One-Step Manufacturing of Supramolecular Liquid-Crystal Elastomers by Stress-Induced Alignment and Hydrogen Bond Exchange.

Liquid-crystal elastomers (LCEs) capable of performing large and reversible deformation in response to an external stimulus are an important class of soft actuators. However, their manufacturing process typically involves a multistep approach that requires harsh conditions. For the very first time, LCEs with customized geometries that can be manufactured by a rapid one-step approach at room temperature are developed. The LCEs are hydrogen bond (H-bond) crosslinked main chain polymers comprising flexible short side chains. Applying a stretching/shear force to the LCE can simultaneously induce mesogen alignment and H-bond exchange, allowing for the formation of well-aligned LCE networks stabilized by H-bonds. Based on this working principle, soft actuators in fibers and 2D/3D objects can be manufactured by mechanical stretching or melt extrusion within a short time (e.g. <1 min). These actuators can perform reversible macroscopic motions with large, controlled deformations up to 38 %. The dynamic nature of H-bonds also provides the actuators with reprocessability and reprogrammability. Thus, this work opens the way for the one-step and custom manufacturing of soft actuators.

Visible-light activatable coumarin-based phototriggers for fluorescence imaging with ultra-high photolysis efficiency.

Photoactivated fluorophores (PAFs) are powerful imaging tools for observing subcellular structures and tracking dynamic biological processes. However, photoremovable protecting groups (PPGs) widely used to construct PAFs suffer from the drawbacks of short-wavelength excitation and/or low photolysis efficiency. Herein, a class of coumarin-based PPGs with electron-rich thiophene derived substitutions at the C3-position of a coumarin scaffold were prepared. The modification not only leads to the redshift of the absorption band to the blue light region (400-500 nm), but also the increases of uncaging quantum yield (Φu) as well as molar extinction coefficient (εmax), thus enhancing the photolysis efficiency (Φu × Îµmax) up to 34.2 × 103 M-1 cm-1. The exceptionally high photolysis efficiency enables efficient photolysis in blue light as weak as 2 mW cm-2 or in blue light from a Luminol chemiluminescence system. Based on the excellent photolysis properties, the PAF constructed by the new PPG exhibits fast photoactivation and a low background signal, and the resulting fluorescence images display a signal-to-noise ratio greater than 780. It is anticipated that the superior photolysis performance makes the PPGs a novel platform for the construction of photo responsive systems in a variety of applications.

Roles of p38 MAPK signalling in intervertebral disc degeneration.

Intervertebral disc degeneration (IVDD) is a common degenerative disease mediated by multiple factors. Because of its complex aetiology and pathology, no specific molecular mechanisms have yet been identified and no definitive treatments are currently available for IVDD. p38 mitogen-activated protein kinase (MAPK) signalling, part of the serine and threonine (Ser/Thr) protein kinases family, is associated with the progression of IVDD, by mediating the inflammatory response, increasing extracellular matrix (ECM) degradation, promoting cell apoptosis and senescence and suppressing cell proliferation and autophagy. Meanwhile, the inhibition of p38 MAPK signalling has a significant effect on IVDD treatment. In this review, we first summarize the regulation of p38 MAPK signalling and then highlight the changes in the expression of p38 MAPK signalling and their impact on pathological process of IVDD. Moreover, we discuss the current applications and future prospects of p38 MAPK as a therapeutic target for IVDD treatment.

Does the Choice of Operative Side Affect the Clinical Outcome of Unilateral Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fracture?

BACKGROUND: Studies have found that the rate of improvement in pain after percutaneous kyphoplasty (PKP) is 49% to 90%, and there are still some patients who may continue to sustain intractable back pain after surgery. OBJECTIVES: To compare the clinical efficacy and imaging results between unilateral PKP performed from the symptom-dominating side and the non-dominating side in OVCF treatment. STUDY DESIGN: Prospective study. SETTING: All data were from Honghui Hospital in Xi'an. METHODS: One hundred forty-two patients of osteoporotic vertebral compression fracture (OVCF) treated with unilateral PKP were eventually recruited and randomly assigned to either the A or B group. Patients in group A received PKP from the symptom-dominating side; patients in group B received PKP from the symptom non-dominating side. The demographic characteristics, related surgical information, and complications observed within both groups were recorded. The clinical outcomes evaluation included the visual analog scale (VAS) score for low back pain and the Oswestry Disability Index (ODI). Evaluation of imaging results included anterior height (AH), kyphosis angulation (KA), and contralateral distribution rate of bone cement. RESULTS: One hundred eighteen patients (48 men and 70 women; age range: 60-83 years), including 59 patients in the A group and 59 patients in the B group, were available for the complete assessment. There were 5 cases and 7 cases of bone cement leakage in groups A and B, respectively, which were asymptomatic para-vertebral or inter-vertebral leakage without intra-spinal leakage. Compared with the preoperative data, significant improvements in the VAS scores and ODI were observed at each follow-up interval. The VAS score and ODI in the A group were significantly lower than in the B group only within 2 months (P < 0.05). Compared with the preoperative data, the AH and KA in the 2 groups were improved (P < 0.05). There was no significant difference in AH and KA between the 2 groups at each follow-up interval (P > 0.05). LIMITATIONS: A single-center study. CONCLUSIONS: The unilateral PKP performed via the symptom-dominating side can effectively relieve back pain and improve the patient's quality of life at the early stage.

