Dynamic Stabilization System Research Articles

Development of equipment and technology for precision air-plasma cutting of plate steel

The authors have investigated the structure of cutting seams obtained after cutting steel 09G2S with a new narrow-jet plasma torch of PMVR-5.3 type which has a number of design features in gas dynamic stabilization system (GDS) of plasma arc. To increase the efficiency of GDS in PMVR-5.3 plasma torch, a symmetrical input of plasma-forming gas (PFG) into the flow division system and a gas-dynamic flow stabilizer using two (forming and stabilizing) swirlers with a variable number of swirl channels were used. It is shown that the achieved advantage in GDS efficiency makes it possible to obtain high cutting quality of steel 09G2S with thickness of 40 mm with high productivity and lower energy costs. Analytical methods have proved a high degree of cutting precision of the new torch– a small cut width, no melting and rounding of the upper edge, as well as a grate in the cut lower part and splashes in the cut upper part, almost zero angular deviation, minimum values of the surface microrelief and width of the thermal impact zone. Metallographic analysis and determination of hardness showed the presence of three subzones in the thermal impact zone with significant structural changes in two of them. A number of factors were noted influencing the revealed changes in the structure formation, as well as changes in the elemental composition of the cutting seam surface layer revealed during the X-ray spectral analysis. Attention is drawn to the surface microrelief after plasma cutting, which in all quality indicators is commensurate with machining of the surface after milling and corresponds to the second class of quality in terms of surface cleanliness. It was proved that the use of the new narrow-jet plasma torch allows high-quality cutting of plate steel in thickness range up to 40 mm or more. However, welding of blanks without pre-machining can be carried out with a cutting thickness of no more than 20 mm.

Theoretical Verification of Dynamic Lumbar Interspinous Process Stabilization Device with Memory Alloys

To find an effective method of minimally invasive treatment combining prevention and assistance in the middle zone of conservative treatment and fusion surgery for lumbar degenerative diseases, through the clinical effect observation and the advantage and disadvantage comparison of several commonly used lumbar interspinous dynamic stabilization systems, by analyzing the physiological structure, biomechanics and relevant data of lumbar interspinous processes, based on fully understanding of memory alloy materials, a new dynamic lumbar interspinous fixation device with a memory alloy material has been independently designed and researched, which can not only reconstruct the normal biomechanical characteristics of the lumbar spine and satisfy the normal activities of the human spine, but also avoid damage to the original structure and reduce the incidence of postoperative complications. In addition, the device can be used to optimize the current therapeutic methods. According to our research, the dynamic lumbar interspinous process stabilization device with a memory alloy has theoretically achieved satisfactory results, which can be used to overcome the shortcomings of the existing technology and is superior to the current several dynamic lumbar interspinous process stabilization systems.

Investigation into Cervical Spine Biomechanics Following Single, Multilevel and Hybrid Disc Replacement Surgery with Dynamic Cervical Implant and Fusion: A Finite Element Study.

Cervical fusion has been a standard procedure for treating abnormalities associated with the cervical spine. However, the reliability of anterior cervical discectomy and fusion (ACDF) has become arguable due to its adverse effects on the biomechanics of adjacent segments. One of the drawbacks associated with ACDF is adjacent segment degeneration (ASD), which has served as the base for the development of dynamic stabilization systems (DSS) and total disc replacement (TDR) devices for cervical spine. However, the hybrid surgical technique has also gained popularity recently, but its effect on the biomechanics of cervical spine is not well researched. Thus, the objective of this FE study was to draw a comparison among single-level, bi-level, and hybrid surgery with dynamic cervical implants (DCIs) with traditional fusion. Reductions in the range of motion (ROM) for all the implanted models were observed for all the motions except extension, compared to for the intact model. The maximum increase in the ROM of 42% was observed at segments C5–C6 in the hybrid DCI model. The maximum increase in the adjacent segment’s ROM of 8.7% was observed in the multilevel fusion model. The maximum von Mises stress in the implant was highest for the multilevel DCI model. Our study also showed that the shape of the DCI permitted flexion/extension relatively more compared to lateral bending and axial rotation.

