Segmental Stability Research Articles

P23. Inline axial forces associated with implantation of ALIF interbody devices with integrated supplemental fixation

<h3>BACKGROUND CONTEXT</h3> Anterior lumbar interbody fusion (ALIF) allows for an optimal sized interboy device while providing correction for lumbar lordosis, restoration of disc height and indirect decompression. Spinal interbody devices with integrated fixation through blades, screws or other supplemental anchoring components mitigate the need for supplemental instrumentation, thus reducing OR time and preserving the stability of the functional spinal unit. Unfortunately, interbody devices have failed at the bone implant interface resulting in complications including implant migration and expulsion. Gaining a better understanding of the biomechanics associated with interbody placement may help to prevent these complications in the future. The aim of present study is to determine the magnitude and effect of axial forces during the deployment of an interbody device with supplemental integrated fixation. <h3>PURPOSE</h3> To understand the axial loading imparted to the functional spinal unit during lumbar interbody fusion surgery. <h3>STUDY DESIGN/SETTING</h3> Biomechanical axial load mesaurement in cadaveric functional spinal units during lumbar disc preparation and spinal interbody device implant procedures. <h3>METHODS</h3> Cadaveric functional spinal units, levels L2-L3, L3-L4, L4-L5, and L5-S1, were decorticated to the osteoligamentous structures. Posterior elements were removed to allow for MicroCT imaging of each specimen at a voxel size of 27 micron before and after instrumentation. A custom test fixture was used to apply 50N compressive force to stabilize the specimen and also record inline axial forces associated with the deployment of anchor plates during instrumentation procedures. A Chatillon DFS II force gauge was used to record axial forces during implantation of ENZA 1.0 and ENZA 2.0 interbody devices. Axial forces resulting from implant trialing, device insertion and anchor deployment were recorded. MicroCT scans were repeated to allow for quantification of damage to bony structures as a result of implantation procedures. <h3>RESULTS</h3> L2-L3 and L3-L4 force outputs are similar for both insertion, 218.82 N, 219.89 N, and deployment forces, 34.58 N, 44.88 N respectively. Insertion forces throughout all spinal levels were larger than both deployment and removal forces. Insertion forces were larger in the proximal levels, 218.82 N, 219.89 N, when compared to the distal levels, 178.96 N, 113.76 N. However, deployment force was larger in the distal levels, 99.03 N, 77.76 N, when compared to proximal 34.58 N, 44.88 N. <h3>CONCLUSIONS</h3> As evidence mounts for the cost-effectiveness of standalone cages with integrated supplemental fixation, it is imperative that design requirements of these devices continue to improve. Previous studies have shown that the vertebral endplate is susceptible to fracture under compressive loading, with the weakest area of the vertebrae being the center region. In 2001, Hasegawa et al showed a cylindrical-shaped implant caused endplate fracture between 510N and 1335N and that implant size is inversely related to the force required to cause fracture. Endplate fracture is difficult to detect with standard imaging modalities and leaves the patient vulnerable to implant subsidence and reduces segmental stability as a result of changes in load transfer. Furthermore, endplate failure may be a contributor to low back pain, further reducing the chance of a successful outcome. Our study showed interbody devices with integrated fixation plates could safely be inserted and deployed in the disc space without causing endplate fracture. The implant-endplate interface should be investigated in greater detail to allow for design of standalone interbody devices which do not cause unintended distraction or worse, damage to the vertebrae. <h3>FDA DEVICE/DRUG STATUS</h3> ENZA Lumbar Interbody Fusion Device (Approved for this indication).

Influence of microsurgical decompression on segmental stability of the lumbar spine – One-year results in a prospective, consecutive case series using upright, kinetic-positional MRI

