Identification of disulfidptosis-related clusters and construction of a disulfidptosis-related gene prognostic signature in triple-negative breast cancer.

Objective: This study aimed to explore disulfidptosis-related clusters of triple-negative breast cancer (TNBC) and build a reliable disulfidptosis-related gene signature for forecasting TNBC prognosis. Methods: The disulfidptosis-related clusters of TNBC were identified based on public datasets, and a comparative analysis was conducted to assess their differences in the overall survival (OS) and immune cell infiltration. Morever, the differentially expressed genes (DEGs) between clusters were recognized. Then, the prognostic DEGs were then chosen. A prognostic signature was constructed by the prognostic DEGs, followed by nomogram construction, drug sensitivity, immune correlation, immunotherapy response prediction, and cluster association analyses. Results: Two disulfidptosis-related clusters of TNBC were identified, which had different OS and macrophage infiltration. Moreover, 235 DEGs were identified between two clusters. A prognostic signature was then constructed by five prognostic DEGs including HLA-DQA2, CCL13, GBP1, LAMP3, and SLC7A11. This signature was highly valuable in predicting prognosis. A nomogram was built by risk score and AJCC stage, which could forecast OS accurately. Moreover, patients with high-risk scores exhibited greater sensitivity to chemotherapy drugs such as lapatinib and had a lower immunotherapy response. Conclusions: Two TNBC clusters linked to disulfidptosis were identified, with different OS and immune cell infiltration. Moreover, a five-disulfidptosis-related gene signature may be a powerful prognostic biomarker for TNBC.

Biomechanical investigation of a customized interspinous spacer system in the treatment of degenerative disc diseases: A finite element analysis.

BACKGROUND: A novel interspinous fixation system based on anatomical parameters and incorporating transfacetopedicular screws, was developed to treat degenerative disc diseases. The biomechanical characteristics of the novel system were evaluated using finite element analysis in comparison to other classical interspinous spacers. METHODS: The L1-S1 lumbar spine finite element models were surgically implanted with the novel system, Coflex and DIAM devices at the L4/L5 segment to assess the range of motion, the pression distribution of intervertebral disc, the peak stresses on the spinous process and implant during various motions. FINDINGS: Range of motions of the L4/L5 surgical segment were reduced by 29.13%, 61.27%, 77.35%, 33.33%, and the peak stresses of intervertebral disc were decreased by 36.82%, 67.31%, 73.00%, 69.57% for the novel system in flexion, extension, lateral bending, and axial rotation when compared with the Coflex, and they were declined by 34.53%, 57.86%, 75.81%, 25.21%; 36.22%, 67.31%, 75.01%, 71.40% compared with DIAM. The maximum stresses of the spinous process were 29.93 MPa, 24.66 MPa, 14.45 MPa, 24.37 MPa in the novel system, and those of Coflex and DIAM were 165.3 MPa, 109 MPa, 84.79 MPa, 47.66 MPa and 52.59 MPa, 48.78 MPa, 50.27 MPa, 44.16 MPa during the same condition. INTERPRETATION: Compared to other interspinous spacer devices, the novel interspinous fixation system demonstrated excellent stability, effectively distributing load on the intervertebral disc, and reducing the risk of spinous process fractures. The personalized design of the novel interspinous fixation system could be a viable option for treating degenerative disc diseases.

Biomechanical effects of osteoporosis severity on the occurrence of proximal junctional kyphosis following long-segment posterior thoracolumbar fusion.