Dynamic Stability of an Electric Monowheel System Using LQG-Based Adaptive Control

This paper presents the simulation and calculation-based aspect of constructing a dynamically stable, self-balancing electric monowheel from first principles. It further goes on to formulate a reference model-based adaptive control structure in order to maintain balance as well as the desired output. First, a mathematical model of the nonlinear system analyzes the vehicle dynamics, followed by an appropriate linearization technique. Suitable parameters for real-time vehicle design are calculated based on specific constraints followed by a proper motor selection. Various control methods are tested and implemented on the state-space model of this system. Initially, classical pole placement control is carried out in MATLAB to observe the responses. The LQR control method is also implemented in MATLAB and Simulink, demonstrating the dynamic stability and self-balancing system property. Subsequently, the system considers an extensive range of rider masses and external disturbances by introducing white noise. The parameter estimation of rider position has been implemented using Kalman Filter estimation, followed by developing an LQG controller for the system, in order to mitigate the disturbances caused by factors such as wind. A comparison between LQR and LQG controllers has been conducted. Finally, a reference model-assisted adaptive control structure has been established for the system to account for sudden parameter changes such as rider mass. A reference model stabilizer has been established for the same purpose, and all results have been obtained by running simulations on MATLAB Simulink.

Treatment of Acute Acromioclavicular Joint Dislocations Type III and Type V by Rockwood Classification Using a Dynamic Stabilization System under Arthroscopic Control with and without Suture of the Ligaments of the Acromioclavicular Joint

Summary. Acute acromioclavicular (AC) joint dislocation is still a challenging task for orthopedic surgeons. Objective: to compare the clinical and radiological results of treatment of patients with acute dislocation of the acromial end of the clavicle who were treated with a dynamic stabilization system with and without suture of acromioclavicular ligaments under arthroscopic control.
 Materials and Methods. A retrospective analysis of the treatment of 44 patients with acute AC joint dislocations type III and type V by Rockwood classification was performed. The patients were divided into 2 groups: group I – 18 patients (40.9%) who underwent stabilization of the dislocation and fixation of the acromial end of the clavicle using a dynamic stabilization system and suture of the ligaments of the acromioclavicular joint under arthroscopic control; group II – 26 patients (59.1%) who underwent stabilization of the dislocation and fixation of the acromial end of the clavicle using a dynamic stabilization system without suture of the ligaments of the acromioclavicular joint under arthroscopic control. There were 40 male (90.9%) and 4 female (9.1%) patients aged 18–58 years (mean age 32.9±10.1 years). The mean time from injury to surgical treatment was 8.3±3.2 days (from 3 to 17 days). Clinical observation was carried out at an average time of 20.1±3.9 months after surgery (from 12 to 28 months). Clinical outcomes were assessed using the Oxford Shoulder scale, the Constant-Murley scale, and the Acromioclavicular Joint Instability Scoring System.
 Results. The mean Oxford Shoulder score at the final follow-up on the injured side was 45.8±1.3 points and 46.2±1.3 points (p=0.422) in groups I and II, respectively. The mean Constant-Murley score at the final follow-up on the injured side was 94.6±2.4 points and 91.7±4.2 points (p=0.0134) in groups I and II, respectively. The mean score on the Acromioclavicular Joint Instability Scoring System at the final follow-up on the injured side was 83.8±7.1 points and 78.1±11.8 points (p=0.075) in groups I and II, respectively. No significant complications were observed in both groups.
 Conclusions. The combination of the arthroscopically assisted technique of reconstruction of the acromioclavicular ligaments using high-strength sutures and fixation of the coracoclavicular ligaments using a dynamic stabilization system provides good long-term clinical results.

Biomechanical Investigation of Lumbar Interbody Fusion Supplemented with Topping-off Instrumentation Using Different Dynamic Stabilization Devices.

