The Design and Simulation of Improved and Multiplex Boost Converter

In a MW-level and high-power wind power system, the level of current and voltage is easy to exceed the capacity of one switch device, so single boost converter has already can't meet the requirements of system. To solve this problem , for 1.2MW direct drive VSCF wind power system this paper designed a improved and multiplex boost converter , the over-voltage protection circuit branch is inserted into the circuit. The system state equation and control strategy are given, and the input current ripple is analyzed. Finally, in the Matlab environment, build the model of direct-drive wind power generation system to verify the feasibility of this circuit. The results show that: the system can run stably, has high efficiency, low ripple and has a good practical value. DOI : http://dx.doi.org/10.11591/telkomnika.v12i4.500

Satellite Rod Fixation around Rod‐fracture Area in Revision Surgery after Three‐column Osteotomy for Severe Kyphoscoliosis

Objective Three‐column osteotomy (3CO) is considered valuable and increasingly utilized in the surgical treatment of severe spine deformity while associated with high implant‐related complications and revision risks. This study aims to evaluate the feasibility and clinical outcomes of satellite rod fixation used around the rod‐fracture area in revision surgery due to rod fracture after 3CO. Methods Twenty‐five patients applying satellite rod fixation in revision surgery from August 2012 to May 2016 were retrospectively reviewed as the SR group. Patients undergoing revision surgery with traditional strategy after 3CO due to rod‐fracture were selected as the TR group. Cobb angle, distance between C7 plumb line and center sacral vertical line (C7PL‐CSVL), global kyphosis (GK) and sagittal vertical axis (SVA) were assessed. Patients were required to fulfill the Scoliosis Research Society‐22 questionnaire (SRS‐22) at pre‐revision and the last follow‐up. The paired t test was used to analyze the difference among pre‐revision, post‐revision and last follow‐up. Results There was no statistical difference in terms of age, gender, body mass index (BMI), fusion level at 1st surgery, and follow‐up period between SR and TR group (all P > 0.05). The operation time (1.5 ± 0.7 h vs 3.2 ± 0.9 h, P  0.05). All patients responded to the SRS‐22 questionnaire and all the domains showed improvements in different levels. As compared to the TR group, the SR group had significantly better pain and management satisfaction scores (all P < 0.05). Additionally, there was no reoccurrence of implant failure during follow‐up and all patients achieved solid bony fusion in SR group. Conclusion Satellite rod fixation around rod‐fracture area is indicated for patients in the requirement of revision surgeries due to rod fracture after 3CO. Compared with traditional revision strategies, revision surgery with satellite rods, if patients are selected adequately, is a simpler procedure with less intraoperative blood loss and shorter operating time

Hemivertebra resection after age three produces the similar results but with less complications compared to earlier surgery: a minimum of 5-year follow-up

Abstract Background The optimal timing for hemivertebra resection remains controversial. Early intervention before 3 years of age seems being able to get better correction with less fusion segments. However, it was also reported that early surgery may be associated with more complications. The purpose of this study is to investigate correction outcomes and complications of delayed hemivertebra resection (between 3 and 5 years of age), in comparison with earlier surgery (before 3 years of age). Methods Patients who had undergone thoracolumbar hemivertebra resection at a single level before 5 years of age and had more than 5 years of follow-up were reviewed. Twenty-four patients had hemivertebra resection surgery below 3 years of age (early surgery, Group E), and 33 patients received surgery between 3 and 5 years of age (delayed surgery, Group D). Radiographs from preoperative, immediately postoperative, and the latest follow-up visits were reviewed to investigate the correction outcomes. Complications were recorded and compared between these two groups. Results The patients of Group E had shorter operation time and less blood loss than those of Group D (P = 0.003 and P = 0.006). Notably, the fusion segments were 2.3 ± 0.7 and 3.1 ± 1.2 in group E and group D (P = 0.005), respectively, indicating group E averagely saved 0.8 motion segments. At the time of surgery, group E had smaller main curve magnitude either in the coronal or in the sagittal plane than group D and experienced similar correction rates of scoliosis (83.3 ± 21.6% vs. 81.2 ± 20.1%, P = 0.707) and kyphosis (65.1 ± 23.8% vs. 71.7 ± 24.9%, P = 0.319). However, group E had relatively higher complication rates than group D and relatively greater correction loss in either coronal or sagittal plane during follow-up. Conclusions Hemivertebra resection resulted in similar correction results in both age groups. However, the rate of complications was lower for Group D than Group E. Thus, for non-kyphotic hemivertebra, surgery may be delayed till 3 to 5 years of age

