Mechanical Behavior of a Multisegmented Tower Anchorage Structure with an Exposed Steel Anchor Box

A tower anchorage structure with an exposed steel anchor box is commonly used for cable-stayed bridges. Many researchers have conducted studies on this structure by considering a single segment. However, in practical engineering, the stress of multisegmented tower anchorage structure is not completely similar to that of single segment, and the forces between segments affect each other. Hence, in this study, the mechanical behavior of a multisegment anchorage structure with an exposed steel anchor box was investigated via finite element analysis. Furthermore, the load transfer path and stress distribution characteristics of the structure were investigated. The results indicate that the horizontal component of the cable force is borne by the side plate of the steel anchor box, the diaphragm, and the side wall of the concrete tower column, while the vertical component is transmitted by the steel anchor box and concrete tower column. Under the action of this cable force, the horizontal component of the cable force borne by the middle segment increases, while the components at the two end segments decrease. The vertical force is greater on the lower tower segments. The stress levels on the side plate and on the diaphragm of the steel anchor box in the middle section are high. Under the cable force load, the frame formed by the end plate and side plate of the steel anchor box expands outward. The end plate is mainly under a tensile load, and the tensile stress level on the lower section exceeds that on the upper section. A high-stress area for the concrete tower is observed in the steel-concrete joint. The stud group of the anchorage structure is subjected to horizontal and vertical shear forces, and no “saddle-shaped” distribution of the stud shear is found. An optimal arrangement method for the stud group was proposed to optimize its mechanical performance.

Study on the Seismic Performance of Prefabricated Single-Segment Steel Jacket Bridge Piers

To study the seismic performance of prefabricated single-segment steel jacket piers connected by grouting sleeves, two scaled symmetrical pier models with different anchorage lengths of the longitudinal reinforcement in the grouting sleeves and a comparative symmetrical cast-in-place (CIP) model were designed. OpenSees finite element models were established and shaking table tests were carried out on the three scaled pier models. The seismic response of each pier was compared and analyzed. Results showed the stiffness of the two prefabricated piers was greater than that of the CIP pier, and other seismic responses were less than those of the CIP piers, The dynamic responses of the two prefabricated bridge models were similar and changing the anchorage length of the reinforcement in the grouting sleeve had little effect on the seismic performance of the prefabricated pier. The simulation results were in good agreement with the experimental results. In the parameter analysis, the counterweight of the pier top had the greatest influence on the seismic performance of the prefabricated pier. The anchorage length of the longitudinal reinforcement in the grouting sleeve could be 6–14 times the diameter of the longitudinal reinforcement. Moreover, the seismic performance was found to be optimal when the thickness of the steel jacket was 5–7 mm.

Clinical effectiveness of posterior-only approach using polyetheretherketone cage combined with single-segment instrumentation for lumbar tuberculosis in children

We sought to investigate the outcomes of posterior-only approach using polyetheretherketone (PEEK) cage combined with single-segment instrumentation (modified-approach) for mono-segment lumbar tuberculosis in children. Between February 2008 and August 2017 in our hospital, 18 children with single-segment lumbar tuberculosis enrolled in this study were treated by modified-approach. Medical records and radiographs were retrospectively analyzed. Mean follow-up time was 54.6 ± 12.1 months. No severe complications were noted to have occurred. Measures indicated there was satisfactory bone fusion for all patients. Mean Cobb angles were significantly decreased from preoperative angle (19.8° ± 13.1°) to those both postoperatively (− 4.9° ± 7.6°) and at final follow-up (− 3.5° ± 7.3°) (both P < 0.05), with a mean angle loss of 1.7° ± 0.9°. The erythrocyte sedimentation rate (ESR) returned to normal levels for all patients within 3 months postoperatively. All patients had significant postoperative improvement in neurological performance. The modified-approach was an effective and feasible treatment option for mono-segment children with lumbar tuberculosis. Such procedures can likely help patients by increasing retainment of lumbar mobility and reducing invasiveness.

Comparison of Pedicle Screw Fixation With or Without Cement Augmentation Combined With Single-segment Isthmic Spondylolisthesis in Osteoporotic Spine

