bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling of EM propagation in simplified jet turbine structure using helical rays
Authors: Jobs M. , Grudén M. , Rydberg A.
Published: May 2015

To explain the variations in field strength measurements seen when measuring radio‐frequency (RF) propagation in jet turbines, a model based on helical propagating waves is presented. The model uses a simplified model of the jet turbine based on a cylindrical structure and is compared with both electromagnetic (EM) simulations and measured values. Measurements and simulated values show good correspondence and show that a sum of helical propagating waves could be a useful tool to model the expected field variations.
Check node unit for LDPC decoders based on one‐hot data representation of messages
Authors: Boncalo O. , Amaricai A. , Savin V. , Declercq D. , Ghaffari F.
Published: May 2015

A novel check node unit architecture for low‐density parity check (LDPC) decoders, which avoids the usage of carry‐based comparators for the computation of the required first and second minimum values, is presented. It relies on a one‐hot representation of the input messages’ magnitude, obtained by q‐to‐2q decoders. The two minimums are computed using an OR tree and a modified leading zero counter. The proposed architecture is imprecise, as the second minimum is not computed correctly when it is equal to the first one. The implementation results and the analysis of the error correction capability show that the proposed imprecise unit is highly suited for high rate LDPC codes; it presents up to 30% better hardware cost, a higher working frequency, while the loss of the decoding capability is negligible with respect to standard implementations.
Digital predistortion method combining memory polynomial and feed‐forward neural network
Authors: Feng X. , Feuvrie B. , Descamps A.S. , Wang Y.
Published: May 2015

A baseband digital predistortion (DPD) technique based on a feed‐forward neural network (FFNN) is presented. The process of memory polynomial (MP) DPD is time consuming because of the large number of mathematical calculations. The FFNN is adopted to realise the mathematical calculations in MP DPD with direct learning architecture (DLA). The training samples of the FFNN are derived from MP DPD with DLA. It guarantees the accuracy of imitating the MP DPD. Although the training of the FFNN is time consuming, the trained FFNN DPD is less time consuming than MP DPD. This solution is validated based on a power amplifier (PA) ZFL‐2500 driven by a wideband code division multiple access (WCDMA) signal with 3.84 MHz bandwidth. The experimental results show that the FFNN can mimic the behaviour of the MP DPD. The proposed DPD achieves a significant improvement in linearity and is stable.
Compact miniaturised‐element frequency selective surface
Authors: Lin Bao‐qin , Zhou Shan‐hong , Da Xing‐yu , Fang Ying‐wu , Li Yong‐jun , Li Wei
Published: May 2015

A compact miniaturised‐element frequency selective surface (FSS) is proposed for size reduction. The proposed structure can be considered as a common square‐loop slots FSS overlaid with a periodic array of metallic patches mounted on an ultra‐thin dielectric layer. A larger coupling capacitance is brought in each overlap area between the two layers of parallel metallic films. The theoretical analysis and simulation results, together with measured results, demonstrate that a much better compactness characteristic can be realised in the proposed FSS.
Design of compact dual‐passband LTCC filter exploiting stacked QMSIW and EMSIW
Authors: Zhang Xiangjun , Ma Caoyuan , Wang Fei
Published: May 2015

A dual‐passband low‐temperature co‐fired ceramic (LTCC) filter with a stacked quarter‐mode substrate‐integrated waveguide (QMSIW) and an eighth‐mode SIW (EMSIW) on LTCC substrates is presented. By exploiting the QMSIW and EMSIW cavities, the filter has a dual passband with high selectivity and compact size. The experimental filter exhibits two passbands, one is centred at 5.4 GHz with an insertion loss of <1.7 dB, and a 3 dB bandwidth of 13%. The other is centred at 8.3 GHz with an insertion loss of <1.5 dB, and with a bandwidth of 12.9%. The volume of the filter is only 6.5 × 6.5 × 1.2 mm3.
Threshold voltage compensation scheme for RF‐to‐DC converter used in RFID applications
Authors: Chouhan S.S. , Halonen K.
Published: May 2015

A threshold voltage (Vth) compensation scheme is proposed. In this scheme, the bias voltage required to compensate the Vth has been acquired from the input radio‐frequency (RF) signal voltage and the output DC voltage. The proposed rectifier and the self Vth‐cancellation (SVC)‐based rectifier have been designed and fabricated in a standard 0.18 μm CMOS technology. Measurements have been performed for various resistive loads at the ISM 433 MHz frequency. The maximum PCE value achieved by the proposed rectifier is 30% at an input RF power level of −5 dBm whereas the maximum PCE achieved by the SVC is 22% at −9 dBm. These PCEs have been measured at a load resistance of value of 10 kΩ.
Cosine distance features for improved speaker verification
Authors: George K.K. , Kumar C.S. , Ramachandran K.I. , Panda A.
Published: May 2015