Progress in Chemical Recycling of Carbon Fiber Reinforced Epoxy Composites.

Carbon fiber reinforced polymer (CFRP) composites are indispensable in a variety of applications, because of their high specific strength. CFRPs are generally constructed by carbon fibers as reinforcements and crosslinked polymers as binders. Due to the irreversible nature of the crosslinked polymers, CFRPs are neither repairable nor recyclable. Once the material is damaged or out of service, landfill or incineration is the typical way to deal with the waste. These methods take no advantages of the residue value of the waste and add burdens to the environment. To reduce waste and cost, it is desirable to develop effective recycling technologies to reserve the residue value of carbon fiber and polymer matrix. In the past decade, chemical recycling by cleaving the covalent bonds in a solvent has been considered as an ideal path for the recycling of CFRP wastes, because it has the potential to recover both valuable CFs and polymer matrix. In this review, the discussion is focused on the progress in the chemical recycling of CFRP. The primary matrix resin of CFRP discussed in this review is epoxy resin which is the most widely used polymer matrix. In addition, the challenges and outlook are provided.

Risk factors for proximal junctional kyphosis after posterior long-segment internal fixation for chronic symptomatic osteoporotic thoracolumbar fractures with kyphosis.

BACKGROUND: This study aimed to analyze the risk factors for proximal junctional kyphosis (PJK) for patients with chronic symptomatic osteoporotic thoracolumbar fractures (CSOTLF) and kyphosis who underwent long-segment internal fixation. METHODS: We retrospectively reviewed the records of patients with CSOTLF complicated with kyphosis who underwent posterior multilevel internal fixation in our hospital between January 2013 and January 2020. The patients' age, sex, body mass index (BMI), bone mineral density (BMD), smoking status, cause of injury, comorbidities, injury segments, and American Spinal Injury Association (ASIA) grading non-surgical data; posterior ligament complex (PLC) injury, upper and lower instrumented vertebral position (UIV and LIV, respectively), number of fixed segments surgical data, proximal junctional angle (PJA), sagittal vertebral axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) surgical indicators were collected. Patients were divided into postoperative PJK and non-PJK groups. RESULTS: This study included 90 patients; among them, 30 (31.58%) developed PJK postoperatively. All patients were followed up for > 24 months (mean 32.5 months). Univariate analysis showed significant differences in age, BMI, BMD, PLC injury, UIV, and LIV fixation position, number of fixation stages, and preoperative PJA, SVA, PI-LL, and SS between the two groups (P < 0.05). Additionally, no significant differences were observed in sex, smoking, cause of injury, complications, injury segment ASIA grade, and preoperative PT between the two groups (P > 0.05). Multifactorial logistic regression analysis showed that age > 70 years (OR = 32.279, P < 0.05), BMI > 28 kg/m2 (OR = 7.876, P < 0.05), BMD T value < - 3.5 SD (OR = 20.836, P < 0.05), PLC injury (OR = 13.981, P < 0.05), and preoperative PI-LL > 20° (OR = 13.301, P < 0.05) were risk factors for PJK after posterior long-segment internal fixation in elderly patients with CSOTLF complicated with kyphosis. CONCLUSION: CSOTLF patients undergoing posterior long segment internal fixation are prone to PJK, and age > 70 years, BMI > 28 kg/m2, BMD T value < - 3.5 SD, preoperative PI-LL > 20° and PLC injury may increase their risk.

Liquid Crystalline Elastomers Based on Click Chemistry.