BackgroundStandard procedure in patients with lumbar spinal canal stenosis is decompression to relieve the neural structures. Clinical results generally show superiority compared to nonoperative therapy after an observation period of several years. However, there is still a question of postsurgical segmental stability and correlation to clinical findings. Therefore, the aim of this prospective study was to evaluate the clinical outcome in patients who underwent microsurgical decompression in lumbar spine and particularly to analyze intervertebral movement by use of upright, kinetic-positional magnetic resonance imaging (MRI) over a period of 12 months and then to correlate the clinical and imaging data with each other.MethodsComplete clinical data of 24 consecutive participants with microsurgical decompression of the lumbar spine were obtained by questionnaires including visual analogue scale (VAS) for back and leg, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), Short-Form-36 (SF-36), walking distance and use of analgesics with assessment preoperatively and after 6 weeks and 12 months. At the same points of time all patients underwent upright, kinetic-positional MRI to measure intersegmental motion of the operated levels with determination of intervertebral angles and translation and to correlate the clinical and imaging data with each other.ResultsVAS for leg, ODI, RMDQ and physical component scale of SF-36 improved statistically significantly without statistically significant differences regarding intersegmental motion and horizontal displacement 6 weeks and 12 months after operation. Regression analysis did not find any linear dependencies between the clinical scores and imaging parameters.ConclusionsIn awareness of some limitations of the study, our results demonstrate no increase of intersegmental movement or even instability after microsurgical decompression of the lumbar spine over a follow-up period of 12 months, which is equivalent to preservation of intervertebral stability. Furthermore, the magnitude of intervertebral range of motion showed no correlation to the clinical score parameters at all three examination points of time.

Effect of different levels of segmental trunk stability training on sitting and upper limbs functions in children with bilateral spastic cerebral palsy

Background: Children with bilateral spastic cerebral palsy (BSCP) have insufficient trunk control and upper limbs (ULs) dysfunction. Purpose: to investigate the effect of segmental trunk stability training at different levels on sitting and ULs functions in children with BSCP. Subjects &amp; Methods: Thirty-nine children with BSCP, with ages ranged from 2 to 4 years, , their spasticity grade ranged from 1 to 1+ according to the Modified Ashworth Scale, their motor function was at level IV according to the Gross Motor Function Classification System – Expanded and Revised, their self-initiated ability to handle objects in daily activities with their hands was at level V according to the Mini-Manual Ability Classification System, all children’s level of segmental trunk control score ranged from 3 to 5 according to the Segmental Assessment of Trunk Control were assigned randomly to 3 groups of equal numbers, 13 children for each group. Group (A) received a specially designed physical therapy (PT) program while wearing segmental trunk support from a level just below the child’s inferior angle of the scapula to the level of his/her pelvis.

The consequence of the credit risk on the financial performance in light of COVID-19: Evidence from Islamic versus conventional banks across MEA region

PurposeThe increased number of nonperforming loans (NPLs) during COVID-19 pandemic has interrogated the robustness of banks and stability of the whole banking segment. We examine the impact of credit risk (CR) on financial performance (FP) by comparing Islamic banks (IBs) to conventional banks (CBs). We also investigate the influence of COVID-19 on this association.Design/methodology/approachOur sample includes the largest 200 banks across 15 countries from the Middle East and the Africa (MEA) region over a four-year period (2018–2021). Panel ordinary least squares (OLS) with fixed and random effects were used.FindingsWe find a negative association between NPLs and FP for IBs and CBs. We reveal that COVID-19 is partially mediated the association between NPLs and FP in case of the whole sample and separated sample of CBs while not in case of IBs.OriginalityThe evidence of CR and FP on samples of financial sector across MEA region has not been studied in the era of COVID-19 as far as we know.Research limitations/implicationsThis study contributes to the knowledge of the risk and financial performance during the crisis nexus and provides information that is valued to bankers, academics, managers and regulators for policy formulation.

Sling Exercise Can Drive Cortical Representation of the Transversus Abdominis and Multifidus Muscles in Patients With Chronic Low Back Pain.