Similarities are used with people known already as a means to enhance speaker verification accuracy. Motivated by this, experimental work has been conducted regarding the use of cosine distance (CD) similarity with respect to a set of reference speakers, CD features, with a back‐end support vector machine (CDF‐SVM) classifier for speaker verification. A state‐of‐the‐art i‐vector with CD scoring (i‐CDS) is used as the baseline system for the experiments and for the computation of CD similarity. Experimental results on the telephone speech of the core short2‐short3 conditions of NIST 2008 speaker recognition evaluation (SRE), for female, male and both‐gender trials, show that the proposed CDF‐SVM outperforms the baseline i‐CDS system. The CDF‐SVM achieved an absolute improvement of 1.16% in equal error rate (EER) and 0.38% in minimum DCF over the baseline i‐CDS for female trials. Similar performance improvements were also obtained for the male and all‐gender trials of the SRE. Finally, fusing the CDF‐SVM with i‐CDS gave the best overall performance, an absolute improvement of 4.19% in EER and 1.99% in minimum DCF, over the individual CDF‐SVM system performance for the all‐gender trials. Similar performance improvements were also achieved for male and female trials.
Highly accurate analysis method for LLC dc–dc converters with an improved transformer circuit model
Authors: Ryu Seung‐Hee , Lee Byoung‐Kuk
Published: May 2015

An improved transformer circuit model is proposed for performing a more accurate analysis of LLC dc–dc converters. In the proposed model, the inductances and turns ratio are expressed by a coupling coefficient k. With the help of newly defined parameters for the transformer, voltage gain and switching frequency can be predicted with high accuracy and therefore it becomes possible to design a considerably practical design of the LLC dc–dc converter. The validity of the analysis method using the proposed transformer circuit model is verified by experimental results with a 500 W prototype.
Digital in‐situ biasing technique
Authors: Hsu Chun‐Wei , Kinget Peter R.
Published: May 2015

A highly digital in‐situ biasing solution for analogue interfaces in nanoscale complementary metal‐oxide semiconductor (CMOS) technologies is presented. The digital biasing scheme uses a time‐based successive approximation conversion to provide the desired analogue functions with the voltage/current input and output. The digital biasing circuit obtains benefits from scaled devices with a small dimension and a high Ft, but with no design difficulties by the advanced CMOS process. By taking advantage of ultra‐compact digital logic for control and adaptation, the digital biasing circuit does not suffer from the impact of intra‐die variations since it eliminates the need for shared biasing approaches. A digital common‐mode feedback circuit (CMFB) for a fully differential amplifier was simulated to demonstrate the advantages of the digital in‐situ biasing scheme. The digital CMFB designed in a 65 nm CMOS process provides a desired output common‐mode voltage as a conventional analogue CMFB, but does not need any stability compensation schemes. Compared with the analogue CMFB, the digital CMFB with the digital‐like structure is more robust, has much smaller area, and does not require large passive components.
Minimum required magnetising inductance for multiple‐output flyback DC–DC convertor in CCM
Authors: Kondrath N. , Ayachit A. , Kazimierczuk M.K.
Published: May 2015

The derivation of the equation for the minimum value of magnetising inductance needed for the multiple‐output flyback DC–DC converter to operate in continuous‐conduction mode (CCM) is presented. The equation is derived for two outputs and then generalised for multiple outputs. Two design examples are presented, one for equal output voltages and the other for unequal output voltages. Simulation results are presented in order to verify the derived expressions.
Stability and L2 ‐gain analysis for switched systems with interval time‐varying delay
Authors: Liu Duyu , Liu Xingwen , Xiao Gang
Published: May 2015

This study studies the problem of exponential stability and L2 ‐gain analysis of a class of switched systems with delay varying in an interval. By using a newly constructed Lyapunov–Krasovskii functional and the average dwell‐time scheme, delay‐dependent sufficient conditions are obtained which are expressed as linear matrix inequalities. These conditions provide a solution for finding a switching signal under which exponential stability and normal L2 ‐gain of the switched delay system are guaranteed. Two illustrative examples are given to demonstrate the effectiveness of the proposed results.
Robust passivity, feedback passification and global robust stabilisation for switched non‐linear systems with structural uncertainty
Authors: Pang Hongbo , Zhao Jun
Published: May 2015

This study examines the issues of robust passivity, feedback passification and global stabilisation for a class of switched non‐linear system with structural uncertainty. First, a sufficient condition for such a system to be robust passive is given by the design of a state‐dependent switching law. Second, a state‐dependent switching law and state feedback controllers are designed to render the resulting closed‐loop system robust passive. Finally, a recursive feedback passification design technique is developed to achieve the global stabilisation problem when the subsystems have any uniform vector relative degree. A numerical example is presented to illustrate the effectiveness of the proposed approach.
Colour‐feature dual discriminating correlation analysis for face recognition
Authors: Liu Qian
Published: May 2015

How to effectively utilise the colour image information and extract useful features is the key to colour face recognition. In this study, the authors propose a novel colour face recognition approach named colour‐feature dual discriminating correlation analysis, which incorporates correlation metric into the discriminant analysis technique, and realises colour‐feature discriminating correlation analysis not only within each colour component but also between different components. The public face recognition grand challenge version 2 database is employed as the test data. Experimental results illustrate that the proposed approach outperforms several representative colour face recognition methods.
Analytical tool for the design and optimisation of high‐speed lithium niobate thin‐film Mach–Zehnder modulator
Authors: Ibarra Fuste Jose Antonio
Published: May 2015

