Overcoming strength-ductility tradeoff with high pressure thermal treatment.

Conventional material processing approaches often achieve strengthening of materials at the cost of reduced ductility. Here, we show that high-pressure and high-temperature (HPHT) treatment can help overcome the strength-ductility trade-off in structural materials. We report an initially strong-yet-brittle eutectic high entropy alloy simultaneously doubling its strength to 1150 MPa and its tensile ductility to 36% after the HPHT treatment. Such strength-ductility synergy is attributed to the HPHT-induced formation of a hierarchically patterned microstructure with coherent interfaces, which promotes multiple deformation mechanisms, including dislocations, stacking faults, microbands and deformation twins, at multiple length scales. More importantly, the HPHT-induced microstructure helps relieve stress concentration at the interfaces, thereby arresting interfacial cracking commonly observed in traditional eutectic high entropy alloys. These findings suggest a new direction of research in employing HPHT techniques to help develop next generation structural materials.

Grain boundary plasticity initiated by excess volume.

Grain boundaries (GBs) serve not only as strong barriers to dislocation motion, but also as important carriers to accommodate plastic deformation in crystalline solids. During deformation, the inherent excess volume associated with loose atomic packing in GBs brings about a microscopic degree of freedom that can initiate GB plasticity, which is beyond the classic geometric description of GBs. However, identification of this atomistic process has long remained elusive due to its transient nature. Here, we use Au polycrystals to unveil a general and inherent route to initiating GB plasticity via a transient topological transition process triggered by the excess volume. This route underscores the general impact of a microscopic degree of freedom which is governed by a stress-triaxiality-based criterion. Our findings provide a missing perspective for developing a more comprehensive understanding of the role of GBs in plastic deformation.

Controllable Pseudoelasticity in Metallic Nanocrystals by Grain Boundary Engineering.

Materials with pseudoelasticity can recover from large strains exceeding their elastic limits during unloading, making them promising damage-tolerant building blocks for advanced nanodevices. Nevertheless, a practical approach to realize controllable pseudoelastic behavior at nanoscale remains challenging. Here, we proposed a grain boundary (GB) engineering approach to endow metallic nanocrystals with a controllable pseudoelasticity. Both in situ nanomechanical testing and atomistic simulations demonstrate that such controllable pseudoelasticity is governed by the extension and contraction of an inherent stacking fault array at the GB. By precisely tuning GB misorientation and inclination, our simulation results reveal that metallic nanocrystals can exhibit tailored pseudoelastic performance across a broad spectrum of GBs in different face-centered cubic metals. These findings enrich our understanding of the intrinsic pseudoelasticity of GBs and provide a GB engineering approach toward metallic materials with reversible deformability.

Asiaticoside ameliorates osteoarthritis progression through activation of Nrf2/HO-1 and inhibition of the NF-κB pathway.

Osteoarthritis has become the fourth cause of disability in the world and its occurrence and development are caused by apoptosis and extracellular matrix (ECM) degradation of chondrocytes. Asiaticoside (ASI) is a triterpene saponin compound obtained from Centella Asiatica and has anti-inflammatory and anti-apoptotic effects in various diseases. However, its effects on OA are not clear. In this study, we reported that ASI has a protective effect on the occurrence and progression of OA in vivo and in vitro, and demonstrated its potential molecular mechanism. In vitro, ASI treatment inhibited the release of pro-apoptotic factors induced by TBHP and promoted the release of the anti-apoptotic proteins. In addition, ASI promotes the expression of Aggrecan and Collagen II, while inhibiting the expression of thrombospondin motifs 5 (ADAMTS5) and matrix metalloproteinase-13 (MMP-13), which causes extracellular matrix (ECM) degradation. Mechanistically, ASI exerts its anti-apoptotic effect by activating the Nrf2/HO-1 pathway and preventing p65 from binding to DNA. Similarly, in vivo, ASI has been shown to have a protective effect in a mouse OA model. The conclusion is that our research shows that ASI can be used as a potential drug for the treatment of OA.

Hierarchical twinning governed by defective twin boundary in metallic materials.

