Semi-rigid System Research Articles

Clinical case of treatment of septic defect of bone and soft tissues of the lower leg

the clinical case is an example of complex reconstruction of septic defect of the tibia tissues, the main principles of which were the reduction of traumatic interventions, the choice of optimal multistage tactics; adequate medication. The soft tissue defect was closed with a rotational sural flap, and the bone defect was replaced with a distraction regenerate with the subsequent use of a semi-rigid system of fixation Softcast-Skotchkast; the data of the EFI and Karlstrom-Olerud external fixation index scales with regard to the complexity of the case according to NUSS objectively confirm this.

External mechanical loading overrules cell-cell mechanical communication in sprouting angiogenesis during early bone regeneration.

Sprouting angiogenesis plays a key role during bone regeneration. For example, insufficient early revascularization of the injured site can lead to delayed or non-healing. During sprouting, endothelial cells are known to be mechano-sensitive and respond to local mechanical stimuli. Endothelial cells interact and communicate mechanically with their surroundings, such as outer-vascular stromal cells, through cell-induced traction forces. In addition, external physiological loads act at the healing site, resulting in tissue deformations and impacting cellular arrangements. How these two distinct mechanical cues (cell-induced and external) impact angiogenesis and sprout patterning in early bone healing remains however largely unknown. Therefore, the aim of this study was to investigate the relative role of externally applied and cell-induced mechanical signals in driving sprout patterning at the onset of bone healing. To investigate cellular self-organisation in early bone healing, an in silico model accounting for the mechano-regulation of sprouting angiogenesis and stromal cell organization was developed. Computer model predictions were compared to in vivo experiments of a mouse osteotomy model stabilized with a rigid or a semirigid fixation system. We found that the magnitude and orientation of principal strains within the healing region can explain experimentally observed sprout patterning, under both fixation conditions. Furthermore, upon simulating the selective inhibition of either cell-induced or externally applied mechanical cues, external mechanical signals appear to overrule the mechanical communication acting on a cell-cell interaction level. Such findings illustrate the relevance of external mechanical signals over the local cell-mediated mechanical cues and could be used in the design of fracture treatment strategies for bone regeneration.

Molecular Dynamics Study of Structural and Transport Properties of Silver Iodide Using Effective Charges.

The superionic conductor, solid state, and body-centered cubic structure, silver iodide at room temperature, has been studied via molecular dynamics simulations. The calculated results using pairwise Coulomb-Buckingham potential, zero pressure on the sample, a semi-rigid model system of 1000 Ag and 1000 I ions, () as a statistical ensemble, and an effective charge of for the pairs Ag-Ag and I-I, were found to be consistent with experimental data and one study using , different potential, and simulation software. For the pair Ag-I, there is a discrepancy due to the high silver ion diffusion. The calculated value of the diffusion constant of the silver ion is greater than iodide ion. The dynamic transport properties (mean square displacement, velocity autocorrelation function) results indicated typical behavior reported by other authors, using different potentials in their DM simulations for iodine and silver ions.

Novelties in the islands and tunnel project of the Hong Kong–Zhuhai–Macao Bridge

The Islands and Tunnel Project of the Hong Kong–Zhuhai–Macao Bridge is a design–build contract involving the construction of two artificial islands, each with an area of 100000 m2, that are connected by a 6.7-km-long underwater tunnel. The immersed section of the tunnel consists of 33 elements. This paper examines the novel techniques used during the design and construction of this project. To eliminate its environmental impact, deep piles consisting of steel cylinders and auxiliary cells were developed to build the artificial islands. Novel structural solutions the semi-rigid system were also developed to address the challenges of a high surcharge load and unfavorable layers of soft soil. Moreover, a foundation scheme consisting of a composite foundation layer and a combined foundation was developed to control settlement and prevent leakage. The factory method was implemented to prefabricate the 33 tunnel elements, including five plane-curved elements, where the mass of a typical element was 78000 t. Severe sediment-related problems were encountered during the immersion of elements of the tunnel that necessitated special measures as well as the development of a sediment warning and forecasting system. The closure joints were constructed by using a novel method involving deployable elements. The novelties introduced during the construction of this project are geared toward simplicity, which is conducive to green construction and sustainable solutions. The authors also provide suggestions for improvements if this kind of project were to be undertaken again.