Liquid crystalline elastomers (LCEs) have emerged as an important class of functional materials that are suitable for a wide range of applications, such as sensors, actuators, and soft robotics. The unique properties of LCEs originate from the combination between liquid crystal and elastomeric network. The control of macroscopic liquid crystalline orientation and network structure is crucial to realizing the useful functionalities of LCEs. A variety of chemistries have been developed to fabricate LCEs, including hydrosilylation, free radical polymerization of acrylate, and polyaddition of epoxy and carboxylic acid. Over the past few years, the use of click chemistry has become a more robust and energy-efficient way to construct LCEs with desired structures. This article provides an overview of emerging LCEs based on click chemistries, including aza-Michael addition between amine and acrylate, radical-mediated thiol-ene and thiol-yne reactions, base-catalyzed thiol-acrylate and thiol-epoxy reactions, copper-catalyzed azide-alkyne cycloaddition, and Diels-Alder cycloaddition. The similarities and differences of these reactions are discussed, with particular attention focused on the strengths and limitations of each reaction for the preparation of LCEs with controlled structures and orientations. The compatibility of these reactions with the traditional and emerging processing techniques, such as surface alignment and additive manufacturing, are surveyed. Finally, the challenges and opportunities of using click chemistry for the design of LCEs with advanced functionalities and applications are discussed.

Comparison of degenerative lumbar spondylolisthesis and isthmic lumbar spondylolisthesis: effect of pedicle screw placement on proximal facet invasion in surgical treatment.

BACKGROUND: Pedicle screw invasion of the proximal articular process will cause local articular process degeneration and acceleration, which is an important factor affecting adjacent segment degeneration. Although lumbar spondylolisthesis is a risk factor for screw invasion of the proximal joint, there is no clear conclusion regarding the two different types of spondylolisthesis. Therefore, the purpose of this study was to explore the influence of pedicle screw placement on proximal facet invasion in the treatment of degenerative spondylolisthesis and isthmic spondylolisthesis. METHODS: In total, 468 cases of lumbar spondylolisthesis treated by decompression and fusion in our hospital from January 2017 to January 2020 were included in this retrospective study. Among them, 238 cases were degenerative spondylolisthesis (group A), and 230 cases were isthmic spondylolisthesis (group B). Sex, age, body mass index, bone mineral density, preoperative visual analog scale (VAS) and Oswestry Disability Index (ODI) scores, postoperative VAS and ODI scores at 1 month and 3 months, and angle of the proximal facet joint at the last follow-up were recorded and compared between the two groups. The degree of pedicle screw invasion of the proximal facet joint was graded and compared by the SEO grading method. RESULTS: There were no significant differences in sex, age, body mass index, bone mineral density, preoperative VAS and ODI scores, or proximal facet joint angle between the two groups (P > 0.05). There was no significant difference in VAS and ODI scores between the two groups at 1 month and 3 months after the operation (P > 0.05). The VAS score of group A at the last follow-up was 1 (1,2). The VAS score of group B at the last follow-up was 3 (1,3). The ODI score of group A at the last follow-up was 6(4,26). The ODI score of group B at the last follow-up was 15(8,36). The VAS and ODI scores of the two groups at the last follow-up were significantly different (P < 0.05). According to the SEO grading method, the invasion of the proximal articular process by pedicle screw placement in group A involved 320 cases in grade 0, 128 cases in grade I and 28 cases in grade II. In group B, there were 116 cases in grade 0, 248 cases in grade I and 96 cases in grade II, with a significant difference (P < 0.01). CONCLUSION: In summary, a certain number of cases involving screws invading the proximal facet joint occurred in the two different types of lumbar spondylolisthesis, but the number in the isthmic spondylolisthesis group was significantly higher than that in the degenerative spondylolisthesis group, which caused more trauma to the proximal facet joint and significantly affected the patient prognosis.

Multivariate analysis of pedicle screw invasion of the proximal facet joint after lumbar surgery.