ObjectiveThe transversus abdominis (TrA) and multifidus (MF) muscles are essential in preventing chronic low back pain (CLBP) recurrence by maintaining segmental stabilization and stiffness. Sling exercise is a high-level core stability training to effectively improve the activities of the TrA and MF muscles. However, the neural mechanism for sling exercise-induced neural plasticity change in the primary motor cortex (M1) remains unclear. This study aimed to investigate the role of sling exercise in the reorganization of the motor cortical representation of the TrA and MF muscles.MethodsTwenty patients with CLBP and 10 healthy individuals were recruited. For map volume, area, the center of gravity (CoG) location (medial-lateral location and anterior-posterior location), and latency, two-way ANOVA was performed to compare the effects of groups (the CLBP-pre, CLBP-post, and healthy groups) and the two muscles (the TrA and MF muscles). The Visual Analog Scale (VAS), the Oswestry Disability Index (ODI), and postural balance stability were assessed at baseline and at the end of 2 weeks of sling exercise. Linear correlations between VAS or ODI and CoG locations were assessed by Pearson's correlation test.Results2 weeks of sling exercise induced both the anterior-medial (P < 0.001) and anterior-posterior (P = 0.025) shifts of the MF muscle representation at the left motor cortex in patients with CLBP. Anterior-medial (P = 0.009) shift of the TrA muscle representation at the right motor cortex was observed in patients with CLBP. The motor cortical representation of the two muscles in patients with CLBP after sling exercise (TrA: 2.88 ± 0.27 cm lateral and 1.53 ± 0.47 cm anterior of vertex; MF: 3.02 ± 0.48 cm lateral and 1.62 ± 0.40 cm anterior of vertex) closely resembled that observed in healthy individuals (TrA: 2.83 ± 0.48 cm lateral and 2.00 ± 0.43 cm anterior of vertex; MF: 2.94 ± 0.43 cm lateral and 1.77 ± 0.48 cm anterior of vertex). The VAS and the ODI were reduced following the sling exercise (VAS: P < 0.001; ODI: P < 0.001).ConclusionThis study provides evidence that sling training can drive plasticity changes in the motor system, which corresponds with the reduction in pain and disability levels in patients with CLBP. This study was registered in the Chinese Clinical Trial Registry (Clinical Trial Registration Number: ChiCTR2100045904, http://www.chictr.org.cn/showproj.aspx?proj=125819).Clinical Trial RegistrationChiCTR2100045904.

Real-time assessment of anteroposterior stability of spinal segments

PurposeWhile anteroposterior instability of spinal segments is regarded as an important biomechanical aspect in the clinical evaluation of lumbar pathologies, the reliability of the available diagnostic tools is limited and an intraoperative method to quantify stability is lacking. The aim of this study was to develop and validate an instrument to measure the anteroposterior stability of a spinal segments in real-time.MethodsTorsi of five fresh-frozen human cadavers were used for this study. After pedicle screw insertion, a specifically modified reposition tool composed with load and linear sensors was used to measure the segmental anteroposterior motion caused by 100 N anterior and posterior force during 5 loading cycles on either side of the instrumentation by two different operators. The spinal segments were then resected from the torsi and anteroposterior loading with ± 100 N was repeated in an advanced biomechanical spine testing setup as a reference measurement. The Inter-correlation coefficient (ICC) was used for validation of the “intraoperative” device.ResultsInter-operator repeatability of the measurements showed an ICC of 0.93 (p < 0.0001) and the bilateral (left–right) comparison had an ICC of 0.73 (p < 0.0001). The ICC resulting from the comparison to the reference measurement was 0.82 (p < 0.0001) without offset correction, and 0.9 (p < 0.0001) with offset correction. The ICC converged at this value already after two of the five performed loading cycles.ConclusionAn accurate and reliable measurement tool is developed and validated for real-time quantification of anteroposterior stability of spinal segments and serves as a basis for future intraoperative use.

Bloch points stabilization by means of diameter modulations in cylindrical nanowires

The storage of information in long nanowires with a succession of independently oriented magnetic segments is of great practical use. It requires both the possibility of independently orienting the magnetization of each segment and great stability of the inscribed magnetization regarding spontaneous reversals. A practical way to separate sectors along the wire is by short modulations wider than the original wire that acts as a valve separating segments with independent magnetic orientations. When these two orientations are different, a Bloch Point (BP) develops within the modulation. It is precisely this BP that controls the stability of the system. In the present paper, we study the robustness of such BPs depending on geometrical parameters, such as the diameter and thickness of the cylindrical modulations as well as on external magnetic fields applied along the axis.