An analytical tool for the design and optimisation of high‐speed electro‐optical lithium niobate Mach–Zehnder modulators is developed. This is obtained by merging a closed‐form approach for the radio‐frequency (RF) propagation parameters of the coplanar waveguide forming the electrodes, and closed‐form expressions relating the RF propagation parameters with the modulator bandwidth, driving voltage and length.
Parabolised model of the turbulent wake behind marine turbines
Authors: Fernandez Arturo
Published: May 2015

The extraction of hydrokinetic energy from ocean currents or tides involves the use of marine turbines generating turbulent wakes. The prediction of the wake characteristics is essential because the velocity deficit and increased levels in turbulence intensity dictate the interaction between turbines and any environment impact. A numerical methodology combining the parabolised Navier–Stokes equations with a modified actuator‐disk model is presented. The main innovation of the modified actuator‐disk model is that the flow is considered to be non‐uniform downstream of the turbine. The numerical method is used to reproduce the experiments of Neary et al. (2013) and Mycek et al. (2014). The computational results show that the modification in the actuator‐disk model aids in the reproduction of the experimental measurements. The simulations also show that increased levels in the ambient turbulence intensity cause a faster recovery in the turbulent wake, which agrees with experiments.
Multi‐mode clutter suppression of multiple‐input–multiple‐output over‐the‐horizon radar based on blind source separation
Authors: Dou Daoxiang , Li Mao , He Zishu
Published: May 2015

Spread‐Doppler clutter caused by multi‐mode propagation seriously affects the over‐the‐horizon radar detection performance for slow ships. To solve this problem, the authors propose to suppress multi‐mode clutter using spatial information in the multiple‐input–multiple‐output over‐the‐horizon radar system. Traditional processing algorithms need prior information of the target direction. However, it is often not readily available. In this study, they propose a novel multi‐mode clutter suppression algorithm based on the second‐order blind identification (SOBI) technique. The proposed algorithm does not need prior information of the target direction and can effectively suppress the multi‐mode clutter. Considering that the SOBI algorithm affected by the similarity in sources spectra, they improve the proposed algorithm using the spatial smoothing technique. Simulation results show that, in the single target scene, the improved algorithm can effectively eliminate the spectrum burrs caused by incomplete separation, making separated signals smoother. Signal‐to‐clutter‐noise ratio is greatly improved. The good multi‐mode clutter suppression performance is obtained. In the multi‐mode scenario that double targets with the same radial velocity, that is, sources spectra have similarities, the algorithm based on SOBI cannot separate all targets. Although the improved algorithm can make all targets visible and effectively suppresses the multi‐mode clutter.
Radiographic Analysis of Spinopelvic Sagittal Alignment and Prediction of Lumbar Lordosis in Chinese Asymptomatic Subjects
Authors: Li Wei Shi , Sun Zhuo Ran , Chen Zhong Qiang
Published: May 2015

Introduction

In the past 10 years, the importance of the sagittal shape of human pelvis has been pointed out by the orthopedists. However, most studies were defined in Western and Korean populations. It is unclear whether these characteristics of Chinese spinopelvic sagittal alignment differ from those of western and Korean populations. In addition, the predictive equation of lumbar lordosis remains unclear. This study described normal types of spinopelvic sagittal alignment in Chinese asymptomatic subjects, and investigated a prediction equation of lumbar lordosis from selective spinal and pelvic sagittal parameters.

Material and Methods

This was a prospective radiological analysis using full-spine standing lateral radiographs of Chinese volunteers. A total of 171 volunteers (94 males and 77 females; mean age, 23 years [range, 18–28 years]) participated. Pelvic and spinal parameters were measured according to geometric characteristics. The Pearson correlation test was calculated, regression analysis was running with the lumbar lordosis (predicted variable), and the other spinal and pelvic parameters (predictor variables), to determine the best sets of predictors to include in the model.

Results

Mean pelvic incidence was 44.6 ± 9.5 degrees, significantly less than that reported in Western subjects. The volunteers were classified into four types according to the location of their apex of total lumbar lordosis. As the apex of total lumbar lordosis moved cranially, lordosis tilt decreased, whereas lower lumbar lordosis, pelvic incidence, sacral slope, and the number of vertebral bodies included in the lower lumbar lordosis increased. On the basis of the pelvic incidence, total lumbar lordosis predictive equation was 0.639 PI + 20.593 degrees. Preliminary prediction of lower lumbar lordosis was PI-10 degrees.

Conclusion

The sagittal alignment of Chinese population could be classified into four types, and was different from that of Caucasian. Lower lumbar lordosis comprised most of total lumbar lordosis, the role of pelvic incidence in determining the sagittal curve was mainly through the adjustment of lower lumbar lordosis. Using regression analysis, total lumbar lordosis could be precisely predicted in asymptomatic subjects. To optimally plan surgery for spinal deformity, the prediction of postoperative lower lumbar lordosis curvature was equally important as that of total lumbar lordosis.
Morphometric Features of Posterior Cranial Fossa are Different between Chiari I Malformation with and without Syringomyelia
Authors: Yan Huang , Zhu Zezhang , Liu Zhen , Qian Bang-Ping , Wang Bin , Sun Xu , Yu Yang , Zhu Feng , Qiu Yong
Published: May 2015

Introduction

To investigate whether the posterior cranial fossa (PCF) morphology in Chiari I malformation without syringomyelia (CMI only) is different from that in Chiari I malformation with syringomyelia (CMI-S).