Abnormal PITX1 gene methylation in adolescent idiopathic scoliosis: a pilot study

Abstract Background The gene of pituitary homeobox 1 (PITX1) has been reported to be down-regulated in adolescent idiopathic scoliosis (AIS), of which the cause has not been well addressed. The abnormal DNA methylation was recently assumed to be an important mechanism for the down-regulated genes expression. However, the association between PITX1 promoter methylation and the etiology of AIS was not clear. Methods The peripheral blood samples of 50 AIS patients and 50 healthy controls were collected and the genomic DNA was extracted. The pyrosequencing assay was used to assess the methylation status of PITX1 promoter and real-time quantitative polymerase chain reaction (PCR) was used to detect the PITX1 gene expression. Comparison analysis was performed using independent t test and Chi-square tests, while correlation analysis were performed with 2-tailed Pearson coefficients. Results The mean methylation level was (3.52 ± 0.96)% in AIS and (1.40 ± 0.81)% in healthy controls (P < 0.0001). The PITX1 gene expression was 0.15 ± 0.08 in AIS and 0.80 ± 0.55 in healthy controls (P < 0.0001). The comparative analysis showed significant difference in age (P = 0.021) and Cobb angle of the main curve (P = 0.0001) between AIS groups with positive and negative methylation. The methylation level of 6 CpG sites in PITX1 promoters was significantly associated with Cobb angle of the main curve (P < 0.001) in AIS. No statistical relationship between PITX1 promoter methylation and gene expression was found in AIS (P = 0.842). Conclusion Significantly higher methylation level and lower PITX1 gene expression are found in AIS patients. PITX1 methylation is associated with Cobb angles of the main curves in AIS. DNA methylation thus plays an important role in the etiology and curve progression in AIS

Halo Gravity Traction Is Associated with Reduced Bone Mineral Density of Patients with Severe Kyphoscoliosis

Background. Halo gravity traction (HGT) is one of the most commonly used perioperative techniques for the treatment of severe kyphoscoliosis. This study was to explore the influence of HGT on the BMD of these patients. Methods. Patients with severe kyphoscoliosis treated by preoperative HGT for at least 2 months were included. Patients’ BMD were assessed by dual-energy X-ray absorptiometry at lumbar spine (LS, L2–L4) and femur neck (FN) of the nondominant side. The weight and duration of traction, as well as baseline characteristics, were recorded. Results. Twenty patients were recruited. The average traction duration was 77.9±13.0 days while the mean traction weight was 39.9%±11.1% of total body weight. Remarkable decrease of BMD was observed at LS of 17 (85%) patients and at FN of 18 (90%) patients. After HGT, 75% of patients were found to have osteoporosis, the incidence of which was significantly higher than that before HGT (35%). The correlation analysis revealed BMD reduction was only significantly correlated with the traction duration. Conclusions. The current study showed that preoperative HGT can have obvious impact on the BMD. The BMD reduction is associated with traction duration, suggesting that long traction duration may bring more bone mineral loss

Clinical Study Halo Gravity Traction Is Associated with Reduced Bone Mineral Density of Patients with Severe Kyphoscoliosis

Background. Halo gravity traction (HGT) is one of the most commonly used perioperative techniques for the treatment of severe kyphoscoliosis. This study was to explore the influence of HGT on the BMD of these patients. Methods. Patients with severe kyphoscoliosis treated by preoperative HGT for at least 2 months were included. Patients&apos; BMD were assessed by dual-energy X-ray absorptiometry at lumbar spine (LS, L2-L4) and femur neck (FN) of the nondominant side. The weight and duration of traction, as well as baseline characteristics, were recorded. Results. Twenty patients were recruited. The average traction duration was 77.9 ± 13.0 days while the mean traction weight was 39.9% ± 11.1% of total body weight. Remarkable decrease of BMD was observed at LS of 17 (85%) patients and at FN of 18 (90%) patients. After HGT, 75% of patients were found to have osteoporosis, the incidence of which was significantly higher than that before HGT (35%). The correlation analysis revealed BMD reduction was only significantly correlated with the traction duration. Conclusions. The current study showed that preoperative HGT can have obvious impact on the BMD. The BMD reduction is associated with traction duration, suggesting that long traction duration may bring more bone mineral loss