Unilateral versus bilateral pedicle screw fixation with transforaminal lumbar interbody fusion for treatment of lumbar foraminal stenosis

BACKGROUND CONTEXTTransforaminal lumbar interbody fusion (TLIF) with bilateral pedicle screw fixation (BPSF) is an effective treatment for lumbar foraminal stenosis (LFS). However, the effects of TLIF with unilateral pedicle screw fixation (UPSF) on LFS treatment have not been clearly elucidated. PURPOSEWe conducted this study to compare clinical outcomes and radiographic results of TLIF with UPSF and BPSF 2 years after the surgical treatment. DESIGNProspective randomized study. PATIENT SAMPLEThis study included 23 patients undergoing TLIF with UPSF and 25 patients undergoing TLIF with BPSF. OUTCOME MEASURESClinical outcomes were evaluated by visual analog scale (VAS) for low back pain and leg pain and Oswestry Disability Index (ODI) score. Radiographic outcomes included foraminal height, disc space height, segmental lordosis, and final fusion rates. METHODSThe clinical and radiographic outcomes were compared between the UPSF and BPSF group. The postoperative improvements were evaluated in either group. Intraoperative data such as duration of operation and estimated blood loss were collected. This study was registered at clinicaltrials.gov. RESULTSAnalysis of the VAS and ODI scores showed significant improvements in clinical outcomes within each group. No significant differences between the 2 groups were noted in the improvements of the VAS and ODI scores. The mean operative duration and blood loss were significantly greater in the BPSF group than in the UPSF group. There were significant improvements in the height of the foramen and intervertebral space and segmental lordosis in both groups, while there was no significant difference between the groups in amount of the improvements. No significant difference was found in the final fusion rates. CONCLUSIONSTLIF is an appropriate procedure for LFS treatment. With balanced intervertebral support using a cage, UPSF could achieve similar and satisfactory effects on lumbar segmental stability and fusion compared to BPSF. The unilateral approach appears to be associated with slightly shorter operative time and less blood loss.

Restoration of vertebral body height in traumatic thoracolumbar fractures: open versus minimal invasive surgery – which is better?

Background Percutaneous minimally invasive surgery (MIS) has been increasingly implemented to treat thoracolumbar (TL) fracture against a conventional open pedicle screw fixation (OPSF) with desirable radiological and clinical outcomes. Studies in the Indian context are required to determine the efficiency of MIS over OPSF. Objective To compare restoration and maintenance of vertebral body height (VBH) following MIS versus OPSF. Methods A prospective comparative study was conducted in a tertiary care hospital. Patients (n= 36) aged 18–65 years (males = 23, females = 13) with traumatic TL fractures were identified. Eighteen of them underwent OPSF and other eighteen underwent MIS. The radiological outcomes like anterior and posterior vertebral body height percentage (AVBH % and PVBH %) restoration and maintenance were evaluated. Quantitative variables were analyzed and described using mean ± standard deviation and qualitative variables were presented using frequency and percentage. Student t-test was used to analyse continuous data and Chi-square/Fisher Exact test was used to analyse categorical data. Results The mean age of the patients was 38.8 years. The majority of fractures were seen in the T12-LI segment (52.7 %). The AVBH % restoration and maintenance in OPSF was significantly higher compared to that of MIS at immediate post-operative (IPO) period (p = 0.01), 6 weeks (p = 0.02) and 12 weeks (p = 0.006) post-surgery. Long segment stabilization provided statistically significant AVBH and PVBH values for OPSF compared to MIS (p &lt; 0.05). The presence or absence of pedicle screw at fractured vertebral level did not restore AVBH and PVBH to a statistically significant level in both the groups (p &gt; 0.05). Superficial surgical site infection (SSSI) was seen in both the groups without any statistical significance between them (p &gt; 0.05). Conclusion OPSF is superior over MIS in the restoration of AVBH. Restoration of PVBH was also better with OPSF although not statistically significant. OPSF with longer segment fixation had better restoration of both AVBH and PVBH. The presence or absence of pedicle screw at fractured vertebral level did not seem to have any significance in both the groups. However, the MIS approach can be a reasonable alternative to open surgery with potential advantages like better clinical and functional outcome. A selected population of patients treated with MIS will show better surgical outcomes.

Biomechanical Evaluation of Seven Fixation Methods for Sagittal Split Ramus Osteotomy with Four Advancement Levels by Finite Element Analysis.