BACKGROUND: Proximal junctional kyphosis is a common long-term complication in adult spinal deformity surgery that involves long-segment posterior spinal fusion. However, the underlying biomechanical mechanisms of the impact of osteoporosis on proximal junctional kyphosis remain unclear. The present study was to evaluate adjacent segment degeneration and spine mechanical instability in osteoporotic patients who underwent long-segment posterior thoracolumbar fusion. METHODS: Finite element models of the thoracolumbar spine T1-L5 with posterior long-segment T8-L5 fusion under different degrees of osteoporosis were constructed to analyze intervertebral disc stress characterization, vertebrae mechanical transfer, and pedicle screw system loads during various motions. FINDINGS: Compared with normal bone mass, the maximum von Mises stresses of T7 and T8 were increased by 20.32%, 22.38%, 44.69%, 4.49% and 29.48%, 17.84%, 40.95%, 3.20% during flexion, extension, lateral bending, and axial rotation in the mild osteoporosis model, and by 21.21%, 18.32%, 88.28%, 2.94% and 37.76%, 15.09%, 61.47%, -0.04% in severe osteoporosis model. The peak stresses among T6/T7, T7/T8, and T8/T9 discs were 14.77 MPa, 11.55 MPa, and 2.39 MPa under lateral bending conditions for the severe osteoporosis model, respectively. As the severity of osteoporosis increased, stress levels on SCR8 and SCR9 intensified during various movements. INTERPRETATION: Osteoporosis had an adverse effect on proximal junctional kyphosis. The stress levels in cortical bone, intervertebral discs and screws were increased with bone mass loss, which can easily lead to intervertebral disc degeneration, bone destruction as well as screw pullout. These factors have significantly affected or accelerated the occurrence of proximal junctional kyphosis.

Biomechanical study of cornea response under orthokeratology lens therapy: A finite element analysis.

Orthokeratology (OK) is becoming a mainstream modality for myopia correction and control, but its underlying mechanism is not yet fully understood. In this study, the biomechanical response of cornea under the OK lens was investigated to further understand the mechanism of OK therapy. Numerical models of the cornea and OK lens with different corneal refractive powers and myopia degrees were established to analyze features and differences of the spatial displacement and stress distribution in different areas of the anterior corneal surface by finite element method. Displacement distributions on the anterior cornea surface with refractive powers of 39.5, 43, 46 D, and myopia degrees of -1.0, -3.0, -6.0 D demonstrate similar deformation trends and nearly rotationally symmetrical attributes of different corneal parameters. Displacement of mid-peripheral cornea was significantly high compared with that of the central and peripheral cornea, peaking at ~2.4 mm off the corneal apex. The stress increased with the increase in myopia degrees and was significantly large for the myopia degrees of -6.0 D at S1; the stress at S2 and S6 was low and stable and did not differ much at S3; the stress at S4 and S5, however, was extremely high. In summary, simulation result of orthokeratology can effectively evaluate the performance of OK lens and it properly associates with the differential map of the corneal topography. The base curve of the OK lens may also play a role in mid-peripheral corneal steepening. The design around the OK lens' alignment curve needs to be optimized.

Biomechanical analysis of a customized lumbar interspinous spacer based on transfacetopedicular screw fixation: A finite element study.

The interspinous spacer (ISP) is a minimally invasive surgical device implanted into the interspinal space to treat lumbar degenerative diseases. Unfortunately, ISPs sometimes cause device breakage and spinal process fracture. Our aim was to elaborate the design of lumbar customized posterior fixation system (CISP system), encompassing a customized ISP body and transfacetopedicular screws, and examine its biomechanical effect on the lumbar spine using finite element (FE) analysis. We constructed the CISP system, based on the interspinal anatomical data at the surgical level. We generated the L3-S1 FE models, implanted with the polyetheretherketone (PEEK) CISP system, titanium alloy (TI) CISP system, and Coflex device at the L4/L5 segment, and determined the lumbar segmental range of motions (ROMs), intervertebral discs (IVD) peak stress, and implant stresses. The CISP system enhanced mobility restriction at the surgical level, compared to the Coflex device. Furthermore, the IVD peak stress reduction was more obvious in the CISP system than the Coflex device, particularly during extension. Under the same motion mode, the maximum stress on the TI CISP system was smaller than on the Coflex device, but larger than the PEEK CISP system. Given these evidences, PEEK appeared to be a better material for the CISP body.

The design of a novel arthroscopy shaver.