Dense networks of deformation twins endow metals and alloys with unprecedented mechanical properties. However, the formation mechanism of these hierarchical twin structures remains under debate, especially their relations with the imperfect nature of twin boundaries (TBs). Here, we investigate the intrinsic deformability of defective TBs in face-centered cubic metallic materials, where the inherent kinks on a set of primary TBs are demonstrated to facilitate the formation of secondary and hierarchical nanotwins. This defect-driven hierarchical twinning propensity is critically dependent on the kink height, which proves to be generally applicable in a variety of metals and alloys with low stacking fault energies. As a geometric extreme, a fivefold twin can be constructed via this self-activated hierarchical twinning mechanism. These findings differ from the conventional twinning mechanisms, enriching our understanding of twinning-mediated plasticity in metallic materials.

Twinning-assisted dynamic adjustment of grain boundary mobility.

Grain boundary (GB) plasticity dominates the mechanical behaviours of nanocrystalline materials. Under mechanical loading, GB configuration and its local deformation geometry change dynamically with the deformation; the dynamic variation of GB deformability, however, remains largely elusive, especially regarding its relation with the frequently-observed GB-associated deformation twins in nanocrystalline materials. Attention here is focused on the GB dynamics in metallic nanocrystals, by means of well-designed in situ nanomechanical testing integrated with molecular dynamics simulations. GBs with low mobility are found to dynamically adjust their configurations and local deformation geometries via crystallographic twinning, which instantly changes the GB dynamics and enhances the GB mobility. This self-adjust twin-assisted GB dynamics is found common in a wide range of face-centred cubic nanocrystalline metals under different deformation conditions. These findings enrich our understanding of GB-mediated plasticity, especially the dynamic behaviour of GBs, and bear practical implication for developing high performance nanocrystalline materials through interface engineering.

Penta-Twin Destruction by Coordinated Twin Boundary Deformation.

Penta-twinned nanomaterials often exhibit unique mechanical properties. However, the intrinsic deformation behavior of penta-twins remains largely unclear, especially under the condition of high shear stress. In this study, we show that the deformation of penta-twins often subject to a structural destruction via dislocation-mediated coordinated twin boundary (TB) deformation, resulting in a reconstructed pentagon-shaped core. This reconstructed core region is mainly induced by the coordinated TB migration along different directions (for the nucleation and growth) and accelerated by the TB sliding (for the growth). The destructed penta-twin core can effectively accommodate the intrinsic disclination of the penta-twin, which further collapses beyond a critical size, as predicted by an energy-based criterion. These intrinsic deformation behaviors of penta-twins would enable the possibility of controlling the morphology of penta-twinned nanomaterials with unique properties.

Revealing extreme twin-boundary shear deformability in metallic nanocrystals.

Metals containing abundant coherent twin boundaries (TBs) are able to sustain substantial plastic deformation without fracture due to shear-induced TB migration and sliding. Retaining ductility in these metals, however, has proven difficult because detwinning rapidly exhausts TB migration mechanisms at large deformation, whereas TB sliding was only evidenced for loading on very specific crystallographic orientations. Here, we reveal the intrinsic shear deformability of twins in nanocrystals using in situ nanomechanical testing and multiscale simulations and report extreme shear deformability through TB sliding up to 364%. Sliding-induced plasticity is manifested for orientations that are generally predicted to favor detwinning and shown to depend critically on geometric inhomogeneities. Normal and shear coupling are further examined to delineate a TB orientation-dependent transition from TB sliding to TB cracking. These dynamic observations reveal unprecedented mechanical properties in nanocrystals, which hold implications for improving metal processing by severe plastic deformation.

Feasibility analysis of the use of anterior screw fixation in the treatment of pediatric odontoid fracture.