A biomechanical comparison study using finite element method. The aim of this study was to investigate effects of different dynamic stabilization devices, including pedicle-based dynamic stabilization system (PBDSS) and interspinous process spacer (ISP), used for topping-off implants on biomechanical responses of human spine after lumbar interbody fusion. Topping-off stabilization technique has been proposed to prevent adjacent segment degeneration following lumbar spine fusion. PBDSS and ISP are the most used dynamic stabilizers for topping-off instrumentation. However, biomechanical differences between them still remain unclear. A validated, normal FE model of human lumbosacral spine was employed. Based on this model, rigid fusion at L4-L5 and moderately disc degeneration at L3-L4 were simulated and used as a comparison baseline. Subsequently, Bioflex and DIAM systems were instrumented at L3-L4 segment to construct PBDSS-based and ISP-based topping-off models. Biomechanical responses of the models to bending moments and vertical vibrational excitation were computed using FE static and random response analyses, respectively. Results from static analysis showed that at L3-L4, the response parameters including annulus stress and range of motion were decreased by 41.6% to 85.2% for PBDSS-based model and by 6.3% to 67% for ISP-based model compared with rigid fusion model. At L2-L3, these parameters were lower in ISP-based model than in PBDSS-based model. Results from random response analysis showed that topping-off instrumentation increased resonant frequency of spine system but decreased dynamic response of annulus stress at L3-L4. PBDSS-based model generated lower dynamic stress than ISP-based model at L3-L4, but the dynamic stress was higher at L2-L3 for PBDSSbased model. Under static and vibration loadings, the PBDSSbased topping-off device (Bioflex) provided a better protection for transition segment, and likelihood of degeneration of supraadjacent segment might be relatively lower when using the ISPbased topping-off device (DIAM).Level of Evidence: 5.

Fatigue wear test comparing vitamin-E-blended crosslinked polyethylene and conventional polyethylene in a Posterior Dynamic Stabilization System of the spine in the laboratory

BackgroundAlthough artificial joints using polyethylene have been developed for various joints, the development of Posterior Dynamic Stabilization system of the spine using polyethylene has proceeded at a much slower pace. There are no studies which compare the abrasion resistance of vitamin-E-blended crosslinked polyethylene (VE) and conventional polyethylene (Virgin) in the spinal region. The purpose of this study was to compare the wear resistance of VE and Virgin in a Posterior Dynamic Stabilization System of the spine. MethodsPosterior Dynamic Stabilization System of the spine uses a polyethylene ball as a sliding surface. A fatigue wear test was repeated up to 1 million cycles at a speed of ±5°, 1 Hz while the rod was being pulled at a load of 50 N. Balls were compared using VE and Virgin in 6 samples each. Ti-6AL-4 V (Ti 64) and Co–Cr–Mo (CoCr) rods were used. Abrasion loss and shape change of the polyethylene balls were compared. ResultsWhen Ti 64 was used as the rod, the average wear amount was −0.01 mg (0.02 mg, 0.01 mg, −0.06 mg) for VE, and 0.23 mg (0.18 mg, 0.13 mg, 0.38 mg) for Virgin. When CoCr was used as the rod, the average wear amount was 0.42 mg (0.71 mg, −0.06 mg, 0.61 mg) for VE, and 0.73 mg (0.72 mg, 0.70 mg, 0.76 mg) for Virgin. Most polyethylene samples showed indentations of 0.1 m or less at the contact point with the set screw. In the combination of Virgin and CoCr, a white patch was observed on the inner side of the polyethylene samples, with a maximum depression of 0.1 mm. ConclusionsA fatigue wear test showed VE to be more efficient in abrasion resistance than Virgin in a Posterior Dynamic Stabilization System of the spine in the laboratory.

Dynamic Stabilization Surgery in Patients with Spinal Stenosis: Long-term Outcomes and the Future.