Patients and Methods

A total of 14 patients with CMI and without syringomyelia constituted the CMI-only group, whereas 30 patients with CMI and syringomyelia were assigned to the CMI-S group. Another cohort of 30 age-matched asymptomatic adolescents was enrolled to serve as the control group. Six measurements were evaluated and compared between these three groups from T1-weighted magnetic resonance (MR) imaging, including the length of the clivus (AB), the anteroposterior diameter of the foramen magnum (BC), the length of the supraoccipital (CD), the anteroposterior diameter of the posterior fossa (DA), the posterior fossa height (BE), and the clivus gradient (∠α). The PCF morphology in relation to syrinx severity was also investigated.

Results

Compared with the normal controls, the AB, CD, DA, BE, and ∠α were significantly larger in the CMI-S group. Similar changes in AB, CD, DA, and BE were also demonstrated in the CMI-only group, whereas the clivus gradient (∠α) was found to be relatively normal when compared with the control group. A significantly decreased clivus gradient was observed in the CMI-S groups compared with CMI-only group. In addition, the clivus was significantly flattened in patients with a distended syrinx in comparison to those with a nondistended syrinx.

Conclusion

Small sizes of the posterior fossa were detected both in CMI cases with and without syrinx. The clivus gradient served as the only morphologic difference in the PCF between CMI-S and CMI-only patients and was correlated with the severity of the syrinx, may support the theory that the restricted circulation of cerebrospinal fluid at the anterior paramedial subarachnoid space contributes to the formation of a syrinx.
First Year Experience using an Interdisciplinary Hybrid Operating Theater for Spinal Surgery in a Level 1 Trauma Hospital
Authors: Richter Peter , Yarboro Seth , Kraus Michael , Gebhard Florian
Published: May 2015

Introduction

An interdisciplinary hybrid operating theater was established in June 2012 at the University of Ulm. A floor-based 3D flat panel robotic C-arm (Artis Zeego, Siemens, Germany) is connected to the operating table and the ceiling-based navigation system (BrainLab Curve, BrainLab, Germany). The robotic C-arm is controlled by the surgeon through a control panel mounted on the operating table in the sterile field. The large field of view of the flat panel C-arm allows visualization of the entire lumbar spine or pelvic ring with a single intraoperative 3D scan. This operating room is shared by four different disciplines (orthopedic surgery, neurosurgery, vascular, and cardiac surgery). This hybrid setup represents an advanced imaging and navigation system, and is the first of its type.

Material and Methods

We included all orthopedic surgeries performed in the hybrid operating theater during the first year. All the cases were reviewed for postoperative complications.

Results

A total of 92 cases in 91 patients were performed in the first year. Posterior stabilization of the spine was the most common procedure (57.6%) followed by sacroiliac screws (13%). Other procedures included tumor resection of the spine or pelvis, kyphoplasty, and fixation of acetabular and extremity fractures. Overall, 51.1% of the cases used navigation and 46.7% a minimally invasive technique. Complications included four postoperative seroma and two consecutive infections. All seroma and infections occurred in tumor resections. In large tumor resections, two neurological deficits were detected. Another patient developed dysphagia after fixation of an odontoid and atlas fracture.

Conclusion

None of the complications occurred because of the use of the hybrid operating theater instead of a conventional operating theater. The hybrid operating theater combines high quality, large field intraoperative imaging with advanced navigation. This results in a higher surgeon confidence in hardware placement and total tumor resection. The control panel mounted on the operating table enables the surgeon to operate this complex imaging device in the sterile field. The interdisciplinary use of the operating theater optimizes utilization.
Safety and Efficacy of Skipping C7 Instrumentation in Posterior Cervicothoracic Fusion
Authors: Tobin Matthew , Rangwala Shivani , Birk Daniel , Neckrysh Sergey
Published: May 2015

Introduction

Surgical manipulations at C7 level present the most difficulty during a posterior cervicothoracic fusion where instrumentation across the cervicothoracic junction is required. There is increased risk of vascular injury, neurological injury, and possibility of postoperative instability because of the surgical complications at this site. Placement of C7 instrumentation also poses additional difficulty during rod placement. Vertebral artery (when present) and C8 nerve roots are the most important structures susceptible to the surgical injury at C7 level. Our clinical observations suggested that skipping instrumentation at C7 in a multiple level posterior cervicothoracic fusion will result in minimal intraoperative complications, decreased surgical time, while still maintaining fixation, sagittal balance parameters, and successful rates of fusion.

Methods

This was a retrospective chart review of 49 patients (mean age: 62 years; range: 45–87 years) undergoing multilevel posterior cervicothoracic fusion between November 2010 and October 2014. Of the 49 patients, 42 had no screws placed at C7 level and 7 patients had instrumentation done at C7 and served as a control group. Assessment of the safety and efficacy of skipping C7 instrumentation were based on intraoperative complications, operative time, estimated blood loss (EBL), and radiographic evidence of fusion and spine stability.