BACKGROUND: This study aimed to determine the feasibility of using anterior percutaneous screw fixation to treat odontoid fractures in children of different ages based on computed tomography (CT) measurements. METHODS: A total of 176 children were enrolled and divided into 3 groups: group A (<6 years of age; 18 males and 22 females), group B (6 to 12 years old; 40 males and 35 females), and group C (12 to 18 years old; 34 males and 27 females). Using 2-dimensional CT reconstruction technology, we measured the children's odontoid parameters, including the coronal external diameter of the base of the odontoid process, the sagittal external diameter of the base of the odontoid process, the length of the odontoid process, the height of the axis vertebral body, and the angle between the axial line of the odontoid process and the vertical line of the anterosuperior border of the C3 vertebral body. RESULTS: The mean coronal external diameter of the odontoid process base in children under 6 years old was 4.21±1.62 mm, which was not sufficient to accommodate a single screw. Among children aged 6 to 12 years old, this parameter varied widely, and the mean diameter was 5.50±2.80 mm. In the 12- to 18-year-old group, the diameter was 8.64±1.68 mm, which is similar to that of adults. The values of the total height of the axis, and the angle between the axial line of the and the vertical line of the anterosuperior C3 vertebral body border were lower than those for adults. CONCLUSIONS: The percutaneous odontoid screw fixation technique is not recommended for children under 6 years old. For children aged 6 to 18 years old, this technique is feasible, but individual differences must be considered preoperatively. Selecting the appropriate screw diameter, length, and angle according to the actual CT measurement result is critical.

Image measurements of os odontoideum in children.

BACKGROUND: Conservative therapy is used for children with odontoid fracture; however, when the odontoid fracture is complicated by significant displacement and unstable, surgery is required. Anterior cervical hollow lag screw fixation has been successfully used in adult patients, but until now, there has not been any relevant image measurement research in children with os odontoideum. The aim of the present study was to identify the morphometric changes of normal os odontoideum in children of different ages and to discuss parameters for screw fixation. METHODS: Computed tomography (CT) scanning data of normal os odontoideum in 120 children of different ages were measured. The parameters were as follows: transverse and vertical diameters of cancellous bone and cortical bone in os odontoideum basilar part, angle and distance from simulation screw insertion point (anterior mid-point of C2 vertebral body) to os odontoideum anterior angle as well as posterior angle, the optimal insertion angle, and the optimal screw length. RESULTS: The basilar part of normal os odontoideum was roughly round, and vertical diameter was slightly larger than transverse diameter. All parameters measured in the present study increased with age. The safety screw insertion angle range was 16-36°, and the optimal insertion angle ranged from 19° to 22°. The safety screw path length ranges in the 3-5-, 6-9-, and 10-14-year groups were 8-14, 10-16, and 12-21 mm, respectively, and the optimal screw length ranges were 13-14, 15-16, and 19-20 mm, respectively. The height of the axis showed a growing dimension followed by the advancing age in all groups. In each group, the height of the axis of the male is greater than the female. CONCLUSIONS: For children undergoing odontoid screw fixation for the treatment of type II odontoid fracture, it is important to select the appropriate screw diameter, length, and direction according to parameter changes of os odontoideum based on their age.

Apigenin Alleviates Intervertebral Disc Degeneration via Restoring Autophagy Flux in Nucleus Pulposus Cells.

Oxidative stress-induced apoptosis and senescence of nucleus pulposus (NP) cells play a crucial role in the progression of intervertebral disc degeneration (IVDD). Accumulation of studies has shown that activated autophagy and enhanced autophagic flux can alleviate IVDD. In this study, we explored the effects of apigenin on IVDD in vitro and in vivo. Apigenin was found to inhibit tert-butyl hydroperoxide (TBHP)-induced apoptosis, senescence, and ECM degradation in NP cells. In addition, apigenin treatment can restore the autophagic flux blockage caused by TBHP. Mechanistically, we found that TBHP may induce autophagosome and lysosome fusion interruption and lysosomal dysfunction, while apigenin alleviates these phenomena by promoting the nuclear translocation of TFEB via the AMPK/mTOR signaling pathway. Furthermore, apigenin also exerts a protective effect against the progression of IVDD in the puncture-induced rat model. Taken together, these findings indicate that apigenin protects NP cells against TBHP-induced apoptosis, senescence, and ECM degradation via restoration of autophagic flux in vitro, and it also ameliorates IVDD progression in rats in vivo, demonstrating its potential for serving as an effective therapeutic agent for IVDD.