Semi-rigid system for immersed tunnel

The Hong Kong–Zhuhai–Macao Bridge has a total length of 55 km. One of the greatest technical challenges is an immersed tunnel section stretching over 5.664 km and consisting of 33 prefabricated units (tunnel elements). The tunnel is buried 22 m below the seabed, and is therefore subjected to a significant overburden pressure (at a level of ∼100 kPa) during its whole service life. Conventional tunnel elements are either monolithic or segmented. Monolithic elements act like rigid beams, whereas segmented elements behave like a flexible chain. Under this high level of overburden pressure, the tunnel is liable to problems such as concrete cracking, joint opening and leaking. A novel solution for the semi-rigid (structural) system was proposed and adopted. The central idea is to use compressive force and frictional force at the vertical faces of the segment joints to improve the integrity of the longitudinal structure of the tunnel elements. This paper reviews the concept, design and in situ post-construction observations of this semi-rigid system.

Study on bearing characteristics of marine subsoil for semi-rigid immersed tunnel

In the project of Hong Kong-Zhuhai-Macau Bridge, the back-silting of natural foundation section is serious, and the tunnel structure is prone to uneven settlement along the longitudinal direction, and the longitudinal depth of the tunnel will be different due to the navigation demand. The traditional flexible joint scheme will cause great deformation of segment joints and reduce the safety reserve of the shear bearing capacity of the joints. Therefore, the Hong Kong-Zhuhai-Macau immersed tunnel has adopted a semi-rigid system design, that is, after the completion of the prestressing construction of segment joints, the prestressing tendons were not be cut off. The pre-stressed reinforcement can not only ensure the opening of segment joints within a certain range, but they are also adapted to the uneven settlement of the seabed. Notably, prestress plays a very important role in the whole immersed tube tunnel. Therefore, this paper is focused on a comprehensive study of the prestress applied in the semi-rigid scheme. A 1:100 small scale model test of the E13 element in the natural foundation of the immersed tube tunnel is taken as an example. Through the study of two factors, the degree of prestress tension and the size of back silting, the settlement characteristics and the distribution of compressive stresses of marine subsoil on the immersed tunnel are analyzed. The results of the model test showed that the increase in the degree of prestress tension is advantageous to management of the stress and uneven settlement of the joints. Through a comparison of the results of different prestress tension values, the rationality behind the selection of semi-rigid tunnel as a practical engineering scheme is demonstrated. This research lays a foundation for further study on the selection and optimal design of immersed tube tunnels, and the results provide a references point for similar immersed tunnel projects.

Targeting the Rat's Small Bowel: Long-Term Infusion into the Superior Mesenteric Artery.

The superior mesenteric artery can be cannulated in humans through minimally invasive radiological catheterization of the femoral or axillary artery. SMA cannulation is more difficult in rats due to small anatomical dimensions. The aim of the study is to describe a surgical technique for cannulation of the SMA in rats to perform long-term infusion of drugs into the SMA vascular bed in unrestricted animals, which will result in a high rate of catheter patency after the post surgical recovery for 24 hours. To avoid the risk of SMA thrombosis or bleeding from direct access, a proximal branch of the SMA is isolated, ligated distally and cannulated with a 0.25 mm polyurethane capillary tube whose tip is advanced close to the origin of the SMA from the aorta. The cannula is then tunnelled subcutaneously to the back of the animal's neck and through the skin via an artificial valve. The external portion of the cannula is inserted in a semi-rigid support system and connected to the continuous infusion pump outside the cage where the rat is free to move. Correct positioning of the cannula was demonstrated by post-surgical angiography and autopsy findings. Catheter patency after 24 hours of saline infusion into the SMA region was assured in most rats by the total discharge of the pump and recognition of a functional cannula for blood sampling or saline infusion.

Biomechanical Investigation Between Rigid and Semirigid Posterolateral Fixation During Daily Activities: Geometrically Parametric Poroelastic Finite Element Analyses.