BackgroundMandibular sagittal split ramus osteotomy (SSRO) is a routine surgery to correct mandibular deformities, such as mandibular retrusion, protrusion, deficiency, and asymmetry. However, nonunion/malunion of the fragments and relapse caused by fixation failure after SSRO are major concerns. Rigid fixation to maintain postosteotomy segmental stabilization is critical for success. Additionally, understanding the biomechanical characteristics of different fixation methods in SSRO with large advancements is extremely important for clinical guidance. Therefore, the aim of the present study was to evaluate the biomechanical characteristics of different SSRO methods by finite element analysis.MethodsSSRO finite element models with 5-, 10-, 15-, and 20-mm advancements were developed. Seven fixation methods, namely, two types of bicortical screws, single miniplate, dual miniplates, grid plate, dual L-shaped plates, and hybrid fixation, were positioned into the SSRO models. Molar and incisal biomechanical loads were applied to all models to simulate bite forces. We then investigated the immediate postoperative stability from four aspects, namely, the stability of the distal osteotomy segment, osteotomy regional stability, stress distribution on the mandible, and implant stress performance.ResultsThe stability of the distal osteotomy segment and osteotomy region decreased when the advancement increased. All seven fixation methods displayed favorable biomechanical stability under minor advancement (5 mm). With large advancements, bicortical screws, dual miniplates, and grid plates provided better stability. The von Mises stress was concentrated around the screws close to the osteotomy region for the proximal segment for all fixation methods, and the von Mises stress on implants increased with larger advancements. With small advancements, five fixation methods endured tolerable maximum stresses of <880 MPa. A single miniplate and dual L-shaped plates generally suffered high stresses using larger advancements. The biomechanical characteristics were similar under molar and incisal loads.ConclusionsThe current study investigated the biomechanical properties of seven fixation devices after SSRO under molar and incisal loads. Generally, bicortical screws, grid plates, and dual miniplates provided better biomechanical stability using finite element analysis.

Effects on the emission of different interfaces formed between poly(3-methylthiophene) and poly(3-octylthiophene): electrochemical impedance and photoluminescence spectroscopy studies

With the aim of verifying the optical properties of the systems formed by poly(3-methylthiophene) (P3MT) and poly(3-octylthiophene) (P3OT) on platinum (Pt) for use in organic photovoltaic device applications, electrochemical preparations of different interfaces with poly(3-alkylthiophenes) (P3ATs), synthesized both with 18 °C and without temperature control, were compared. These interfaces were prepared both as blends (Pt/P3MT:P3OT) and as layered films (Pt/P3MT/P3OT and Pt/P3OT/P3MT). Electrochemical impedance spectroscopy (EIS) was used to characterize the systems, and based on Bode-Phase diagrams, it was possible to monitor the stabilization of radical cation and dication segments of the thiophene ring. The findings corroborated previous studies by electrochemical spectroscopy and using in situ Raman spectroscopy under the same experimental conditions. We were able to verify the effects of experimental variables, such as synthesis temperature and different kinds of deposition. Temperature was found to be an extremely important factor in synthesis, since films synthesized at 18 °C favored the stabilization of radical cation segments in the polymer matrix, and layered deposition also favored the stabilization of these segments, since the layer closest to the electrode can act as an induction layer for the stability of radical cation segments in the system. Photoluminescence spectroscopy was used to verify the optical properties of the interfaces, in which occur the contributions of three segments in the P3ATs matrix. Thus, it has been demonstrated through photoluminescence decay time that the relative amount of radical cation and dication segments in the polymer matrix affects the lifetime of these segments in the different materials prepared, due to emission effects for these systems.

Geographic Approach: Identifying Relatively Stable Tibetan Dialect and Subdialect Area Boundaries

Updating dialect maps requires extensive language surveys. Geographic methods can be applied to identify relatively stable boundaries of dialect and subdialect areas, allowing language surveys to focus on boundaries that may change and thereby reduce survey costs. Certain scholars have pointed out that the watershed boundary can be employed as the boundary of Tibetan dialect areas. This paper adds that the lowest-grade road breakpoint line and no-man’s-land boundary can also be used as essential indicators for determining stable (sub)dialect area boundaries. Combined with the revised First Law of Geography and the method of superposition analysis of geographic elements, this study identifies indicators that affect the stability of the Tibetan (sub)dialect area boundaries and evaluates the stability of each boundary segment. Due to the particularity of the study area, most Qinghai–Tibet Plateau (Chinese part) (sub)dialect area boundaries are stable. In addition, boundary inaccuracies caused by defects in the distribution of language survey samples can be identified by geographic approaches.

Autologous Mesenchymal Stromal Cells Combined with Gelatin Sponge for Repair Intervertebral Disc Defect after Discectomy: A Preclinical Study in a Goat Model.