Results

There were no intraoperative complications though two patients (one skipped and one not skipped) required extended time under anesthesia because of the difficulty in patient positioning and intubation. Skipping C7 resulted in reduced average operative time compared with those patients instrumented at C7 (203 vs. 171 minutes, respectively). In addition, skipping C7 reduced average EBL compared with patients instrumented at C7 (531 vs. 445 mL, respectively). In addition, patients skipped at C7 maintained sagittal balance with fusion rates identical to control patients at follow-up with a very low incidence of pseudarthrosis.

Conclusion

Skipping instrumentation at C7 in a multilevel posterior cervicothoracic fusion demonstrates lower EBL and faster operative times compared with performing instrumentation at the C7 level. In addition, in a postoperative assessment of patients undergoing posterior cervicothoracic fusion identical rates of fusion were achieved. Serious negative outcomes of skipping C7 were not found in this retrospective study. The results of this study point to the clinical benefits of skipping C7 to minimize surgical risk and complications in patients undergoing posterior cervical fusion across the cervicothoracic junction.
Immediate and Late Postoperative Pain Relief after Kyphoplasty using Unilateral Pedicular Access in Acute and Subacute Osteoporotic Dorsal Lumbar Vertebral Fractures
Authors: Feltes Carlos , Feltes Michelle
Published: May 2015

Introduction

Osteoporotic vertebral compression fractures (VCFs) are a significant cause of disability because of the pain in the elderly population. Kyphoplasty has been advocated as a treatment alternative for the successful management of these fractures in terms of immediate pain relief, and also for restoration of the premorbid level of daily activities. In this retrospective study, the authors report their experience in the period of 8 years (2007–2014) with the early and late management of VCFs with kyphoplasty using a unilateral pedicular approach.

Patients and Methods

A retrospective analysis was conducted in 80 patients (59 women and 21 men) whose ages ranged from 55 to 92 years (mean age, 73 years). The interval between onset of symptoms and surgical intervention ranged from 3 to 12 weeks. Overall, 90 levels (67 thoracic and 23 lumbar) were treated using the unilateral pedicular approach in this cohort. Immediate and early postoperative (3-month follow-up visit) visual analog scale (VAS) pain scores, activity levels, and restoration of vertebral body (VB) height were assessed.

Results

The mean preoperative VAS score was 8.4, whereas the immediate and early postoperative scores were 1.7. These findings reflected a resolution of 85 to 100% of preoperative pain. All patients resumed routine activities within hours of the procedure, although improvement in VB height was not accomplished in this cohort. No major complications were encountered in this clinical series.

Conclusion

Kyphoplasty using a unilateral pedicular approach in this cohort proved to be an effective method for the treatment of osteoporotic VCFs, although failure to restore VB height does not seem to interfere with the excellent pain management and good functional outcome provided by this procedure.
Influence of Nonorganic Signs on Patients undergoing Lumbar Fusion for Degenerative Disorders
Authors: Vialle Emiliano , Vialle Luiz Roberto , Oliveira Barbara , Gomez Juan
Published: May 2015

Introduction

Back pain is an important socioeconomic problem, and the results of the surgical management of lumbar degenerative disorders have a wide variation throughout the literature, possibly because of the several factors affecting pain level and perception in this group of patients. This study aims to evaluate the influence of nonorganic signs on the outcomes of lumbar fusion for degenerative pathologies. The secondary aim is to evaluate the capacity of physicians to identify patients at risk for poor results secondary to nonorganic signs. Material and Method: Prospective clinical study, with independent data collection and analysis pre- and postoperatively (6 months). Patient selection included those with indication for lumbar surgery secondary to lumbar degenerative pathology up to three levels, failure of conservative treatment for at least 6 months and capability to understand the questionnaires and the informed consent. Staff physicians evaluated patients subjectively regarding the presence of depressive and/or nonorganic signs; if the physician suspected that the patient had signs of depression or nonorganic signs, the patient would be excluded from the study. Overall, 60 patients were followed with DRAM, Zung, Oswestry disability questionnaire, presence of nonorganic signs, and VAS pre- and postoperatively. Data regarding spine pathology and patient's medical history were also collected.

Results

There were no significant differences regarding pain levels and surgical results between patients with ( n = 26) and without ( n = 30) nonorganic signs. The same happened with high (50% of the patients) and low scores using the DRAM and Zung evaluation of depressive symptoms.

Conclusion

Although results were similar in the subset of patients, this study showed that subjective analysis was not able to correctly identify patients with risk factors for depression, and that the application of specific questionnaires such as the ones in this study help to improve patient selection for lumbar spine procedures.
Trends in Operative and Conservative Treatments for Lumbar Disc Herniation and Radiculopathy
Authors: Fu Changfeng , Buser Zorica , Wang Justin , Smith Lance , Cohen Jeremiah , Wang Jeffrey
Published: May 2015

Introduction

Lumbar disc herniation is one of the major factors leading to lumbar radiculopathy. Both operative and nonoperative treatments have been shown to be effective in treating patients with lumbar herniated disc and radiculopathy. Even though both approaches can provide a rapid improvement, there are potential adverse events and rising costs associated with both, surgical and nonsurgical procedures. The aim of our study was to better understand the procedural trends, cost, and re-operative incidence in patients with lumbar herniated discs and radiculopathy.