While spinal fusion using rigid rods remains the gold standard treatment modality for various lumbar degenerative conditions, its adverse effects, including accelerated adjacent segment disease (ASD), are well known. In order to better understand the performance of semirigid constructs using polyetheretherketone (PEEK) in fixation surgeries, the objective of this study was to analyze the biomechanical performance of PEEK versus Ti rods using a geometrically patient-specific poroelastic finite element (FE) analyses. Ten subject-specific preoperative models were developed, and the validity of the models was evaluated with previous studies. Furthermore, FE models of those lumbar spines were regenerated based on postoperation images for posterolateral fixation at the L4–L5 level. Biomechanical responses for instrumented and adjacent intervertebral discs (IVDs) were analyzed and compared subjected to static and cyclic loading. The preoperative model results were well comparable with previous FE studies. The PEEK construct demonstrated a slightly increased range of motion (ROM) at the instrumented level, but decreased ROM at adjacent levels, as compared with the Ti. However, no significant changes were detected during axial rotation. During cyclic loading, disc height loss, fluid loss, axial stress, and collagen fiber strain in the adjacent IVDs were higher for the Ti construct when compared with the intact and PEEK models. Increased ROM, experienced stress in AF, and fiber strain at adjacent levels were observed for the Ti rod group compared with the intact and PEEK rod group, which can indicate the risk of ASD for rigid fixation. Similar to the aforementioned pattern, disc height loss and fluid loss were significantly higher at adjacent levels in the Ti rod group after cycling loading which alter the fluid–solid interaction of the adjacent IVDs. This phenomenon debilitates the damping quality, which results in disc disability in absorbing stress. Such finding may suggest the advantage of using a semirigid fixation system to decrease the chance of ASD.

THE SEMI-RIGID INDIVIDUAL FUNCTIONAL BANDAGES AS A FINAL STAGE IN THE TREATMENT OF THE TIBIAL BONE NONUNIONS AFTER TREATMENT WITH RING FIXATORS

Summary. The tibia non-unions after fractures require complex and durable treatment. One of the most common methods of variable osteosynthesis is the Ilizarov method. The long period of treatment causes the development of bone reaction to the immersion parts of the ring fixation (RF), osteoporosis, and as a result - reduction of the rigidity of the "fixator - bone fragments" system. All this is the basis for the application of the final stage of low-traumatic methods of fragments fixation with external bandages. Objective. The task of the study is to improve the results of tibial bone non-unions treatment after changeable osteosynthesis with ring fixators, based on the application of external individual fixation with semi-rigid bandages at the final stage of treatment. Material and methods. In our study, we had 36 patients with tibial bone non-unions under observation which have been treated with changeable osteosynthesis with RF. For the sake of prevention of displacement of the fragments, deformation of the regenerate, treatment of tissues inflammation in the area of pins implantation after disassembly of the Ilizarov device; and for the early rehabilitation of the calf functions - used individual semi-rigid fixation system Scotchcast/Softcast. The system allowed to create atraumatic conditions for regeneration and consolidation, full loading of the limb, its full usage during walking. The combination of rigidity (Sotshstast) and elasticity (Softstast) in the system of semi-rigid fixation with polymeric materials allowed the circular rounds of Softstast to change the shape of the bandage. In point of this, we were offered a method of pneumatic massage, which provided massage during the immobilization stage of treatment. Conducting kinesiotherapy and massage therapy was supplemented by medicament therapy. Results. The assessment also took into consideration the structure of non-unions with the Non-Union Scoring System - NUSS scale. The distribution of patients according to the total NUSS score indicated a very complex contingent of victims with a low probability of obtaining good results. Patients who needed standard methods of treatment, with a high probability of obtaining a positive result, were not observed; all required specialized treatments with the likelihood of achieving a positive result. In 20 cases, there was a need for complex specialized medical care with a possible positive result. 2 observation cases showed that even complex specialized medical care did not guarantee a positive result. Evaluation of the results of treatment of the victims with tibial bone non-unions after fractures were performed using the Modified Functional Evaluation System by Karlstrom-Olerud. Good results were obtained in 20 patients (30.45 ± 0.88 points, p <0.001) - 55.6%. Satisfactory results were observed in 7 patients (28.0 ± 0.125 points, p <0.001) - 19.4%. Moderate function impairment (4 patients - 13.9%) was 22.0 ± 1.323 p p <0.001. Poor, unsatisfactory results were observed in 1 case (2.8%); excellent functional status - 3 (8.3%). Conclusions. The usage of semi-rigid fixation systems at the final stage of treatment of tibial non-unions after osteosynthesis with ring fixators should be considered reasonable and safe. The results of the treatment of 36 patients with tibial bone non-unions with preliminary fixation by ring fixators according to the Ilizarov method, using semi-rigid fixation systems at the final stage of treatment -indicate high efficiency.