The defect of intervertebral disc (IVD) after discectomy may impair tissue healing and predispose patients to subsequent IVD degeneration, which is thought to be an important cause of recurrence. Cell-based approaches for the treatment of IVD degeneration have shown promise in preclinical studies. However, most of these therapies have not been approved for clinical use due to the risks of abnormal differentiation and microorganism contamination of the culture-expanded cells. Selective cell retention (SCR) technology is non-cultivation technique, which can avoid those preambles in cell expansion. In this study, we used a commercially available BONE GROWTH PROMOTER device (BGP, FUWOSI, Chongqing, China) to concentrate mesenchymal stromal cells (MSCs) from bone marrow aspirate (BMA) through SCR technology. A small incision was made on the L2/3, L3/4 and L4/5 discs of goats and part of nucleus pulposus (NP) was removed to construct IVD defect model. The L2/3 disc was subjected to discectomy only (DO group), the L3/4 disc was implanted with enriched BMA-matrix (CE group), and the L4/5 disc was implanted cultured autologous bone marrow MSCs matrix (CC group). And the intact L1/2 disc served as a non-injured control (NC group). The animals were followed up for 24 weeks after operation. Spine imaging was analysis performed at 4 and 24 weeks. Histology, immunohistochemistry, gene expression and biomechanical analysis were performed to investigate the IVD morphology, content and mechanical properties at 24 weeks. The CE and CC groups showed a significantly smaller reduction in the disc height and T2-weighted signal intensity, and a better spinal segmental stability than DO group. Histological analysis demonstrated that CE and CC groups maintained a relatively well-preserved structure compared to the DO group. Furthermore, real-time PCR and immunohistochemistry demonstrated that aggrecan and type II collagen were up-regulated in CE and CC groups compared to DO group. The strategy of MSCs enrichment combined with gelatin sponge by SCR technology provides a rapid, simple, and effective method for cell concentration and cell-carrier combination. This reparative strategy can be used in clinical treatment of IVD defect after discectomy. NCT03002207.

Research progress of spontaneous facet fusion after lumbar spine surgery

To summarize the research progress on spontaneous facet fusion (SFF) after lumbar spine surgery, and provide reference for further research on SFF. The definition, development, clinical significance, and related influence factors of SFF were throughout reviewed by referring to relevant domestic and foreign literature in recent years. SFF is a phenomenon of joint space disappearance and fusion of upper and lower articular processes, which starts in a ring shape from the outermost edges to the central regions. Currently reported SFF occurred after posterior lumbar pedicle screw fixation. SFF may increase the stability of surgical segments and relieve clinical symptoms of patients. SFF is closely related to the method of lumbar internal fixation, facet osteoarthritis, interbody fusion, age, body mass index, type B fracture (according to AO classification), and the operative segment. Most reported SFF occur after posterior lumbar pedicle screw fixation, which can increase lumbar stability, but the mechanism and influencing factors remain to be further clarified.

Postoperative Paraspinal Muscles Assessment After Endoscopic Stenosis Lumbar Decompression: Magnetic Resonance Imaging Study.