Unilateral versus bilateral balloon kyphoplasty in treatment of osteoporotic vertebral compression fractures: A randomized controlled trial protocol.

BACKGROUND: It is currently controversial whether unilateral or bilateral balloon kyphoplasty (BKP) is superior in terms of postoperative outcomes in treatment of osteoporotic vertebral compression fracture (OVCF). In this context, the aim of this study was to prospectively evaluate and compare the radiographic and clinical outcomes of BKP using unilateral and bilateral approaches. METHODS: This was a randomized controlled study and was approved by the Severance Institutional Review Board in our hospital. The study protocol was designed in accordance with the Declaration of Helsinki guidelines. Patients who complained of chronic back pain secondary to OVCF, which occurred in thoracic lumbar region over 6 months and met the criteria of osteoporosis were the candidates for this procedure. A total of 150 patients were randomized to undergo either unilateral or bipedicular BKP. The outcomes measures inculded pain score, Oswestry Dysfunction Index, compression ratio, kyphotic angle, operation time, and postoperative complications. RESULTS: We were able to directly compare the outcomes of unilateral versus bilateral BKP and might reveal a better technique in OVCF. TRIAL REGISTRATION: this study protocol was registered in Research Registry (researchregistry5543).

Metallic nanocrystals with low angle grain boundary for controllable plastic reversibility.

Advanced nanodevices require reliable nanocomponents where mechanically-induced irreversible structural damage should be largely prevented. However, a practical methodology to improve the plastic reversibility of nanosized metals remains challenging. Here, we propose a grain boundary (GB) engineering protocol to realize controllable plastic reversibility in metallic nanocrystals. Both in situ nanomechanical testing and atomistic simulations demonstrate that custom-designed low-angle GBs with controlled misorientation can endow metallic bicrystals with endurable cyclic deformability via GB migration. Such fully reversible plasticity is predominantly governed by the conservative motion of Shockley partial dislocation pairs, which fundamentally suppress damage accumulation and preserve the structural stability. This reversible deformation is retained in a broad class of face-centred cubic metals with low stacking fault energies when tuning the GB structure, external geometry and loading conditions over a wide range. These findings shed light on practical advances in promoting cyclic deformability of metallic nanomaterials.

Baicalin augments the differentiation of osteoblasts via enhancement of microRNA-217.

Baicalin (BAI), a sort of flavonoid monomer, acquires from Scutellaria baicalensis Georgi, which was forcefully reported in diversified ailments due to the pleiotropic properties. But, the functions of BAI in osteoblast differentiation have not been addressed. The intentions of this study are to attest the influences of BAI in the differentiation of osteoblasts. MC3T3-E1 cells or rat primary osteoblasts were exposed to BAI, and then cell viability, ALP activity, mineralization process, and Runx2 and Ocn expression were appraised through implementing CCK-8, p-nitrophenyl phosphate (pNPP), Alizarin red staining, western blot, and RT-qPCR assays. The microRNA-217 (miR-217) expression was evaluated in MC3T3-E1 cells or rat primary osteoblasts after BAI disposition; meanwhile, the functions of miR-217 in BAI-administrated MC3T3-E1 cells were estimated after miR-217 inhibitor transfection. The impacts of BAI and miR-217 inhibition on Wnt/ß-catenin and MEK/ERK pathways were probed to verify the involvements in BAI-regulated the differentiation of osteoblasts. BAI accelerated cell viability, osteoblast activity, and Runx2 and Ocn expression in MC3T3-E1 cells or rat primary osteoblasts, and the phenomena were mediated via activations of Wnt/ß-catenin and MEK/ERK pathways. Elevation of miR-217 was observed in BAI-disposed MC3T3-E1 cells or rat primary osteoblasts, and miR-217 repression annulled the functions of BAI in MC3T3-E1 cell viability and differentiation. Additionally, the activations of Wnt/ß-catenin and MEK/ERK pathways evoked by BAI were both restrained by repression of miR-217. These explorations uncovered that BAI augmented the differentiation of osteoblasts via activations of Wnt/ß-catenin and MEK/ERK pathways by ascending miR-217 expression.