PurposeThis study aims to investigate the necessity of cement-augmented pedicle screw fixation in single-segment isthmic spondylolisthesis with osteoporosis.MethodFifty-nine cases were reviewed retrospectively. Thirty-three cases were in the polymethylmethacrylate-augmented pedicle screw (PMMA-PS) group, and the other 26 cases were in the conventional pedicle screw (CPS) group. Evaluation data included operation time, intraoperative blood loss,hospitalization cost, hospitalization days, rates of fusion, screw loosening, bone cement leakage, visual analog scores (VAS) , Oswestry disability index (ODI) , Lumbar Lordosis（LL）, Pelvic Tilt（PT） and Sacral Slope（SS）. ResultsThe operation time and blood loss in the CPS group decreased significantly compared to the PMMA-PS group (P < 0.05). The average hospitalization cost of the PMMA group was significantly higher than that of the CPS group (P < 0.05). There was no significant difference for the average hospital stay between the 2 groups (P > 0.05). The initial and the last follow-up postoperative VAS and ODI improved significantly in the two groups (P < 0.05). There were no significant differences in VAS and ODI at each time point between the 2 groups (P > 0.05). The last postoperative spine-pelvic parameters were significantly improved compared with preoperation (P < 0.05). In the PMMA-PS group, the fusion rate was 100%. The fusion rate was 96.15% in the CPS group. No significant difference was found between the two groups for the fusion rate (P > 0.05). Nine cases in the PMMA-PS group had bone cement leakage (27.27%). There was not screw loosening in the PMMA-PS group. There were 2 cases of screw loosening in the CPS group. There were no significant differences in screw loosening, postoperative adjacent segment fractures, postoperative infection or postoperative revision between the 2 groups (P > 0.05). ConclusionsThe use of PMMA-PS on a regular basis is not recommended for posterior lumbar interbody fusion for the treatment of single-segment isthmic spondylolisthesis with osteoporosis.

Fault Diagnosis of Permanent Magnet DC Motors Based on Multi-Segment Feature Extraction

For permanent magnet DC motors (PMDCMs), the amplitude of the current signals gradually decreases after the motor starts. Only using the signal features of current in a single segment is not conducive to fault diagnosis for PMDCMs. In this work, multi-segment feature extraction is presented for improving the effect of fault diagnosis of PMDCMs. Additionally, a support vector machine (SVM), a classification and regression tree (CART), and the k-nearest neighbor algorithm (k-NN) are utilized for the construction of fault diagnosis models. The time domain features extracted from several successive segments of current signals make up a feature vector, which is adopted for fault diagnosis of PMDCMs. Experimental results show that multi-segment features have a better diagnostic effect than single-segment features; the average accuracy of fault diagnosis improves by 19.88%. This paper lays the foundation of fault diagnosis for PMDCMs through multi-segment feature extraction and provides a novel method for feature extraction.

Nonstructural Versus Structural Bone Grafting for Interbody Fusion in the Treatment of Lumbar Tuberculosis by a Single Posterior Approach

Background Many types of bone grafting have been reported for successful use in the treatment of lumbar spinal tuberculosis. However, none-structural bone grafting has rarely been studied. This study was aimed to identify the clinical efficacy of nonstructural with structural bone graft for interbody fusion in the surgical treatment of single segment lumbar tuberculosis after one stage posterior debridement.Methods We retrospectively reviewed patients with nonstructural (n=27) and structural (n=22) bone grafting after single-stage posterior debridement and instrumentation for lumbar tuberculosis with at least 24 months of follow-up. Plain radiographs, magnetic resonance imaging, computed tomography scans, and health-related outcomes (e.g., Visual Analog Scale for back pain, the Oswestry Disability Index) were collected and analyzed before and after surgery. Results Both nonstructural and structural bone grafting were associated with significant improvements in the life quality parameters, the laboratory tests, and the Cobb angle of local kyphosis. A slight loss of Cobb angle correction was observed in two groups. Nonstructural bone grafting exhibited the advantages of less operation duration, blood loss and lower bone fusion rate compared with structural bone grafting. There were three complications in the nonstructural bone grafting and four complications in the structural bone grafting group, with no significant difference between two groups.Conclusions In conclusion, nonstructural bone grafting can achieve comparable interbody fusion to structural bone grafting but has less surgical trauma and simpler surgical procedure than structural bone grafting in the treatment of single segment lumbar tuberculosis after one stage posterior debridement and pedicle screws fixation.

Radiographic comparison of lordotic and hyperlordotic implants in L5–S1 anterior lumbar interbody fusion