Retrospective cohort study. The purpose of this study was to analyze the long-term results for patients with lumbar spinal stenosis (LSS) treated with dynamic stabilization (DS) and to consider how we can improve the results. Few studies have reported long-term outcomes of DS surgery for LSS with or without spondylolisthesis. A single-center, single-surgeon consecutive series of LSS patients who underwent DS surgery with at least 5 years of follow-up were retrospectively reviewed. Twenty-seven patients were included in the LSS group and 38 patients in the spondylolisthesis group. Patient characteristics, operative data, radiographic parameters, clinical outcomes, and complications were analyzed at baseline and follow-up. In the LSS group, all radiographic parameters (e.g., disc height, segmental lordosis, segmental range of motion [ROM] at the index level and proximal adjacent level, global lordosis, and global ROM) were maintained well until the last follow-up. In the spondylolisthesis group, global lordosis decreased from 36.5° ± 8.2° to 32.6° ± 6.0° at the last follow-up (P = 0.039), and global ROM decreased from 22.1° ± 6.9° to 18.8° ± 7.1° at the last follow-up (P = 0.012). In both groups, back pain, leg pain, and Oswestry Disability Index scores showed significant and sustained improvements. Screw loosening occurred in three patients (11.1%) in the LSS group and five patients (13.2%) in the spondylolisthesis group. Symptomatic adjacent segment degeneration (ASD) occurred in two patients (7.4%) in the LSS group and three patients (7.9%) in the spondylolisthesis group. Decompression and DS surgery for LSS with or without spondylolisthesis showed favorable long-term surgical outcomes with an acceptable rate of complications and ASD. However, an improved physiological DS system should be developed.Level of Evidence: 4.

Алгоритм динамической стабилизации курсового угла транспортного средства при торможении

As you know, a radical means to prevent skidding of the vehicle (TK) during braking is the use of such integrated automatic active safety systems as anti-lock braking system (ABS), emergency brake booster, traction control system (TRC), electronic brake force distribution system EBD), stability control system (VSC), tire pressure monitoring system (TPWS), electronic control brake system (ECB), electric power steering (EPS), integrated dynamic vehicle control system (VDIM). Also, the stable position of the vehicle when driving on the road is provided by a set of automatic devices (for example dynamic stabilization system, anti-lock and anti-slip systems, etc.). Most of the cases of violation of the stable position of the vehicle on the road are related to the process of its braking. The article considers an alternative approach to stabilizing the position of the vehicle on the road during braking due to another approach to the management of its braking system. The mathematical description and schemes of position of the vehicle in the course of braking are offered. The stability of the position of the vehicle is ensured by braking the rear wheels, or braking one of the rear wheels (internal in relation to the direction of skidding), due to the system of dynamic stabilization of the course angle. Braking of the rear wheels during the initial skidding during braking allows you to stabilize the course angle of the vehicle (with full braking of the rear wheels, the stabilization time is minimal). This significantly reduces the braking efficiency of the vehicle, as only the front wheels are brake. Braking of only one rear wheel allows to provide identical duration of transition process at the highest efficiency of braking of the vehicle. On the example of a conventional vehicle, a comparative analysis of the effectiveness of the methods of dynamic stabilization of the course angle by braking one and two rear wheels.

P63. Current incidence of adjacent segment pathology following lumbar fusion versus motion preserving procedures: a systematic review and meta-analysis of recent projections

P63. Current incidence of adjacent segment pathology following lumbar fusion versus motion preserving procedures: a systematic review and meta-analysis of recent projections

Автоматический синтез непрерывной динамической системы стабилизации на основе искусственных нейронных сетей

The article considers an automated process of synthesising a continuous dynamic stabilization system based on multilayer neural networks. We propose a two-stage solution to the synthesis problem. The first stage involved generating the training dataset. It meant solving the optimum control problem for the dynamic system under consideration multiple times with various initial conditions. We derived optimum control for every initial condition as a function of object states. The second stage involved approximation of the training dataset we generated, which used a multilayer perceptron neural network. This perceptron represents a control unit that covers the entire initial condition space of the control object. The innovative aspect of our work is as follows: we reduced the synthesis problem to the approximation problem, that is, we sought a closed stabilising system by means of approximating the optimum controls obtained while minimising a functional of the integral type. The paper presents a numerical experiment in synthesising a stabilisation system for a track-laying robot. In order to test the stabilisation system synthesised, we consider initial conditions outside the training dataset and show how the system operates when externally perturbed

Design and development of a novel expanding flexible rod device (FRD) for stability in the lumbar spine: A finite-element study.