Patients and Methods

Patients with lumbar herniated disc and radiculopathy from 2007 to 2010 were identified in the United healthcare database using ICD-9 and CPT codes. Treatment procedure were recorded and classified in the following three groups: surgical group, including discectomy, microdiscectomy, and endoscopic direct visualization discectomy procedures; minimally invasive group, including endoscopic assistance indirect visualization discectomy, intervertebral chemonucleolysis, and disc aspiration; and nonsurgical group, including bed rest, analgesics, nonsteroidal anti-inflammatory drugs, exercise, physical therapy, or epidural steroid injection. Data were collected and analyzed based on the patient age (< 40, 40–65, and > 65 years) and regional distribution (Midwest, Northeast, South, and West).

Results

A total of 162,682 patients were diagnosed with lumbar disc herniation with sciatica. There were 10,183 patients within the surgical group, 235 in the minimally invasive group, and 152,337 patients in nonsurgical group. There was a significant difference in procedure type based on the age and region. In < 40 years of age subgroup, there was an increase in the operation rates, 5.99, 6.15, 6.32, and 6.51%, from 2007 through 2010. The operation rates decreased with age, 6.95% (< 40 years), 5.65% (40–65 years), and 4.28% in > 65 years group. On the other hand, number of nonsurgical procedures increased with age and was 92.57, 93.99, and 95.32%, respectively. Surgical rates were the highest in the West region (7.58%) and the lowest in the Northeast (3.67%). Nonsurgical procedures had the opposite trends with the Northeast (96.18%) having the highest and West (92.31%) the lowest rate.

Conclusion

There was a difference in the operation rate based on the age and region distribution, with the subgroup < 40 years having the highest operation rate and the > 65 years of age subgroup having the lowest operation rate. The West region has the highest and the Northeast region has the lowest operational rate. Within the nonsurgical group, we observed opposite trends. Our next steps include cost analyzes and defining the surgical likelihood of patient having nonoperative procedures.
Efficacy of Topping-Off Surgery in Preventing Adjacent Segment Degenerative Stenosis of the Lumbar Spine: A Radiographical and Clinical Study
Authors: Hai Yong , Chen Xiaolong
Published: May 2015

Introduction

Adjacent segment degeneration or disease (ASD or ASDs) has been one of the most concerned issues after fusion of the lumbar spine. To investigate the radiographical and clinical outcome of adjacent segment degeneration after topping-off (posterior lumbar interbody fusion + above segment interspinous implant) procedure, a retrospective study was conducted.

Materials and Methods

All lumbar spinal stenosis cases from the department of orthopedics of Beijing Chaoyang hospital that received PLIF + above segment Coflex between August 2008 and October 2012 were analyzed retrospectively. Analysis the gender, age, body mass index of all the patients was done. The X-ray films before and after surgery were measured and got some data (total lordosis, the height of disc, range of motion, lordosis, and olithesis). One-year follow-up were examined by MRI, observed the degeneration of intervertebral disc. All data used SPSS 12.0 for analysis.

Results

There were 32 patients in topping-off (males 21 and females 11), including (L4/5 PLIF + L5–S1 Coflex) 12 patients in group 1 and (L3/4 PLIF +  L4/5 Coflex) 20 patients in group 2. Age averaged 61.5 years (range, 30–79 years) and follow-up averaged 24.6 months (range, 14–63 months). The average surgery time was 110 ± 21 minutes. The average blood loss was 401 ± 110 mL. Postoperation the ODI, JOA, and VAS score improved. There was no significant difference in the height of disc of the Coflex segment and above segment between before and after surgery. Segmental lordosis of Coflex and total lordosis were all increased significantly ( t = −1.9 and −2.0, p < 0.05). There was no significant difference in the number of the disc change of Modic grade of end plate ( p > 0.05).

Conclusion

Topping-off surgery is fit for the patients who have serious stenosis of lumbar spinal cord with mild and moderate stenosis of adjacent segment, which can restrict the adjacent segment's range of motion and prevent excessive olisthesis of adjacent segment in both extension and flexion, also can sustain the height of Coflex segment. It shows a good result after short-term follow-up. Topping-off surgery plays an active role in preventing the adjacent segmental degeneration.
Surgery in Pott Disease: Experience of 582 Cases
Authors: Alam Shah , Karim Rezaul , Islam Sieful , Jonayed Sharif Ahmed , Khalid Hasan , Chakraborty Shubhendu , Alam Tashfique
Published: May 2015

Introduction

Tuberculosis of the spine is the most common and dangerous form of TB infection accounting 50 to 60% of osseous tuberculosis. Although uncommon, spinal TB still occurs even in both developed and developing countries. The diagnosis of spinal tuberculosis is difficult and it commonly presents at an advanced stage. Delay in establishing diagnosis and management cause spinal cord compression and spinal deformity. Patients mostly present with lower limb weakness, Gibbus, pain, palpable mass, and kyphotic deformity in long standing cases.