Vitexin alleviates ER-stress-activated apoptosis and the related inflammation in chondrocytes and inhibits the degeneration of cartilage in rats.

Excessive extracellular matrix degradation and chondrocyte apoptosis are the pathological features of osteoarthritis (OA). The ability of flavonoid compounds isolated from Chinese hawthorn leaves to exert protective effects on several diseases, via inhibition of oxidative stress and inflammation, has been demonstrated in several studies. This study explored the effects of vitexin on chondrocytes, and the underlying mechanisms thereof. Vitexin, an active ingredient in hawthorn leaf extracts, was shown to exert protective effects on chondrocytes, by inhibiting the expression of GRP78 and PDI, and an apoptotic protein (CHOP) induced by interleukin-1ß. It also modulated thapsigargin-induced upregulation of GRP78 and PDI and subsequently an apoptotic protein (CHOP). Among rat chondrocytes, both the ER stress-activated nuclear factor kappa B (NF-κB) pathway and the induced expression of inflammatory cytokines (IL-6 and TNF-α) were significantly inhibited by vitexin. Finally, vitexin attenuated the progression of OA in vivo in rats. Taken together, all data demonstrate the relationship of ER stress and inflammation in the progression of OA, the ability of vitexin to protect chondrocytes and thus its therapeutic potential in patients with OA.

Risk Factor of Failed Reduction of Posterior Ligamentatoxis Reduction Instrumentation in Managing Thoracolumbar Burst Fractures: A Retrospective Study.

OBJECTIVE: To determine whether radiographic findings associated with thoracolumbar burst fractures could be predictors of failure of short-segment posterior instrumentation with insertion screw at the fracture level (SSPI-f). METHODS: Seventy-five patients with thoracolumbar burst fracture surgically treated by SSPI-f were enrolled in the study and divided into 2 groups: a reduction group (n = 46) and a failed-reduction group (n = 29). Radiographic data including local kyphosis, Cobb angle, anterior vertebral height, posterior vertebral height (PVH), anterior/posterior vertebral height ratio, interpedicle distance (IPD), bony compress area, bony fracture area, and compress-fracture area of the fractured vertebra and clinical data including age and neurologic function were also analyzed. t test, Pearson χ2 test, and binary logistic regression were performed to compare the values. RESULTS: The PVH in the failed-reduction group was smaller than that of the reduction group (83.5% ± 7.2% and 89.1% ± 5.4%, respectively) (P = 0.001). The IPD differed between the reduction and failed-reduction group (18.0% ± 4.1% and 25.8% ± 7.1%, respectively) (P < 0.001). There was a statistical difference between the 2 groups in delayed time before surgery (P = 0.008). There was a significant difference of bony fracture area and compress-fracture area of the fractured vertebra between the failed-reduction and reduction group (both P < 0.001). Binary logistic regression showed that IPD was a risk factor of reduction failure of SSPI-f (P = 0.001). CONCLUSIONS: These results showed that increased IPD was a risk factor of failed-reduction of SSPI-f in managing thoracolumbar burst fractures, particularly for patients with neurologic deficit, whereas local kyphosis, Cobb angle, anterior vertebral height, PVH, anterior/posterior vertebral height ratio, bony compress area, bony fracture area, and compress-fracture area of the fractured vertebra were not.

Comparison of minimally invasive and open transforaminal lumbar interbody fusion in the treatment of single segmental lumbar spondylolisthesis: minimum two-year follow up.