OBJECTIVE Anterior lumbar interbody fusion (ALIF) used at the lumbosacral junction provides arthrodesis for several indications. The anterior approach allows restoration of lumbar lordosis, an important goal of surgery. With hyperlordotic ALIF implants, several options may be employed to obtain the desired amount of lordosis. In this study, the authors compared the degree of radiographic lordosis achieved with lordotic and hyperlordotic ALIF implants at the L5–S1 segment. METHODS All patients undergoing L5–S1 ALIF from 2 institutions over a 4-year interval were included. Patients < 18 years of age or those with any posterior decompression or osteotomy were excluded. ALIF implants in the lordotic group had 8° or 12° of inherent lordosis, whereas implants in the hyperlordotic group had 20° or 30° of lordosis. Upright standing radiographs were used to determine all radiographic parameters, including lumbar lordosis, segmental lordosis, disc space lordosis, and disc space height. Separate analyses were performed for patients who underwent single-segment fixation at L5–S1 and for the overall cohort. RESULTS A total of 204 patients were included (hyperlordotic group, 93 [45.6%]; lordotic group, 111 [54.4%]). Single-segment ALIF at L5–S1 was performed in 74 patients (hyperlordotic group, 27 [36.5%]; lordotic group, 47 [63.5%]). The overall mean ± SD age was 61.9 ± 12.3 years; 58.3% of patients (n = 119) were women. The mean number of total segments fused was 3.2 ± 2.6. Overall, 66.7% (n = 136) of patients had supine surgery and 33.3% (n = 68) had lateral surgery. Supine positioning was significantly more common in the hyperlordotic group than in the lordotic group (83.9% [78/93] vs 52.3% [58/111], p < 0.001). After adjusting for differences in surgical positioning, the change in lumbar lordosis was significantly greater for hyperlordotic versus lordotic implants (3.6° ± 7.5° vs 0.4° ± 7.5°, p = 0.048) in patients with single-level fusion. For patients receiving hyperlordotic versus lordotic implants, changes were also significantly greater for segmental lordosis (12.4° ± 7.5° vs 8.4° ± 4.9°, p = 0.03) and disc space lordosis (15.3° ± 5.4° vs 9.3° ± 5.8°, p < 0.001) after single-level fusion at L5–S1. The change in disc space height was similar for these 2 groups (p = 0.23). CONCLUSIONS Hyperlordotic implants provided a greater degree of overall lumbar lordosis restoration as well as L5–S1 segmental and disc space lordosis restoration than lordotic implants. The change in disc space height was similar. Differences in lateral and supine positioning did not affect these parameters.

Dynamic Analysis of QTLs on Plant Height with Single Segment Substitution Lines in Rice

Dynamic regulation of QTLs remains mysterious. Single segment substitution lines (SSSLs) and conditional QTL mapping and functional QTL mappings are ideal materials and methods to explore dynamics of QTLs for complex traits. This paper analyzed the dynamics of QTLs on plant height with SSSLs in rice. Five SSSLs were verified with plant height QTLs first. All five QTLs had significant positive effects at one or more developmental stages except QTL1. They interacted each other, with negative effects before 72 d after transplanting and positive effects since then. The five QTLs selectively expressed in specific periods, mainly in the periods from 35 to 42 d and from 49 to 56 d after transplanting. Expressions of epistasis were dispersedly in various periods, negative effects appearing mainly before 35 d. The five QTLs brought the inflexion point ahead of schedule, accelerated growth and degradation, and changed the peak plant height, while their interactions had the opposite effects. The information will be helpful to understand the genetic mechanism for developmental traits.

Comparing the surgical efficacy of a newly designed endoscopic visualized trephine and a conventional trephine for percutaneous endoscopic lumbar discectomy with foraminoplasty for patients with single-segment lumbar disc herniation: A retrospective case -control study

Background Owing to the remarkable evolution of percutaneous endoscopic lumbar discectomy (PELD), the application of spinal endoscopy is shifting from the treatment of soft disk herniation to complex lumbar spinal stenosis. This study aim to compare the surgical efficacy of a newly designed endoscopic visualized trephine and a conventional trephine for PELD with foraminoplasty for patients with single-segment lumbar disc herniation (LDH). Methods A total of 54 patients who were diagnosed with single-segment LDH and received PELD with foraminoplasty at Xuzhou Central Hospital (Xuzhou, China) from January 2016 to June 2020 were included in this case-control study. Data related to the length of incision, amount of intraoperative bleeding, the time required to create the working channel, and intraoperative and postoperative complications were recorded. The Visual Analog Scale (VAS) score was used to assess low back pain and leg pain. Besides, the Oswestry Disability Index (ODI) and Japanese Orthopedic Association (JOA) scores were utilized to evaluate patients’ pain intensity and their sitting and standing abilities. The X-ray fluoroscopy was performed to measure the horizontal and angular displacements of lumbar extension-flexion, and to evaluate the stability of lumbar spine. Results All the patients successfully underwent surgical procedures, except for two patients with injuries in the spinal nerve root of the responsible segment in the conventional trephine group, who were given nutritional supplements for nerve treatment. Besides, there was no significant difference in incision length and operative blood loss between the modern trephine and the conventional trephine groups. However, the time required to create the channel and the duration of fluoroscopy in the modern trephine group were significantly less than those in the conventional trephine group (34.24 ± 5.38 vs. 44.76 ± 6.37 min, P < 0.05). In addition, the VAS, ODI, and JOA scores significantly decreased postoperatively in the two groups. We also found no significant difference in horizontal and angular displacements of lumbar extension-flexion between the two groups pre-operation and at 3- and 12-month post-operation. Conclusion In spite of similar surgical efficacy of the two techniques, the newly designed endoscopic visualized trephine outperformed in terms of operation time and duration of fluoroscopy.