Behavior of HCR semi-rigid joints under complex loads and its effect on stability of steel cooling towers

A single-layer reticulated steel (SRS) cooling tower consists of members and joints. Joint stiffness is an important component of SRS cooling towers, as it significantly influences the overall behavior of the structure. A new semi-rigid joint system consisting of H-shaped and C-shaped rolled steel, known as an HCR joint, has been developed for application in SRS cooling towers. In this study, a finite element (FE) model of an HCR joint under bending conditions is established and verified by joint tests. Then, HCR joints subjected to different loading combinations, including bending and shear forces, bending and certain axial forces, and eccentric forces, are numerically analyzed. The bending moment-rotation (M-Φ) curves and change rules for the stiffness and ultimate bending capacity are obtained. Next, the stability of SRS cooling towers with semi-rigid HCR joints is analyzed based on the M-Φ curves of the HCR joints under various eccentric forces. Two FE models of the structures are established. In FE Model-1, the stiffness of the HCR joints under a bending load is used for all of the joints in the structure. In FE Model-2, the stiffness of the HCR joints under different eccentric forces are used based on the different ratios of bending force to axial force in the joints at different locations in the structure. During the analysis, the structural height, grid size, and joint stiffness are considered, and the effect of the parameters on the critical load and buckling mode of the structure is determined.

Biomechanical investigation of the effect of pedicle-based hybrid stabilization constructs: A finite element study.

Hybrid stabilization is widely performed for the surgical treatment of degenerative disk diseases. Pedicle-based hybrid stabilization intends to reduce fusion-associated drawbacks of adjacent segment degeneration, construct failure, and pseudoarthrosis. Recently, many types of pedicle-based hybrid stabilization systems have been developed and optimized, using polymeric devices as an adjunct for lumbar fusion procedures. Therefore, the purpose of this study was to evaluate the effect of new pedicle-based hybrid stabilization on bending stiffness and center of rotation at operated and adjacent levels in comparison with established semirigid and rigid devices in lumbar fusion procedures. A validated three-dimensional finite element model of the L3-S1 segments was modified to simulate postoperative changes during combined loading (moment of 7.5 N m + follower load of 400 N). Two models instrumented with pedicle-based hybrid stabilization (Dynesys Transition Optima, NFlex), semirigid system (polyetheretherketone), and rigid fixation system (titanium rod (Ti) were compared with those of the healthy and degenerated models. Contact force on the facet joint during extension increased in fusion (40 N) with an increase of bending stiffness in Dynesys and NFlex. The center of rotation shifted in posterior and cranial directions of the fused level. The centers of rotation in the lower lumbar spine is segment dependent and altered with the adopted construct. The bending stiffness was varied from 1.47 N m/° in lateral bending for the healthy model to 5.75 N m/° for the NFlex stabilization, which had the closest center of rotation, compared to the healthy center of rotation. Locations of center of rotation, stress, and strain distribution varied according to construct design and materials used. These data could help understand the biomechanical effects of current pedicle-based hybrid stabilization on the behavior of the lower lumbar spine.

Dual pitch titanium-coated pedicle screws improve initial and early fixation in a polyetheretherketone rod semi-rigid fixation system in sheep.