BACKGROUND: To analyze the risk factors for pedicle screw invasion of the proximal facet joint after lumbar surgery. METHODS: From January 2019 to January 2021, 1794 patients with lumbar degenerative disease, such as lumbar disc herniation, lumbar spinal stenosis and lumbar spondylolisthesis, were treated at our hospital. In all, 1221 cases were included. General data (sex, age, BMI), bone mineral density, proximal facet joint angle, degenerative lumbar spondylolisthesis, isthmic lumbar spondylolisthesis and fixed segment in the two groups were recorded. After the operation, vertebral CT of the corresponding surgical segments was performed for three-dimensional reconstruction and evaluation of whether the vertebral arch root screw interfered with the proximal facet joint. The included cases were divided into an invasion group and a noninvasion group. Univariate analysis was used to screen the risk factors for pedicle screw invasion of the proximal facet joint after lumbar surgery, and the selected risk factors were included in the logistic model for multivariate analysis. RESULTS: The single-factor analysis showed a significant difference in age, BMI, proximal facet joint angle, degenerative lumbar spondylolisthesis, and fixed segment (P < 0.1). Multifactor analysis of the logistic model showed a significant difference for age ≥ 50 years (P < 0.001, OR = 2.291), BMI > 28 kg/m2 (P < 0.001, OR = 2.548), degenerative lumbar spondylolisthesis (P < 0.001, OR = 2.187), gorge cleft lumbar relaxation (P < 0.001, OR = 2.410), proximal facet joint angle (35 ~ 45°: P < 0.001, OR = 3.151; > 45°: P < 0.001, OR = 3.578), and fixed segment (lower lumbar spine: P < 0.001, OR = 2.912). CONCLUSION: Age (≥ 50 years old), BMI (> 28 kg/m2), proximal facet joint angle (35 ~ 45°, > 45°), degenerative lumbar spondylolisthesis, isthmic lumbar spondylolisthesis and fixed segment (lower lumbar spine) are independent risk factors for pedicle screw invasion of the proximal facet joint after lumbar surgery. Compared with degenerative lumbar spondylolisthesis, facet joint intrusion is more likely in isthmic lumbar spondylolisthesis.

Risk Factors for New Vertebral Fracture After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures.

PURPOSE: To analyze the risk factors for new vertebral fractures after percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs). PATIENTS AND METHODS: We retrospectively reviewed the records of patients with symptomatic OVCFs who underwent PVP in our hospital, from January 2014 to January 2019. Demographic and lifestyle data on the presence of underlying chronic disease, preoperative bone mineral density, details of vertebral fractures, postoperative osteoporosis treatment, and new fracture development were collected. Patients were divided into postoperative fracture and non-fracture groups. To identify the independent risk factors for new vertebral fracture development, variables significant on univariate analysis were included in a multivariate regression model. RESULTS: Of the 2202 patients treated with PVP, 362 (16.43%) had a new postoperative vertebral fracture. All patients were followed up for >12 months (mean 14.7 months). Univariate analysis revealed no significant difference in height; body weight; preoperative bone mineral density; number of fractured vertebrae; injection volume of bone cement in a single vertebra; leakage rate of bone cement; or presence of hypertension, coronary heart disease, and chronic obstructive pulmonary disease between the fracture and non-fracture groups (P>0.05). Age, sex, smoking, alcohol consumption, diabetes mellitus, postoperative exercise, and postoperative osteoporosis treatment were associated with new vertebral fractures (all P<0.05). A multivariate analysis showed that age (odds ratio [OR]=1.212, P<0.0001), female sex (OR=1.917, P<0.0001), smoking (OR=1.538, P=0.026), and diabetes (OR=1.915, P<0.0001) were positively correlated with new vertebral fracture development, whereas postoperative exercise (OR=0.220, P<0.0001) and osteoporosis treatment (OR=0.413, P<0.0001) were negatively correlated. CONCLUSION: Elderly patients, females, and those with a history of smoking and diabetes are at high risk of new vertebral fracture after PVP. Patients should be encouraged to stop smoking and consuming alcohol, control blood glucose level, participate in sufficient physical activity, and adhere to osteoporosis treatment to prevent new vertebral fractures.

Posterior Ligament-Bone Injury Classification and Severity Score: A Novel Approach to Predict the Failure of Anterior-only Surgery for Subaxial Cervical Facet Dislocations.

STUDY DESIGN: Clinical case series. OBJECTIVE: The aim of this study was to propose a novel posterior ligament-bone injury classification and severity (PLICS) score system that can be used to reflect the severity of subaxial cervical fracture dislocations (SCFDs) and predict the failure of anterior-only surgery; and to measure the intraobserver and interobserver reliability of this system. SUMMARY OF BACKGROUND DATA: The approach selection for SCFDs is controversial. Although the anterior approach is familiar for most surgeons, postoperative hardware failure and/or delayed cervical deformity is a nonnegligible complication. METHODS: Ten patients were randomly selected for intraobserver reliability evaluation on two separate occasions, one month apart. Another 30 patients were randomly selected, and the interobserver reliability was measured by comparing results of each case between each reviewer and averaging. To analyze the difference in the PLICS score, 354 patients fulfilled the follow-up were divided into stable and unstable groups according to whether radiologically stable was observed during follow-up. RESULTS: For the intraobserver reliability, the mean intraclass correlation coefficient for the 10 reviewers was 0.931. For the interobserver reliability, the mean interobserver correlation coefficient for the three elements was 0.863. Among 16 patients with PLICS score ≥7, two patients in the stable group manifested with severe injury of the posterior ligamentous complex (PLC); extremely unstable lateral mass fractures with or without severe injury of PLC were detected in the 14 patients of the unstable group. CONCLUSION: The proposed PLICS score system showed excellent intraobserver and interobserver reliability. When a PLICS score is >7 or 7 accompanied by extremely unstable lateral mass fractures, the risk of postoperative failure after an anterior-only reconstruction is high and supplemental posterior strengthening can be considered.Level of Evidence: 4.