The aim of this study is to design a novel expanding flexible rod device, for pedicle screw fixation to provide dynamic stability, based on strength and flexibility. Three-dimensional finite-element models of lumbar spine (L1-S) with flexible rod device on L3-L4-L5 levels are developed. The implant material is taken to be Ti-6Al-4V. The models are simulated under different boundary conditions, and the results are compared with intact model. In natural model, total range of motion under 10 Nm moment were found 66.7°, 24.3° and 13.59°, respectively during flexion-extension, lateral bending and axial rotation. The von Mises stress at intact bone was 4 ± 2 MPa and at bone, adjacent to the screw in the implanted bone, was 6 ± 3 MPa. The von Mises stress of disc of intact bone varied from 0.36 to 2.13 MPa while that of the disc between the fixed vertebra of the fixation model reduced by approximately 10% for flexion and 25% for extension compared to intact model. The von Mises stresses of pedicle screw were 120, 135, 110 and 90 MPa during flexion, extension, lateral bending, and axial rotation, respectively. All the stress values were within the safe limit of the material. Using the flexible rod device, flexibility was significantly increased in flexion/extension but not in axial rotation and lateral bending. The results suggest that dynamic stabilization system with respect to fusion is more effective for homogenizing the range of motion of the spine.

The algorithm of diagnosing the development of a skid when driving a two-axle vehicle

Vehicle controllability and stability are the most important operational properties and components of active traffic safety, improving these qualities around the world are given great importance. One of the major challenges when designing algorithms for active safetyvehicle systems is obtaining reliable information about the quantitative vehicle parametersvalues, allowing to judge how these parameters match the specified driver, to predict theemergencysituations incident moment and diagnose these situations (e.g., front or rear axles kidding, the tipping risk, etc.). One of the most common parameters used in practice, characterizing themultiaxial wheeled vehiclesmotion conditions, is thevectordeviation angle of the vehicle center of gravity (CoG) actual velocity from the vector of its theoretical (kinematic) speed. However, determining the actual velocity vector direction of the CoGis associated with great computational difficulties due to the need to build complex predictive Kalmanfilters. A method for determining the two-axle wheeled vehiclesmotion parameters to ensure the dynamic stabilization system operation, allowing reliable and economical diagnosis of skid front or rear axles of a two-axle vehicle.

Mathematical modelling of torque vectoring differentials

Active safety systems which distribute forces between the wheels are an integral part of a modern vehicle. The vast majority of systems are based on the brake systems, and reducing engine power, which certainly reduces the vehicle speed. However, the needs of car owners are constantly changing, there is a need for devices capable of ensuring the distribution of traction between the wheels without having to reduce speed. With this task perfectly cope with the main transmission containing the mechanisms of power distribution (MPD). Power distribution mechanisms have a greater impact on vehicle handling. More often meet term, Torque Vectoring Differential (TVD). They began to be used for the first time since the mid-1990s, and found their application in sports cars, and then in executive cars. The described main gears are an integral part of dynamic stabilization systems. During the vehicle development, these systems are developed and investigated using mathematical modeling methods. Therefore, the paper describes the design, operation principle and kinematic design of the most common. The equations systems describing the dynamics of the links and the mechanism as a whole are also composed. The mathematical modeling of vehicles equipped with TVD is modelled.

The effect of non-fusion dynamic stabilization on biomechanical responses of the implanted lumbar spine during whole-body vibration

Background and objectiveNon-fusion dynamic stabilization surgery is increasingly popular for treating degenerative lumbar disc disease. However, changes in spine biomechanics after application of posterior dynamic fixation devices during whole-body vibration (WBV) remain unclear. The study aimed to examine the effects of non-fusion dynamic stabilization on biomechanical responses of the implanted lumbar spine to vertical WBV. MethodsBy modifying L4–L5 segment of the healthy human L1–sacrum finite element model, single-level disc degeneration, dynamic fixation using the BioFlex system and anterior lumbar interbody fusion (ALIF) with rigid fixation were simulated, respectively. Dynamic responses of stress and strain in the spinal levels for the healthy, degenerated, BioFlex and ALIF models under an axial cyclic loading were investigated and compared. ResultsThe results showed that endplate stress at implant level was lower in the BioFlex model than in the degenerated and ALIF models, but stress of the connecting rod in the BioFlex system was greater than that in the rigid fixation system used in the ALIF. Compared with the healthy model, stress and strain responses in terms of disc bulge, annulus stress and nucleus pressure at adjacent levels were decreased in the degenerated, BioFlex and ALIF models, but no obvious difference was observed in these responses among the three models. ConclusionsThis study may be helpful to understand variations in vibration characteristics of the lumbar spine after application of non-fusion dynamic stabilization system.