Background:Reports on the efficacy of modifications to the thread design of pedicle screws are scarce. The aim of the study was to investigate initial and early fixation of pedicle screws with a plasma-sprayed titanium coating and dual pitch in the pedicle region (dual pitch titanium-coated pedicle screw [DPTCPS]) in a polyetheretherketone (PEEK) rod semi-rigid fixation system.Methods:Fifty-four sheep spine specimens and 64 sheep were used to investigate initial (“0-week” controls) and early (post-operative 6 months) fixation, respectively. Sheep were divided into dual pitch pedicle screw (DPPS), standard pitch pedicle screw (SPPS), DPTCPS, and standard pitch titanium-coated pedicle screw (SPTCPS) groups. Specimens/sheep were instrumented with four screws and two rods. Biomechanical evaluations were performed, and histology at the implant-bone interface was investigated.Results:At 0-week, mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS (557.0 ± 25.2 vs. 459.1 ± 19.1 N, t = 3.61, P < 0.05; 622.6 ± 25.2 vs. 459.1 ± 19.1 N, t = 3.43, P < 0.05). On toggle-testing, the DPTCPS was significantly more resistant than the SPPS and SPTCPS (343.4 ± 16.5 vs. 237.5 ± 12.9 N, t = 3.52, P < 0.05; 343.4 ± 16.5 vs. 289.9 ± 12.8 N, t = 3.12, P < 0.05; 124.7 ± 13.5 vs. 41.9 ± 4.3 cycles, t = 2.18, P < 0.05; 124.7 ± 13.5 vs.79.5 ± 11.8 cycles, t = 2.76, P < 0.05). On cyclic loading, maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS (1.8 ± 0.13 vs. 3.76 ± 0.19 mm, t = 2.29, P < 0.05; 1.8 ± 0.13 vs. 2.46 ± 10.20 mm, t = 2.69, P < 0.05). At post-operative 6 months, mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS (908.4 ± 33.6 vs. 646.5 ± 59.4 N, t = 3.34, P < 0.05; 925.9 ± 53.9 vs. 646.5 ± 59.4 N, t = 3.37, P < 0.05). On toggle-testing, the DPTCPS was significantly more resistant than the SPPS and SPTCPS (496.9 ± 17.9 vs. 370.3 ± 16.4 N, t = 2.86, P < 0.05; 496.9 ± 17.9 vs. 414.1 ± 12.8 N, t = 2.74, P < 0.05; 249.1 ± 11.0 vs.149.9 ± 11.1 cycles, t = 2.54, P < 0.05; 249.1 ± 11.0 vs.199.8 ± 7.2 cycles, t = 2.61, P < 0.05). On cyclic loading, maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS (0.96 ± 0.11 vs. 2.39 ± 0.14 mm, t = 2.57, P < 0.05; 0.96 ± 0.11 vs. 1.82 ± 0.12 mm, t = 2.73, P < 0.05). Resistance to toggle testing (370.3 ± 16.4 vs. 414.1 ± 12.8 N, t = 3.29, P < 0.05; 149.9 ± 11.1 vs.199.8 ± 7.2 cycles, t = 2.97, P < 0.05) was significantly lower and maximum displacement in cyclic loading (2.39 ± 0.14 vs.1.82 ± 0.12 mm; t = 3.06, P < 0.05) was significantly higher for the SPTCPS than the DPTCPS. Bone-to-implant contact was significantly increased for the DPTCPS compared to the SPPS (58.3% ± 7.0% vs. 36.5% ± 4.4%, t = 2.74, P < 0.05); there was no inflammatory reaction or degradation of coated particles.Conclusion:DPTCPSs might have stronger initial and early fixation in a PEEK rod semi-rigid fixation system.

Mechanical performance of an improved semi-rigid joint system under bending and axial forces for aluminum single-layer reticulated shells

In this study, the traditional Temcor joint (TR-Temcor) is modified using a central hollow hexagonal prism and some front bolts. The Finite Element Analysis (FEA) model is established and verified by experiments. Then, a parametric analysis is carried out for the improved Temcor joint (IM-Temcor). To obtain the optimal parameters for the modified joint, the key factors, namely: number and location of the front bolts, bolt-hole deviation, pretension force in bolts, thickness of front plate and heat-affected zone caused by the welding work, are considered in the FEA models. The modified joint, with the optimized factors, is analyzed for different static load conditions, considering axial pressure, axial tension, pure bending, bending with axial force, and eccentric axial forces. The overall mechanical behavior of the joint, including the M-Φ curves, initial stiffness, ultimate strength and deformation capacity, as well as the failure modes are identified. The results from the improved joint are compared with corresponding values from of the traditional Temcor joints. The results show that the central hollow hexagonal prism and front bolts significantly improves the stiffness and ultimate strength of the joint, especially when the joint is subjected to pure bending, bending with shear force, axial force, bending with certain axial force and eccentric force.