Material and Methods

To evaluate the efficacy and clinical outcome of surgical treatment of spinal tuberculosis treated by different approaches consisting decompression surgery, autogenous bone grafting and anti-TB chemotherapy. Before that a strong evidence-based diagnosis must be established which can be done by clinical features, MT test, and MRI of spine. Because vertebral body collapse from TB may be misdiagnosed as compression fracture. A total of 582 patients who had tuberculosis of the cervical, thoracic, and lumbar spine with moderate-to-severe cord compression were studied. Variable degrees of neurological deficit with deformity were treated at NITOR and BSOH, Dhaka, in the period from January 2003 to July 2014. Anterolateral decompression and autogenous strut bone grafting with simultaneous fixation by screws and rods were done. Posterior decompression, posterior interbody, and posterolateral fusion by bone graft with stabilization by transpedicular screws and rods. Appropriate anti-TB drugs were given to all patients for 18 to 24 months. The postoperative follow-up period was 12 months (range, 3–21 months).

Results

Overall, 427 (73.4%) cases with neurological deficits recovered totally or partially. No neurological improvement had occurred in 69 (11.9%) cases with paraplegia. Overall, 56 (9.6%) cases were lost from follow-up. X-ray showing bony fusion was achieved in all cases for mean of 6 months (range, 4–8 months). There was no recurrence. Seven (5.1%) cases developed bed sore postoperatively. Excellent result was seen in 70% cases, fair in 15%, good in 10%, and poor in 5% cases.

Conclusion

For patients with spinal tuberculosis anterior debridement, auto graft bone fusion, anterior or posterior fixation appears to be effective in arresting disease, correcting kyphotic deformity and maintaining correction until solid spinal fusion.
Long-Term Outcome of Deep Wound Infection following Lumbar Arthrodesis for Degenerative Disc Disease
Authors: Falavigna Asdrubal , Righesso Orlando , Teles Alisson Roberto , da Silva Pedro Guarise , Volquind Daniel , Traynellis Vincent
Published: May 2015

Introduction

Deep wound infections are one of the most common and serious complications of spinal surgery. The impact of such infections on long-term outcomes is not well understood. The purpose of this study was to evaluate the functional status and satisfaction in patients who suffered a deep wound infection after undergoing lumbar arthrodesis for symptomatic degenerative disc disease.

Patients and Methods

The authors conducted a prospective study in 13 patients with a clinical and radiological diagnosis of symptomatic degenerative lumbar stenosis and instability; after undergoing decompression and instrumentation–augmented arthrodesis, the patients suffered a deep wound infection (infection group). A 3:1 (39 patients) matched cohort was selected for comparison (control group). All surgeries were performed during the same period and by a single surgeon. The postoperative infections were all treated in a similar manner and the instrumentation was not removed. Both groups were followed up and assessed with validated following outcome instruments: Numerical Rating Scale of pain, Oswestry Disability Index, 36-Item Short Form Health Survey, Beck Depression Inventory, and Hospital Anxiety and Depression Scale. Patient satisfaction was also determined.

Results

The median follow-up duration was 22 months (range, 6–108 months). The mean patient age was 62 ± 10 years, and 59.6% of the patients were female. There was no significant difference between the groups in pain, functional disability, quality of life, or depression and anxiety. However, 53.8% of the patients with infection were not satisfied with the procedure at the final evaluation, compared with 15.4% of the patients without a deep wound infection ( p = 0.003).

Conclusion

Patients with successfully treated postoperative deep wound infections do not have a difference in functional outcome compared with patients who underwent an identical operation but did not suffer a complicating infection. Patients who suffered an infection were more likely to be unsatisfied with the procedure than patients who did not.
Application of Current Spine Classification Systems to Civilian Gunshot Wounds that were Designed for Blunt Force Trauma
Authors: Neway William , Staggers Rucker , Theiss Steven
Published: May 2015

Introduction

Spine classification systems have been used for years to create a universal language for describing injuries to the spinal column, as well as guiding clinical management. These classification systems were developed for use with blunt force trauma, but it is unknown whether they can be used for injuries to the spine caused by a gunshot wound.

Purpose

This study aims to investigate whether classification systems such as the Thoracolumbar Injury Classification and Severity Score (TLICS) and the Denis Classification can be applied to spinal injuries as a result of gunshot wounds in addition to blunt force trauma.

Patients and Methods

A retrospective analysis of the trauma patient database registry from the University of Alabama at Birmingham was undertaken for gunshot and spine fracture ICD-9 codes. A total of 32 patients had sustained spinal injuries caused by a gunshot wound. Each patient was evaluated for location of spine fracture and vertebral structures involved, neurological involvement, stability, treatment, and follow-up status. We then applied the TLICS and Denis classification system to evaluate ease of application and usefulness.

Results

A total of 32 patients were evaluated and found to have gunshot wounds that resulted in injury to the spinal vertebra, vertebral ligaments, intervertebral disk, or the spinal cord. The location of injuries ranged from C1 to L5 and varied in the type of fracture. Injuries that had neurological involvement correlated with injury to the posterior column (as per the Denis Classification). There was little correlation with the anterior or middle columns with neurological involvement. Of 32 patients, only 1 had received surgical treatment. This patient had a disruption of all three columns, but similarly, there were nine other patients whose injuries involved all three columns, and yet they did not receive surgery.