When is the circumferential stabilization necessary for subaxial cervical fracture dislocations? The posterior ligament-bone injury classification and severity score: a novel treatment algorithm.

OBJECTIVE: To propose a novel classification and scoring system called the posterior ligament-bone injury classification and severity score (PLICS) that offers a quantitative score to guide the need for posterior stabilization in addition to anterior reconstruction for subaxial cervical fracture dislocations (SCFDs). METHODS: A total of 456 patients with SCFDs were prospectively included. Patients with PLICS ≥ 7 together with extremely unstable lateral mass fracture (EULMF) were classified as high-risk group, and the other patients were classified as low-risk group. For patients in the low-risk group, anterior-only reconstruction was performed; for patients in the high-risk group, additional posterior lateral mass fixation and fusion was performed after anterior reconstruction. Clinical outcome evaluation included using the visual analogue score (VAS), the Neck Disability Index (NDI), and the American Spinal Injury Association (ASIA) impairment scale. The change in the local sagittal alignment kyphosis Cobb angle was also recorded. RESULTS: A total of 370 patients (81.1%) completed the minimal 12-month follow-ups, including 321 patients of low-risk group and 49 patients of high-risk group. Compared with the average VAS score preoperatively, the score at 12-month follow-up was significantly improved (from 6.1 + 0.3 to 1.1 + 0.2 in the low-risk group, P < 0.001; from 6.4 + 0.2 to 1.4 + 0.2 in the high-risk group, P < 0.001). The average NDI score at the 12-month follow-up was statistically low in the low-risk group (8.8 + 2.5 vs 13.8 + 3.4, P = 0.034). At least more than one grade improvement in the ASIA scale was observed in 80.5% of all patients. The local kyphosis Cobb angle at the injured segment averaged improved in both groups. CONCLUSION: A PLICS score ≥ 7 together with EULMF can be the threshold for posterior stabilization in addition to anterior reconstruction for the patients with SCFDs.

Carbon Fiber Reinforced Epoxy Vitrimer: Robust Mechanical Performance and Facile Hydrothermal Decomposition in Pure Water.

Conventional carbon fiber reinforced thermosetting polymers (CFRPs) are neither recyclable nor repairable due to their crosslinked network. The rapid growing CFRP market raises a serious concern of the waste management. In this work, a viable method to develop a readily recyclable CFRP based on epoxy vitrimer is introduced. First, a self-catalytic epoxy prepolymer with built-in hydroxy and tertiary amine groups is designed, which upon reaction with an anhydride formed a catalyst-free epoxy vitrimer. The epoxy prepolymer is synthesized from a diamine and an excess of bisphenol A epoxy resin. The hydroxyls and tertiary amines of the epoxy prepolymer efficiently catalyze both curing and the dynamic transesterification of the crosslinked polymer without the need of a catalyst. Then, the epoxy vitrimer is used as the matrix resin to prepare CFRP. The resulting CFRP exhibited a tensile strength as high as 356 MPa. More interestingly, the matrix of the CFRP is efficiently degraded in pure water at above 160 °C. This is because the built-in tertiary amines catalyze the hydrolysis of the ester bonds of the crosslinked network. The simple method developed in this work provides a framework for the development of recyclable CFRP.

Comparison of robot-assisted and freehand pedicle screw placement for lumbar revision surgery.