Analysis of clinical effect and radiographic outcomes of Isobar TTL system for two-segment lumbar degenerative disease: a retrospective study

BackgroundNonfusion fixation is an effective way to treat lumbar degeneration. In the present study, we analyzed the clinical effects and radiographic outcomes of the Isobar TTL system used to treat two-segment lumbar degenerative disease.MethodForty-one patients diagnosed with two-segment lumbar degenerative disease underwent surgical implantation of the Isobar TTL dynamic stabilization system (n = 20) or a rigid system (n = 21) from January 2013 to June 2017. The mean follow-up time was 23.6 (range 15–37) months. Clinical results were evaluated with the Oswestry Disability Index (ODI), modified Macnab criteria, and the visual analog score (VAS). Radiographic evaluations included the height of the intervertebral space and the range of motion (ROM) of the treated and adjacent segments. The intervertebral disc signal was classified using the modified Pfirrmann grading system and the University of California at Los Angeles (UCLA) system.ResultsThe clinical results, including the ODI and VAS, showed that there was significant improvement in the two groups after implantation and that the difference between the two groups was not significant. In addition, the clinical efficacy indicated by the modified Macnab criteria for the two groups was similar. Radiological outcomes included the height of the intervertebral space, lumbar mobility, and intervertebral disc signal. The height of the intervertebral space of the upper adjacent segment L2/3 in the rigid group was significantly lower than that in the Isobar TTL group at the last follow-up. Furthermore, the number of ROMs of the fixed-segment L3/4 in the Isobar TTL group was significantly less than that before implantation, suggesting that the fixed-segment ROMs in the Isobar TTL group were limited. In addition, the ROM of the upper adjacent segment L2/3 in the last follow-up of the rigid group increased significantly, while that of the Isobar TTL group did not change after implantation. Finally, the incidence of adjacent-segment degeneration (ASD) was significantly greater in the rigid group than in the Isobar TTL group according to the UCLA system.ConclusionThe Isobar TTL system can be clinically effective for treating two-segment lumbar degenerative disease. Compared with rigid fixation, the Isobar TTL system yielded better radiographic outcomes and maintained the mobility of the treated segments with less impact on the proximal adjacent segment.

An evaluation of the host response to an interspinous process device based on a series of spine explants: Device for Intervertebral Assisted Motion (DIAM®)

The objective of this study was to evaluate the host response to an interspinous process device [Device for Intervertebral Assisted Motion (DIAM®)] based on a series of nine spine explants with a mean post-operative explant time of 35 months. Explanted periprosthetic tissues were processed for histology and stained with H&E, Wright-Giemsa stain, and Oil Red O. Brightfield and polarized light microscopy were used to evaluate the host response to the device and the resultant particulate debris. The host response was graded per ASTM F981-04. Quantitative histomorphometry was used to characterize particle size, shape, and area per ASTM F1877-05. The presence or absence of bone resorption was also evaluated when bony tissue samples were provided. Periprosthetic tissues demonstrated a non-specific foreign body response composed of macrophages and foreign body giant cells to the DIAM® device in most of the accessions. The foreign body reaction was not the stated reason for explantation in any of the accessions. Per ASTM F981-04, a "very slight" to "mild" to "moderate" chronic inflammatory response was observed to the biomaterials and particulate, and this varied by tissue sample and accession. Particle sizes were consistent amongst the explant patients with mean particle size on the order of several microns. Osteolysis, signs of toxicity, necrosis, an immune response, and/or device related infection were not observed. Cyclic loading of the spine can cause wear in dynamic stabilization systems such as DIAM®. The fabric nature of the DIAM® device's polyethylene terephthalate jacket coupled with the generation of polymeric particulate debris predisposes the device to a foreign body reaction consisting of macrophages and foreign body giant cells. Although not all patients are aware of symptoms associated with a foreign body reaction to a deeply implanted device, surgeons should be aware of the host response to this device.