Conclusion

TLICS was very difficult to apply to gunshot wounds and the Denis system provided no prognostic information despite a relative ease of use. It is our opinion that a new classification system needs to be designed to specifically include the injury patterns seen from a gunshot wound. Also, there was a little evidence that abstaining from a surgical treatment would cause any significant short- or long-term problems for the patient. Involvement of the posterior column correlated with neurological involvement but does not implicate the need for surgery or debridement.
Assessment and Management of Cervical Spine Injury in Head Injury Victims: A Tertiary Care Center Experience
Authors: Jayabalan Suresh
Published: May 2015

Introduction

Cervical spine injury is the common missed finding during the head injury. As the victims of the same will be unconscious in most occasions, clinical evaluation is difficult and we need to rely on investigation as well as clinical examination. It is important to rule out and manage appropriately to attain the proper outcome.

Patients and Methods

Patients with head injury who were less than GCS 8 and clinical evidence of spinal injuries were added in this study at a tertiary trauma care center at South India for past 4 years. Patients were screened with CT C spine along with CT head on initial evaluation. Any evidence of cervical spinal injury in both imaging and/or clinical examination underwent MRI spine. Treatment initiated appropriately. In a series of 524 patients with GCS less than 8 from May 2010 to May 2014, 74 patients underwent MRI spine based on CT C spine and clinical examination pertaining to cervical spine injury. Patients with thoracic and lumbar spinal injuries were excluded from the study. Follow-up made through clinical visits and telephonic enquiry.

Results

A total of 47 patients had evidence of cervical spine injury in the form of contusions, altered signal changes, spinal stable and unstable fractures, and ligamentous injury. All patients received appropriate treatment including spinal fixation and continuous rehabilitation. Overall, 19 patients presented with unstable spinal fracture which needs stabilization. Overall, eight patients had extensive spinal cord contusions or altered signal changes. Overall, 17 patients had disc bulges or ligamentous injuries with cord signal changes. Overall, two patients had epidural hematoma.

Conclusion

Assessment and diagnosing the cervical spine injury is a real challenge in severe head injury victims. Strict protocol and appropriate management are the key to the success for the proper outcome. CT C spine and clinical examination during the initial evaluation help in attaining the goal and in early decision making.
In Vivo Repair of Rat Annulus Fibrosus Defects using High-Density Collagen Gels
Authors: Moriguchi Yu , Borde Brandon , Grunert Peter , Khair Thamina , Hudson Katherine , Bonassar Lawrence , Härtl Roger
Published: May 2015

Introduction

Although a discectomy successfully relieves the neurological symptoms of a herniated intervertebral disc (IVD), it does not treat the underlying degenerative process; the annular defect remains unrepaired. Persistent annular defect is associated with an increased risk of recurrent herniation and progressive degenerative changes to the IVD. It may also be the primary cause of chronic low back pain following discectomy. To date, there is no established method for repairing annular defects in vivo. The presented study aims to determine whether injectable high-density collagen (HDC) gels can reduce further disc herniation and inhibit degenerative changes in a needle-punctured rat-tail model, and whether riboflavin (RF) cross-linking of injected collagen influences the repair process.

Materials and Methods

A total of 31 athymic rats were punctured with an 18-gauge needle in C3/4 of the caudal spine. They were divided into four groups: group 1 punctured and injected with HDC cross-linked with 0.5 mM (n = 6) or 0.75 mM (n = 7) RF; group 2 punctured and injected with noncross-linked collagen (n = 6); group 3 punctured and untreated (n = 8); group 4 punctured and injected with FITC-labeled cross-linked collagen (n = 4). Degenerative changes to punctured discs, NP size, and NP hydration were analyzed using X-ray, MRI), and histology. Functionality of repaired AF tissue was measured by mechanical tests, by comparing the hydraulic permeability of treated discs to that of healthy discs.

Results

After 5 weeks, untreated discs showed signs of terminal degenerative changes on MRI and histological sections ( Fig. 1 ). No NP tissue remained in the disc space. In contrast, discs treated with RF cross-linked collagen gels retained 63% of NP and 80% of disc height at 5 weeks, and showed minimal degenerative changes on histological section. Interestingly, a series of in vivo imaging showed that after 5 weeks, discs treated with cross-linked HDC demonstrated consistent improvement in both volume and hydration over time, while untreated discs and discs treated with noncross-linked HDC, lost volume, and water content. Injected collagen was seen to form a zipper-like adhesion to the host AF and connective tissue after 1 week and by 5 weeks a fibrous cap that persisted until 18 weeks. NP hydration and IVD functionality of treated discs were found to be similar to those of adjacent healthy discs at 18 weeks. [Figure: see text]

Conclusion

Injection of high-density collagen gel cross-linked with RF can repair annular defects, prevent the degenerative cascade, and maintain the functionality of IVDs in a rat-tail spine. Further studies will be performed to confirm the ability of HDC gels to repair annular defects in a large animal model.