BACKGROUND: The accuracy of robot-assisted pedicle screw implantation is a safe and effective method in lumbar surgery, but it still remains controversial in lumbar revision surgery. This study evaluated the clinical safety and accuracy of robot-assisted versus freehand pedicle screw implantation in lumbar revision surgery. METHODS: This was a retrospective study. From January 2018 to December 2019, 81 patients underwent posterior lumbar revision surgery in our hospital. Among them, 39 patients underwent revision surgery performed with robot-assisted pedicle screw implantation (Renaissance robotic system), whereas the remaining 42 patients underwent traditional freehand pedicle screw implantation. All patients underwent magnetic resonance imaging (MRI), computed tomography (CT), and X-ray before revision surgery. The sex, age, body mass index, bone mineral density, operative time, blood loss, operative segments, intra-operative fluoroscopy time, and complications were compared between the two groups. The accuracy of pedicle screw implantation was measured on CT scans based on Gertzbein Robbins grading, and the invasion of superior level facet joint was evaluated by Babu's method. RESULTS: There was no statistical difference about the baseline between the two groups (P > 0.05). Although there were no significant differences in operative time and complications between the two groups (P > 0.05), the robot-assisted group had significantly less intra-operative blood loss and shorter intra-operative fluoroscopy times than the freehand group (P < 0.05). In the robot-assisted group, a total of 267 screws were inserted, which were marked as grade A in 250, grade B in 13, grade C in four, and no grade D or E in any screw. In terms of invasion of superior level facet joint, a total of 78 screws were inserted in the robot-assisted group, which were marked as grade 0 in 73, grade 1 in four, grade 2 in one, and grade 3 in zero. By comparison, 288 screws were placed in total in the freehand group, which were rated as grade A in 251, grade B in 28, grade C in eight, grade D in one, and no grade E in any screw. A total of 82 superior level facet joint screws were inserted in freehand group, which were marked as grade 0 in 62, grade one in 18, grade 2 in two, and grade 3 in zero. The robot-assisted technique was statistically superior to the freehand method in the accuracy of screw placement (P < 0.05). CONCLUSION: Compared with freehand screw implantation, in lumbar revision surgery, the Renaissance robot had higher accuracy and safety of pedicle screw implantation, fewer superior level facet joint violations, and less intra-operative blood loss and intra-operative fluoroscopy time.

Combined light- and heat-induced shape memory behavior of anthracene-based epoxy elastomers.

The development of multi-stimuli-responsive shape memory polymers has received increasing attention because of its scientific and technological significance. In this work, epoxy elastomers with reversible crosslinks are synthesized by polymerizing an anthracene-functionalized epoxy monomer, a diepoxy comonomer, and a dicarboxylic acid curing agent. The synthesized elastomers exhibit active responses to both light and heat enabled by the incorporated anthracene groups. When exposed to 365 nm UV light, additional crosslinking points are created by the photo-induced dimerization of pendant anthracene groups. The formation of the crosslinking points increases modulus and glass transition temperature of the elastomers, allowing for the fixation of a temporary shape at room temperature. The temporary shape remains stable until an external heat stimulus is applied to trigger the scission of the dimerized anthracene, which reduces the modulus and glass transition temperature and allows the elastomers to recover their original shapes. The effects of external stimuli on the thermal and dynamic mechanical properties of the elastomers are investigated experimentally and are correlated with molecular dynamics simulations that reveal the changes of structure and dynamics of the anthracene molecules and flexible chains.

Reliability and application of the new morphological classification system for chronic symptomatic osteoporotic thoracolumbar fracture.

BACKGROUND: We propose a new classification system for chronic symptomatic osteoporotic thoracolumbar fracture (CSOTF) based on fracture morphology. Research on CSOTF has increased in recent years; however, the lack of a standard classification system has resulted in inconvenient communication, research, and treatment. Previous CSOTF classification studies exhibit different symptoms, with none being widely accepted. METHODS: Imaging data of 368 patients with CSOTF treated at our hospital from January 2010 to June 2017 were systematically analyzed to develop a classification system. Imaging examinations included dynamic radiography, computed tomography scans, and magnetic resonance imaging. Ten investigators methodically studied the classification system grading in 40 cases on two occasions, examined 1 month apart. Kappa coefficients (κ) were calculated to determine intraobserver and interobserver reliability. Based on the radiographic characteristics, the patients were divided into 5 types, and different treatments were suggested for each type. Clinical outcome evaluation included using the visual analog score (VAS), the Oswestry disability index (ODI), and the American Spinal Injury Association (ASIA) impairment scale. RESULTS: The new classification system for CSOTF was divided into types I-V according to whether the CSOTF exhibited dynamic instability, spinal stenosis or kyphosis deformity. Intra- and interobserver reliability were excellent for all types (κ = 0.83 and 0.85, respectively). The VAS score and ODI of each type were significantly improved at the final follow-up compared with those before surgery. In all patients with neurological impairment, the ASIA grading after surgery was significantly improved compared with that before surgery (P < 0.001). CONCLUSIONS: The new classification system for CSOTF demonstrated excellent reliability in this initial assessment. The treatment algorithm based on the classification can result in satisfactory improvement of clinical efficacy for the patients of CSOFT.