Conventional open lumbar decompression is a widely accepted procedure for degenerative lumbar disease. However, it is associated with morbidity due to damage to the paraspinal muscles and posterior ligamentous complex. Endoscopic spine surgery (ESS) is considered the least invasive type of spine surgery in modern times and was developed to minimize the iatrogenic injury to the paraspinal muscles. Many studies are reported to estimate the paraspinal muscle damage after an open or minimal invasive spine surgery by radiological methods (magnetic resonance imaging [MRI] and computed tomography], biochemistry (creatinine phosphokinase level), or electrophysiology (electoneuromyography). The objectives of this study were to assess paraspinal muscles changes after lumbar endoscopic unilateral laminotomy with bilateral decompression (LE-ULBD) based on preoperative and 6-month postoperative MRIs. We studied 159 consecutive patients with lumbar degenerative disease who underwent LE-ULBD at a spine specialty hospital from 2018 to 2019. The current study was a single-center, single-surgeon, retrospective case study. Changes of paraspinal muscles after LE-ULBD measured on lumbar MRI. Postoperative paraspinal muscles changes are evaluated on a picture archiving and communication system by measuring the cross-sectional area (CSA) of multifidus and erector spinae muscles along with the fatty infiltration of muscle on Kjaer's scale at the level of surgery on the ipsilateral and contralateral sides on T1W image. Correlations between imaging and visual analog scale (VAS) score for back, Oswestry Disability Index (ODI), and MacNab's criteria were examined in the preoperative and postoperative periods. Of the 159 patients included, 120 underwent a single level procedure and 39 a multilevel procedure. For single-level LE-ULBD group, mean (SD) preoperative, postoperative, and final follow-up VAS score (7.83 [1.37], 3.15 [0.67] and 2.19 [0.88]; P < 0.001) and ODI (74.09 [7.18], 27.88 [4.40], and 23.88 [4.56]; P < 0.001) improved significantly. Based on MacNab's criteria, the clinical result was excellent in 37 patients, good in 78 patients, and fair in 5 patients. For the multilevel LE-ULBD group, the mean (SD) preoperative, postoperative, and final follow-up VAS score (7.84 [1.38], 3.50 [0.60],and 2.44 [0.79]; P < 0.001) and ODI (74.1 [7.72], 31.30 [4.46], and 24.90 [4.75]; P < 0.001) also improved significantly . Based on MacNab's criteria, the clinical result was excellent in 6 patients, good in 31 patients, and fair in 2 patients.The functional CSA of paraspinal muscles for both groups showed no significant difference in the 6-month follow-up MRI. The fatty infiltration of paraspinal muscles significantly improved from 0.77 to 0.59 (P < 0.05) for the single level LE-ULBD group but not for the multilevel LE-ULBD group (P = 0.320). The mean dural sac CSA increased significantly for both groups (P < 0.001). Adequate neural decompression can be achieved with the preservation of paraspinal muscles after an ESS. Preservation of the paraspinal muscles along with the posterior ligamentous complex improves the stability of motion segment in the postoperative period, which ultimately results in better patient outcomes in related to postoperative pain and rehabilitation.Key.

Numerical Simulation of Dimensional Stability of Precast Segments Exposed to Solar Radiation During Yard Storage

Numerical Simulation of Dimensional Stability of Precast Segments Exposed to Solar Radiation During Yard Storage

Redundant apodization for direct imaging of exoplanets

Context. Direct imaging and spectroscopy of Earth-like planets and young Jupiters require contrast values up to 106−1010 at angular separations of a few dozen milliarcseconds. To achieve this goal, one of the most promising approaches consists of using large segmented primary mirror telescopes with coronagraphic instruments. While they are able to reach high contrast at small angular separations, coronagraphs are highly sensitive to wavefront errors, however. The segmentation itself is responsible for phasing errors and segment-level vibrations that have to be controlled at a subnanometric accuracy. Aims. We propose an innovative method for a coronagraph design that allows a consequent relaxation of the segment phasing and stability constraints for low segment-count mirrors and generates an instrument that is more robust to segment-level wavefront errors. Methods. This method is based on an optimization of the coronagraph design that includes a segment-level apodization. This is repeated over the pupil to match the segmentation redundancy and improves the contrast stability beyond the minimum separation set by the single-segment diffraction limit. Results. We validate this method on a Giant Magellan Telescope (GMT)-like pupil (seven circular segments) for two coronagraph types: apodized pupil Lyot coronagraphs, and apodizing phase plate coronagraphs. For the apodized pupil Lyot coronagraphs, redundant apodization enables releasing the piston phasing constraints by a factor of 5-20 compared to classical designs. For the apodizing phase plate coronagraphs, the contrast remains almost constant up to 1 radian RMS of the phasing errors. We also show that redundant apodizations increase the robustness of the coronagraph to segment tip-tilt errors, as well as to missing segment errors. Conclusions. Redundant apodization enables reducing or even removing any constraints on the primary mirror segment phasing at the price of larger angular separations and lower throughputs. This method cannot be applied to higher-segment count mirrors such as the ELT or the TMT, but it is particularly suitable for low segment-count mirrors (fewer than ~20 segments) such as the GMT aperture. These mirrors aim for high-contrast imaging of debris disks or exoplanets down to 100 mas.

Influence of Aqueous Arginine Solution on Regulating Conformational Stability and Hydration Properties of the Secondary Structural Segments of a Protein at Elevated Temperatures: A Molecular Dynamics Study.