Two-step relaxation process of colloidal magnetic nanoclusters under pulsed fields

We empirically uncovered a two-step process of a temporal magnetization response under a pulsed field, which was observed by delaying the particle kinetics in a viscous medium. The Brownian alignment of the magnetization easy-axis appeared to occur separately after the rotated moments reached equilibrium, instead of randomly mixed relaxation behavior. The effective cluster moment and anisotropic magnetopotential difference are two key factors for determining each contribution to the steady-state magnetization. This finding adds new insight to the understanding of colloidal magnetic nanoclusters as a semi-rigid dipole system, which has potential applications in biomedical platforms.

Dynamic behaviour and seismic design method of a single-layer reticulated shell with semi-rigid joints

Most of the existing studies on reticulated shells with a semi-rigid joint system have been focused on the mechanical properties under static loads. Taking material and geometric nonlinearities into account, the finite element analysis (FEA) model of a single-layer reticulated shell with semi-rigid joints was established using the software ABAQUS and then validated through comparison with the experimental result. Based on the bending stiffness of a bolt-column (BC) joint obtained through experiments, the dynamic behaviour and a seismic design method for single-layer reticulated shells with semi-rigid joints were investigated in this paper. First, analysis of the free vibration frequency of the single-layer latticed domes with semi-rigid bolt-column (BC) joints was conducted based on several different parameters, including joint stiffness, ratio of rise to span, initial geometric imperfection. Second, the seismic internal force coefficient of the members of the semi-rigidly jointed spherical single-layer reticulated shells of different parameters was studied in detail. Finally, the seismic internal force coefficients for spherical single-layer reticulated shells with semi-rigid joints under a common earthquake were derived.

������������� ���������� ����� ����� ����������� ��������������� ������������ (PJK, PJF). ����������� ������ �������� ���������� � ��� �������

Purpose Our goal is to demonstrate a typical clinical situation that promotes the development of PJF and PJK, as well as a variant of surgical treatment of these complications. Material and methods A case of a fracture of the overlying vertebra above the level of metal fixation of the vertebra and development of proximal junctional kyphosis (PJF and PJK) in a patient operated for degenerative scoliosis of the lumbar spine. Repeated extended stabilization of the spine without cranial level protection resulted in the re-development of this complication. Vertebroplasty of the bodies of two vertebrae cranial from the fixed vertebral motor segment was performed in order to prevent the development of PJF and PJK and a hybrid fixation with a polymeric band on the cranial vertebral motor segment (VMS) was performed. Result Observation for a year confirms a good result of treatment. Conclusion Using vertebroplasty of two vertebrae cranial from the fixed vertebral motor segment with 7-8 ml of bone cement per vertebra prevented the possible development of PJF and PJK in the presented clinical observation and achieved a good clinical outcome. Laminar band fixation of the cranial VMS ensured the transition of the rigid system into a semi-rigid system in its proximal part, which also contributed to prevention of PJF and PJK.

Experimental and numerical research on a new semi-rigid joint for single-layer reticulated structures

Recent challenge for large-span single-layer reticulated structures is the development of a new joint that can provide these structures with adequate stiffness while satisfying various important requirements, such as easy assembly on a construction site. In this paper, a new semi-rigid joint system, which is referred to as the bolt-column (BC) joint, is developed. A series of tests was performed considering different thicknesses of the side plates, pretension forces and diameters of the bolts. A three-dimensional finite element (FE) model of the joint was developed to evaluate the bending stiffness, moment resistance, rotational capacity and failure mode of the joint. A comparison between the computations and experiments highlights the degree of accuracy of the proposed FE models. The moment-rotation curves, which can be introduced in the analysis of the structure, were obtained. The stiffnesses, strengths, rotation behaviours, and failure modes of the joints are carefully compared and discussed. Based on the results, the influence rules of the parameters on the mechanical behaviour of the new joint are obtained, which are helpful for engineers and designers.The results indicate that the application of this type of joint in construction practice is promising. The experimental results are employed to calibrate the finite element models, which are used to conduct a parametric study.