Is laminectomy and fusion the better choice than laminoplasty for multilevel cervical myelopathy with signal changes on magnetic resonance imaging? A comparison of two posterior surgeries.

BACKGROUND: This study aimed to compare the clinical outcomes and complications between laminectomy and fusion (LF) and laminoplasty (LP) for multi-level cervical spondylotic myelopathy (MCSM) with increased signal intensity (ISI) on T2-weighted images (T2WI). METHODS: In this retrospective cohort study, we analyzed 52 patients with MCSM with ISI on T2WI who underwent laminoplasty (LP group). The Japanese Orthopedic Association (JOA) score, the Visual Analogue Scale (VAS) score, the physical and mental component scores (PCS and MCS) of Short-Form 36 (SF-36), and the extension and flexion ranges of motion (ROMs) were recorded. As controls, propensity score matching identified 52 patients who underwent laminectomy and fusion (LF group) from January 2014 to June 2016 using 7 independent variables (preoperation): age, sex, JOA score, SF-36 PCS, SF-36 MCS, preoperative symptom duration and high signal intensity ratio (HSIR). RESULTS: The operative duration in the LF group was significantly higher than that in the LP group. At the last follow-up, the JOA score, VAS score, and SF-36 (PCS and MCS) scores were all significantly improved in both groups. The extension and flexion ROMs were decreased in both groups but significantly better in the LP group than in the LF group. Both groups demonstrated similar clinical improvements at the final follow-up. The complication rate was higher in the LF group. CONCLUSION: The present study demonstrates that LP for MCSM with ISI on T2WI achieves similar clinical improvement as LF. However, longer operative durations, higher complication rates and lower extension and flexion ROMs were found in the LF group.

Can the Novel LumboIliac Triangle Technique Based on Biplane Oblique Fluoroscopy Facilitate Transforaminal Percutaneous Endoscopic Lumbar Discectomy for Patients with L5-S1 Disc Herniation Combined with High Iliac Crest? Case-Control Study of 100 Patients.

BACKGROUND: Percutaneous endoscopic lumbar discectomy (PELD) via the transforaminal approach is difficult at L5-S1 in patients presenting with high iliac crests (HIC). The conventional wisdom is that measurement using lumbar radiography, computed tomography (CT), or magnetic resonance imaging (MRI) is necessary. OBJECTIVES: The objective of this study was to introduce a lumbo-iliac triangular (LI-Tri) technique based on biplane oblique fluoroscopy and verify whether it facilitated transforaminal PELD for patients with L5-S1 lumbar disc herniation (LDH) combined with HIC. STUDY DESIGN: A retrospective analysis. SETTING: All data were from Honghui Hospital in Xi'an. METHODS: One hundred patients with L5-S1 LDH combined with HIC were treated with PELD. The LI-Tri technique was used in the first 50 patients (applied group). The other 50 patients were classified as the nonapplied group, in which the conventional technique was performed. Clinical outcome evaluation included Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) scores. The intervals of follow-up were scheduled at 1 day and 1, 3, 6, 12, and 24 months postoperatively. RESULTS: No significant difference was observed with respect to demographic information (P < .05, respectively). There were 8 patients in the nonapplied group with difficult punctures. Together with the remaining 50 patients, the puncture was successful with the LI-Tri technique. The mean operative duration was shorter in the applied group (55 vs 70 min, P < .01). Compared to the preoperative data, only the back pain VAS and ODI in the nonapplied group were nonsignificantly lower at one day postoperatively (P > .05, respectively). With the exception of the back pain VAS and ODI at one day postoperatively, no significant differences were observed in the 3 parameters at other time points postoperatively between 2 groups (P > .05, respectively). LIMITATIONS: The study is limited by its retrospective, nonrandomized controlled design. CONCLUSIONS: For patients with L5-S1 LDH combined with HIC treated by transforaminal PELD, the LI-Tri technique is simple and effective in preoperative evaluations, locating the skin entry point and guiding the puncture trajectory. Compared to the conventional technique, it shows advantages in terms of reducing intraoperative surgical duration and promoting fast postoperative recovery. KEY WORDS: Endoscopic discectomy, iliac crest, L5-S1 disc, PELD, percutaneous, transforaminal.

Epidemiological characteristics of spinal cord injury in Northwest China: a single hospital-based study.