Mid-term follow-up efficacy of interspinous dynamic stabilization system for lumbar degenerative diseases

To explore mid-term clinical efficacy and effect on adjacent segment degeneration of Wallis and Coflex interspinous implants for lumbar degenerative diseases. From January 2011 to January 2013, 55 patients with L4, 5 degenerative lumbar spine diseases treated with interspinous devices were retrospectively analyzed, including 31 males and 24 females aged from 25 to 67 years old with an average of 43.3 years old; 21 patients were lumbar spinal stenosis and 34 patients were lumbar disc herniation. All patients were divided into Wallis group (33 cases) and Coflex group (22 cases) according to the interspinous fixation system. Visual analogue scale(VAS) was used to evaluate low back pain and lower limb pain, Japanese Orthopedic Association(JOA) score and Oswestry Disability Index(ODI) score were used to evaluate lumbar function. Surgical segment and adjacent segments, range of motion(ROM), disc height and the Pfirrmann grade of upper the adjacent segments were compared before and after operation. Fifty-five patients were followed up from 48 to 72 months with an average of 60.4 months. VAS score of low back pain and lower limb pain, JOA and ODI score of lumbar at 48 months after operation were improved than before operation between two groups(P<0.01), but there was no statistical difference for group comparisons(P>0.05). ROM, disc height of surgical segments were significantly lower than those before operation between two groups (P<0.05), while ROM of the upper and lower adjacent segments and disc height did not change significantly (P>0.05). There was no significant difference in ROM and disc height for group comparisons(P>0.05). There was no change in Pfirrmann grade of the upper adjacent segment degeneration between two groups(P>0.05). Four patients with primary lumbar disc herniation had a recurrence of 1 to 3 years after operation, including 3 in Wallis group and 1 in Coflex group, with an average age of 35.2 years old. Wallis and Coflex interspinous implants have the similar mid-term efficacy for the treatment of lumbar degenerative diseases, and could delay adjacent segment degeneration, but could not prevent recurrence of disc herniation.

Biomechanical In Vitro Test of a Novel Dynamic Spinal Stabilization System Incorporating Polycarbonate Urethane Material Under Physiological Conditions.

Posterior dynamic stabilization systems (PDSS) were developed to provide stabilization to pathologic or hypermobile spinal segments while maintaining the healthy biomechanics of the spine. Numerous novel dynamic devices incorporate the temperature and moisture dependent material polycarbonate urethane (PCU) due to its mechanical properties and biocompatibility. In this study, standardized pure moment in vitro tests were carried out on human lumbar spines to evaluate the performance of a device containing PCU. An environmental chamber with controlled moisture and temperature was included in the setup to meet the requirements of testing under physiological conditions. Three test conditions were compared: (1) native spine, (2) dynamic instrumentation, and (3) dynamic instrumentation with decompression. The ranges of motion, centers of rotation, and relative pedicle screw motions were evaluated. The device displayed significant stiffening in flexion-extension, lateral bending, and axial rotation load directions. A reduction of the native range of motion diminished the stiffening effect along the spinal column and has the potential to reduce the risk of the onset of degeneration of an adjacent segment. In combination with decompression, the implant decreased the native range of motion for flexion-extension and skew bending, but not for lateral bending and axial rotation. Curve fittings using the sigmoid function were performed to parameterize all load-deflection curves in order to enhance accurate numerical model calibrations and comparisons. The device caused a shift of the center of rotation (COR) in the posterior and caudal direction during flexion-extension loading.

Разработка алгоритма работы системы динамической стабилизации автомобиля с колесной формулой 4х4

Разработка алгоритма работы системы динамической стабилизации автомобиля с колесной формулой 4х4