.

Excellent clinical and kinematical performance is commonly reported after medial pivot knee arthroplasty. However, there is conflicting evidence as to whether the posterior cruciate ligament should be retained. This study simulated how the posterior cruciate ligament, post-cam mechanism and medial tibial insert morphology may affect postoperative kinematics. After the computational intact knee model was validated according to the motion of a normal knee, four TKA models were built based on a medial pivot prosthesis; PS type, modified PS type, CR type with PCL retained and CR type with PCL sacrificed. Anteroposterior translation and axial rotation of femoral condyles on the tibia during 0°–135° knee flexion were analyzed. There was no significant difference in kinematics between the intact knee model and reported data for a normal knee. In all TKA models, normal motion was almost fully restored, except for the CR type with PCL sacrificed. Sacrificing the PCL produced paradoxical anterior femoral translation and tibial external rotation during full flexion. Either the posterior cruciate ligament or post-cam mechanism is necessary for medial pivot prostheses to regain normal kinematics after total knee arthroplasty. The morphology of medial tibial insert was also shown to produce a small but noticeable effect on knee kinematics. V.

The computation of kinematics/inverse kinematics in robot manipulators consumes much CPU time and certainly slows down the motion speed of robots. To solve this problem, this paper proposes a hardware implementation of inverse kinematics control IP (Intelligent properties) for robot manipulators based on the FPGA technology. One robot is an articulated type robot manipulator and the other one a SCARA type robot manipulator. In this chapter, the formulations of inverse kinematics for articulated type and SCARA-type robot manipulator are firstly derived. Then, VHSIC Hardware Description Language (VHDL) will be adopted to describe the aforementioned circuit behavior. The design of the VHDL code will apply the finite state machine (FSM) to reduce the hardware resource usage. Under this design, the executing time for computing the inverse kinematics algorithm needs only several micro-seconds. Finally, the simulation results of the inverse kinematic for two type robot manipulators will be compared using the Matlab and Quartus II software in order to demonstrate the effectiveness and correctness of the proposed FPGA-realization of inverse kinematics.

The WNK1 (WNK lysine deficient protein kinase 1) protein is a serine/threonine protein kinase with emerging roles in cancer. WNK1 causes hypertension and hyperkalemia when overexpressed and cardiovascular defects when ablated in mice. In this study, the role of Wnk1 in angiogenesis was explored using the zebrafish model. There are two zebrafish wnk1 isoforms, wnk1a and wnk1b, and both contain all the functional domains found in the human WNK1 protein. Both isoforms are expressed in the embryo at the initiation of angiogenesis and in the posterior cardinal vein (PCV), similar to fms-related tyrosine kinase 4 (flt4). Using morpholino antisense oligonucleotides against wnk1a and wnk1b, we observed that wnk1 morphants have defects in angiogenesis in the head and trunk, similar to flk1/vegfr2 morphants. Furthermore, both wnk1a and wnk1b mRNA can partially rescue the defects in vascular formation caused by flk1/vegfr2 knockdown. Mutation of the kinase domain or the Akt/PI3K phosphorylation site within wnk1 destroys this rescue capability. The rescue experiments provide evidence that wnk1 is a downstream target for Vegfr2 (vascular endothelial growth factor receptor-2) and Akt/PI3K signaling and thereby affects angiogenesis in zebrafish embryos. Furthermore, we found that knockdown of vascular endothelial growth factor receptor-2 (flk1/vegfr2) or vascular endothelial growth factor receptor-3 (flt4/vegfr3) results in a decrease in wnk1a expression, as assessed by in situ hybridization and q-RT-PCR analysis. Thus, the Vegf/Vegfr signaling pathway controls angiogenesis in zebrafish via Akt kinase-mediated phosphorylation and activation of Wnk1 as well as transcriptional regulation of wnk1 expression.

An inverse kinematics IP (Intellectual Property) for six-axis articulated manipulator is investigated in this paper. Firstly, the formulation of the inverse kinematics for six-axis articulated manipulator is derived. Secondly, the computation algorithm and its hardware implementation of some key trigonometric functions are described. Thirdly, the IP design of inverse kinematics is illustrated and VHDL (Very high speed IC Hardware Description Language) is used to describe the overall behavior of the proposed IP. Additionally, VHDL code will apply the parameterized function to increase the code flexibility and the FSM (Finite state machine) is used to reduce the hardware resource usage. Finally, to verify the correctness of the proposed inverse kinematics IP, a co-simulation work is constructed by ModelSim and Simulink. The inverse kinematics hardware IP is run by ModelSim and Simulink models is taken as a test bench that generates stimulus to ModelSim and display the output response. Under this design, computing the inverse kinematics algorithm can be completed within several micro-second.

a b s t r a c t Humeral prostheses commonly use a fin structure as an attachment point for the supraspinatus muscle in total shoulder arthroplasty (TSA), but these fins may cause injury to the muscle during implanta- tion, inadvertently influencing stability. In order to prevent supraspinatus injury, the effect of different humeral prostheses on shoulder joint stability needs to be investigated. A commercially available pros- thesis and two modified humeral prostheses that substituted the fin structure for 2 (2H) or 3 holes (3H) were evaluated using computational models. Glenohumeral abduction was simulated and the superioin- ferior/anterioposterior stability of the shoulder joint after TSA was calculated. The results revealed that the 2H design had better superioinferior stability than the other prostheses, but was still less stable than the intact shoulder. There were no obvious differences in anterioposterior stability, but the motion pat- terns were clearly distinguishable from the intact shoulder model. In conclusion, the 2H design showed better superioinferior stability than the 3H design and the commercial product during glenohumeral joint abduction; the three prostheses show similar results in anterioposterior stability. However, the stability of each tested prosthesis was not comparable to the intact shoulder. Therefore, as a compromise, the 2H design should be considered for TSA because of its superior stability.