BACKGROUND: While the cities in China in which spinal cord injury (SCI) studies have been conducted previously are at the forefront of medical care, northwest China is relatively underdeveloped economically, and the epidemiological characteristics of SCI have rarely been reported in this region. METHODS: The SCI epidemiological survey software developed was used to analyze the data of patients treated with SCI from 2014 to 2018. The sociodemographic characteristics of patients, including name, age, sex, and occupation, were recorded. The following medical record data, obtained from physical and radiographic examinations, were included in the study: data on the cause of injury, fracture location, associated injuries, and level of injury. Neurological function was evaluated using the American Spinal Injury Association (ASIA) impairment scale. In addition, the treatment and complications during hospitalization were documented. RESULTS: A total of 3487 patients with SCI with a mean age of 39.5 ± 11.2 years were identified in this study, and the male to female ratio was 2.57:1. The primary cause of SCI was falls (low falls 47.75%, high falls 37.31%), followed by traffic accidents (8.98%), and impact with falling objects (4.39%). Of all patients, 1786 patients (51.22%) had complications and other injuries. According to the ASIA impairment scale, the numbers of grade A, B, C, and D injuries were 747 (21.42%), 688 (19.73%), 618 (17.72%), and 1434 (41.12%), respectively. During the hospitalization period, a total of 1341 patients experienced complications, with a percentage of 38.46%. Among all complications, pulmonary infection was the most common (437, 32.59%), followed by hyponatremia (326, 24.31%), bedsores (219, 16.33%), urinary tract infection (168, 12.53%), deep venous thrombosis (157, 11.71%), and others (34, 2.53%). Notably, among 3487 patients with SCI, only 528 patients (15.14%) received long-term rehabilitation treatment. CONCLUSION: The incidence of SCI in northwest China was on the rise with higher proportion in males; fall and the MCVs were the primary causes of SCI. The occupations most threatened by SCI are farmers and workers. The investigation and analysis of the epidemiological characteristics of SCI in respiratory complications are important factors leading to death after SCI, especially when the SCI occurs in the cervical spinal cord. Finally, the significance of SCI rehabilitation should be addressed.

Cocktail Treatment with a Gelatin Sponge Impregnated with Ropivacaine, Dexamethasone, and Vitamin B12 Promotes Early Postoperative Recovery after Percutaneous Endoscopic Lumbar Discectomy: A Retrospective, Case-Controlled Study.

BACKGROUND: Percutaneous endoscopic lumbar discectomy (PELD) can only relieve mechanical compression but cannot directly reduce the inflammatory reaction of the adjacent nerve root, which contributes to persistent pain and physical disabilities postoperatively. Numerous studies have explored the application of epidural steroids after an open lumbar discectomy in relieving pain by reducing local inflammatory reactions and further peridural scar formation. OBJECTIVES: To explore that whether "cocktail treatment" in which a gelatin sponge was impregnated with ropivacaine, dexamethasone, and vitamin B12 promoted early postoperative recovery after PELD. STUDY DESIGN: Retrospective, case-controlled study. SETTING: All data were from Hong-Hui Hospital in Xi'an. METHODS: Between January 2016 and January 2017, 100 patients of single-level lumbar disc herniation were treated with PELD in our hospitals. The cocktail treatment was applied in the first 50 patients (group cocktail), and an equal size gelatin sponge without drugs was used in the other 50 patients as control (group noncocktail). The clinical outcome evaluation included the Visual Analog Scale (VAS) score for back and leg pain and Oswestry Disability Index (ODI) score. RESULTS: There was a significant difference in the mean periods of return to work (4.25 ± 1.88 weeks in the cocktail group and 5.18 ± 2.19 weeks in the noncocktail group) (P < 0.01). Compared with the preoperative data, a significant improvement in VAS scores of back pain and sciatica and ODI were observed in each follow-up interval (P < 0.05, respectively). In the noncocktail group, there were visible fluctuations in the 3 indicators within the first week after surgery. This phenomenon was not observed in the cocktail group, a difference that was statistically significant (P < 0.05, respectively). In further follow-up, no significant differences were observed between the 2 groups (P > 0.05, respectively). LIMITATIONS: The nonrandomized, single-center, retrospective design is a major limitation of this study. CONCLUSIONS: The "cocktail treatment" with a gelatin sponge impregnated with ropivacaine, dexamethasone, and vitamin B12 promotes early and satisfactory back and leg pain relief and fast functional recovery after PELD. KEY WORDS: Endoscopic lumbar discectomy, lumbar disc herniation, steroids, nerve root block, gelatin sponge.