Distortional Influence of Pallet Rack Uprights Subject to Combined Compression and Bending

A pallet rack is a structure in which the beams and uprights are cold-formed steel sections. The beam-upright connections are normally clipped in order to select the beam levels required and for ease of assembly. For this reason, the uprights contain holes and perforations distributed along their length. The complexity of these components, with local, distortional and torsional/flexural buckling behaviour, represents a challenge in structural design. The loads acting on the structure are induced by the weight of pallets to be stored, and transmitted to the uprights by the semi-rigid connection system. Therefore, the uprights are thin-walled singly symmetrical perforated open cross-sections bearing axial load and bending moment simultaneously. The main objective of this paper is to analyse the influence of the bending moment on the load bearing capacity of rack uprights subject to axial load together with bending moment. Bending is induced by means of axial forces eccentrically applied. The influence of bending on the strength capacity of rack uprights is analysed through finite element analysis, where residual stresses and strength enhancement induced during cold forming of sections are also considered. Experimental tests have been performed reproducing the load conditions in order to validate the FEA results. The ultimate load has also been calculated according to the European Standards and compared to experimental results.

Clinical and Radiological Comparison of Semirigid (WavefleX) and Rigid System for the Lumbar Spine.

ObjectiveSpinal fusion operation is an effective treatment in the spinal pathology, but it could change the physiological distribution of load at the instrumented and adjacent segments. This retrospective study compared the radiological and clinical outcomes of patients undergoing lumbar fusion with semirigid rods versus rigid rods system.MethodsUsing transpedicular fixation and posterior lumbar interbody fusion at the level of L4/L5, 20 patients were treated with semirigid rods (WavefleX, SR group), and 20 patients with rigid rods (titanium, RR group). Clinical and radiological outcomes were evaluated, including visual analog score for lower back pain and leg pain, Prolo functional and economic scores, statues of implanted instruments, fusion rate, and complications during 24-month follow-up.ResultsClinical scores were significantly improved until postoperative 24-month follow-up as compared with preoperative scores in both groups (p<0.05), with similar levels of improvement observed at the same time points postoperatively between the 2 groups. Prolo economic scores were significantly improved in SR group compared to RR until 12 months, but this improvement became similar after 18 months. The overall fusion rate was 94.1% until the 24-month follow-up for both groups. No significant complication was observed in both groups.ConclusionThe results of the present study indicate that semirigid rods system with posterior lumbar interbody fusion showed similar clinical and radiological result with rigid rods system until 2 years after instrumentation. The WavefleX rods system, as a semirigid rods with unique characteristics, may be an effective alternative treatment for patients in lumbar fusion.

Serum B-Type Natriuretic Peptide: A Potential Marker for Neoplastic Edema in Brain Tumor Patients?

Compression fractures at adjacent mobile segments have been reported as adjacent segment disease under trauma in several studies. In this study, the occurrence of fractures at the adjacent segment was evaluated experimentally under trauma.Static testing of different fixation systems was performed to show their biomechanical performances. The ovine vertebrae fixed with rigid, dynamic, and semirigid systems were used as test samples. The stiffness values of the systems were obtained by testing the vertebrectomy models under compression bending, lateral bending, and torsion tests. In addition, their effects on the adjacent segments were experimentally evaluated within a drop mechanism. A free-fall drop mechanism was designed and manufactured. Next, 3.5-kg, 5-kg, and 7-kg weights were released from 1 m above the test samples to generate compression fractures. The occurrence of compression fractures was observed with the use of radiograph of test samples, which were obtained before and after the drop test.Dynamic and semirigid systems have advantages compared with rigid systems as the result of their lower stiffness values. Radiographs showed that epiphysis fractures occurred at fixed and adjacent mobile segments, which were fixed with semirigid fixation. In addition, dynamic fixation well preserved the fixed and adjacent mobile segments under trauma.The dynamic system with a polyetheretherketone rod can better preserve both adjacent and fixed segments. However, because of the cantilever beam effect, the semirigid system exhibits a great disadvantage.