BACKGROUND: Compare the efficacy and safety of minimally invasive and open transforaminal lumbar interbody fusion (TLIF) in the treatment of single segmental lumbar spondylolisthesis. METHODS: From 2010-01 to 2015-10, in total, 167 patients with single segmental spondylolisthesis treated by TLIF were included, 79 cases in minimally invasive TLIF (MI-TLIF) group and 88 cases in open TLIF group. The peri-operative parameters of operative time, estimated blood loss and length of postoperative hospital stay was recorded, as well as complications. Visual Analogue Scale (VAS) of low back pain and leg pain, and Oswestry Disability Index (ODI) were used to assess the pain and functional outcomes at pre-operatively, 3 months/1 year/2 years/5 years after operation. The radiographic parameters of posterior height of the intervertebral space and segmental lordosis were measured too. RESULTS: No significantly difference was found at baseline characteristic data of age, gender ratio, the percentage of degenerative and isthmic spondylolisthesis, the percentage of slip, and segmental distribution between MI-TLIF and open TLIF groups. MI-TLIF group had less estimated intra-operative blood loss (163.7±49.6 mL) than open TLIF group (243.3±70.2 mL, P<0.001) and had shorter post-operative hospital stay (5.8±1.4 days) than open TLIF group (7.3±2.9 days, P<0.001). Both MI-TLIF and open TLIF can significantly reduce the VAS of low back pain, VAS of leg pain, ODI, and improve the posterior height of the intervertebral space and segmental lordosis, but no significantly difference was found of them between two groups. CONCLUSIONS: Our study suggests that MI-TLIF is a safe and effective choice in the treatment of lower grade lumbar spondylolisthesis (grade II or less), and it has advantages of less blood loss, postoperative hospital stay when compared to open TLIF.

The outcomes of percutaneous kyphoplasty in treatment of the secondary osteoporotic vertebral compression factures: a case-control study.

BACKGROUND: To investigate the outcomes of using percutaneous kyphoplasty in the treatment of the secondary osteoporotic vertebral compression fractures. METHODS: Eighty-one patients had the secondary single segmental osteoporotic vertebral compression fractures after the initial fractures and treated by percutaneous kyphoplasty were reviewed, 74 of them had minimum 2 years follow-up were included in this study. The 74 patients with primary osteoporotic vertebral compression fractures treated by percutaneous kyphoplasty at the same time period were matched as control group in 1:1 ratio. Visual Analogue Scales (VAS) and Oswestry Disability Index (ODI) were used to assess the back pain and functional outcomes. The kyphotic angulation (KA) and compression ratio (CR) of the fractured vertebra was measured too. RESULTS: Both the secondary fracture group and control group had significantly relieved back pain, improved functional outcomes, corrected KA and restored CR after operation, but no difference was found between two groups. CONCLUSIONS: Our findings suggest that percutaneous kyphoplasty is an effective and safe procedure for patients with secondary single segmental osteoporotic vertebral compression fractures; it can achieve similar clinical outcomes to the primary osteoporotic vertebral compression fractures.

Transmuscular Ultrasonography of the Placement of Thoracolumbar Pedicle Screws: A Cadaveric Study.

BACKGROUND: Transpedicular screw fixation has a biomechanical advantage of improving fusion rates. In posterior thoracolumbar immobilization, a large number of screws cause perforation to the pedicle or vertebral body. Radiography and computed tomography (CT) have been used to minimize this complication. The ability of ultrasound (US) to detect the pedicle breach during placement of the screw is unknown. The aim of this study was to evaluate the sensitivity of US for detecting breaches. METHODS: A B-type transducer was used to scan 216 titanium pins inserted into cadaveric pedicles. Of the pins, 180 were intentionally misplaced: 90 pins breached the lateral wall of the pedicle, and 90 pins pierced the anterior wall of the vertebral body. US images were reviewed by 3 examiners blinded to both the procedure and the corresponding CT findings. The perforation length of pins was measured by 3 radiologists on CT images. RESULTS: CT data were divided into 2 groups. In group 1 (perforation length 0-2 mm), sensitivity of US for detecting lateral wall and anterior wall perforation was 80.95% and 76.42%, respectively; in group 2 (perforation length 2-4 mm), sensitivity was 94.79% and 91.93%. Overall sensitivity of US to detect lateral wall and anterior wall perforation was 89.63% and 86.30%, respectively. The sensitivity of US for detecting perforation was greater in the lateral wall than in the anterior wall. Sensitivity of US was greater in group 2 than group 1 for both lateral and anterior perforation. CONCLUSIONS: US can be applied to detect perforation of ≤4 mm. Use of US may improve patient safety.