The effects of aqueous arginine solution on the conformational stability of the secondary structural segments of a globular protein, ubiquitin, and the structure and dynamics of the surrounding water and arginine were examined by performing atomistic molecular dynamics (MD) simulations. Attempts have been made to identify the osmolytic efficacy of arginine solution, and its influence in guiding the hydration properties of the protein at an elevated temperature of 450 K. The similar properties of the protein in pure water at elevated temperatures were computed and compared. Replica exchange MD simulation was performed to explore the arginine solution's sensitivity in stabilizing the protein conformations for a wide range of temperatures (300-450 K). It was observed that although all the helices and strands of the protein undergo unfolding at elevated temperature in pure water, they exhibited native-like conformational dynamics in the presence of arginine at both ambient and elevated temperatures. We find that the higher free energy barrier between the folded native and unfolded states of the protein primarily arises from the structural transformation of α-helix, relative to the strands. Our study revealed that the water structure around the secondary segments depends on the nature of amino acid compositions of the helices and strands. The reorientation of water dipoles around the helices and strands was found hindered due to the presence of arginine in the solution; such hindrance reduces the possibility of exchange of hydrogen bonds that formed between the secondary segments of protein and water (PW), and as a result, PW hydrogen bonds take longer time to relax than in pure water. On the other hand, the origin of slow relaxation of protein-arginine (PA) hydrogen bonds was identified to be due to the presence of different types of protein-bound arginine molecules, where arginine interacts with the secondary structural segments of the protein through multiple/bifurcated hydrogen bonds. These protein-bound arginine formed different kinds of bridged PA hydrogen bonds between amino acid residues of the same secondary segments or among multiple bonds and helped protein to conserve its native folded form firmly.

Residual stability of the craniovertebral segment in its various injuries

Residual stability of craniovertebral segment in the most common injuries (odontoid process fractures, ring fractures of C2, Atlas fractures, etc.) was sudied in experiment. The study was performed in 7 cadaveral craniovertebral blocks. The range of movement before and after injuires modelling, the estimation of force that caused the vertebrae displacement using special loading test device were detected. It was shown that in any injury without vertebrae dislocation craniovertebral segment possessed the residual stability. The minor stability was noted in odontoid prosess fractures of II and III types and butchersfractures, the major stability was in the intervertebral disc injuries of C2-C3 and occipital condyle fractures. On the base of experimental and clinical data the conclusion was done that fixation of cervical spine using head support with frontal fixative or halo apparatus were indicated for cranivertebral segement injuries without vertebrae dislocation. In dislocation of vertebrae it was necessary to reduce the dislocation and open surgical intervention for stabilization.

Biomechanical comparison of vertebral augmentation and cement discoplasty for the treatment of symptomatic Schmorl’s node: a finite element analysis

ABSTRACT Percutaneous vertebral augmentation (PVA) and percutaneous cement discoplasty (PCD) are two relatively new minimally invasive surgeries for symptomatic Schmorl's reported in recent decade. However, the clinical evidence for the effectiveness of these two surgeries is insufficient. The purpose of this study was to compare the biomechanical benefits and risks of the two surgeries in order to analyze their biomechanical differences and effectiveness. We reconstructed Five lumbar finite element models via computed tomography data, including control model, PVA-ideal model, PVA-nonideal model, PCD-ideal model, and PCD-nonideal model. The stress and strain of Schmorl's nodes, bone marrow edema zone (BMEZ), affected endplate, and the overall stability of segment were analyzed and compared. The validity of our models was confirmed. As a result, the PVA-ideal model can significantly reduce the stress of Schmorl's node and the strain of BMEZ, while this effect is inappreciable in PVA-nonideal model. The PCD-ideal model significantly reduced the strain of Schmorl's nodes and BMEZ, and significantly improve segmental stability, but also resulted in a significant increase in the stress of Schmorl's nodes, BMEZ and endplates. The PCD-nonideal model not only lacks blocking effect, but also sharply increases the strain of Schmorl's nodes and BMEZ. Thus, We recommend that both PVA and PCD surgeries in ideal distribution facilitated a more stable paranodular biomechanical microenvironment. However, due to the possibility of poor biomechanical outcomes caused by the non-ideal cement distribution, the non-ideal distribution of bone cement needs to be remedied in practice.