Cases of arthroscopic surgery have increased over the past two decades, and arthroscopic shaver systems have become a commonly used orthopedic tool. Nevertheless, most shavers generally have problems such as the cutting edge is not sharp enough and easy to wear. This paper aims to discuss the structural characteristics of BJKMC's (Bojin◊ Kinetic Medical) novel arthroscopic shaver, the double serrated blade. The product's design and verification process are outlined. BJKMC's articular arthroscopy shaver has a "tube in a tube" structure, comprising a stainless steel outer sleeve and a rotating hollow inner tube. The outer sleeve and inner tube have corresponding suction and cutting windows, and there are serrated teeth on the inner and outer casing. To verify the design rationality, it was compared to Dyonics◊'s equivalent product, the Incisor◊ Plus Blade. The appearance, cutting tool hardness, metal pipe roughness, cutting tool wall thickness, tooth profile, and angle, overall structure, and the key dimensions were examined and compared. Compared with Dyonics◊'s Incisor◊ Plus Blade, BJKMC's Double Serrated Blade had a smoother working surface, harder and thinner blade head. Therefore, BJKMC's product may have satisfactory performance when it comes to surgery.

Biomechanical investigation of intra-articular cage and cantilever technique in the treatment of congenital basilar invagination combined with atlantoaxial dislocation: a finite element analysis.

Biomechanical effect of posterior intra-articular cages and cantilever technique on the congenital basilar invagination (BI) combined with atlantoaxial dislocation (AAD) was investigated and evaluated using finite element (FE) analysis. A 3D nonlinear occipitocervical segment C0-C3 FE models of congenital BI and AAD was established. Then, the FE model treated with C2 pedicle screw and occipital plate fixation coupled with intra-articular cages (Cage + C2PS + OP) was compared to that without intra-articular cages (C2PS + OP). The range of motion (ROM) of C0C1-C2 and the maximum von Mises stresses (MVMS) on the intra-articular cages, screw-plate system, and C2 endplate were calculated and compared to further analyze the stability of atlantoaxial joint and assess the collapse and fracture risks of intra-articular cages and screw-plate system. ROM of C0C1-C2 segment was reduced by 57.58%, 63.33%, 78.18%, and 75.90%, and the peak stresses of C2 pedicle screw and occipital plate were decreased by 84.86%, 72.90%, 73.24%, and 84.90% and 78.35%, 76.64%, 81.82%, and 89.49% for Cage + C2PS + OP model in flexion, extension, lateral bending, and axial rotation when compared with the C2PS + OP model under the same condition. The MVMS of intra-articular cages were 13.80 MPa, 40.26 MPa, 26.93 MPa, and 17.50 MPa and those of C2 endplate were 14.56 MPa, 34.80 MPa, 36.29 MPa, and 37.56 MPa in Cage + C2PS + OP model under same conditions. Posterior intra-articular cages and cantilever technique to treat BI-AAD can improve the stability of the atlantoaxial joint and reduce the risk of screw-plate breakage. The intra-articular cages can not only complement the height loss on account of atlantooccipital fusion but also provide stable support for posterior fixation fusion.

Biomechanical evaluation of combined proximal tibial osteotomy for varus knee osteoarthritis implanted novel designed plate system: Finite element analysis.

BACKGROUND: Combined proximal tibial osteotomy (CPTO) is an innovative and effective procedure for correcting varus knee osteoarthritis (VKOA) with intra- and extra-articular deformity. Here, we designed a novel internal fixation plate system for CPTO and assessed the biomechanical strength of the bone-implant. METHODS: Our newly designed CPTO internal fixation plate system included a specialized plate shape, combination holes, locking screw holes, screw position, and size of fixation. The biomechanical performance of this plate system in CPTO treatment was compared via finite element analysis (FEA) to traditional Tomofix devices implanted in the opening-wedge high tibial osteotomy (OWHTO), tibial condylar valgus osteotomy (TCVO), and CPTO. RESULTS: The tibial wedge stiffness and displacement after CPTO implantation of the novel internal plate fixation increased by 9.6%, which was -65% higher than the CPTO with the Tomofix system. The average stress of the bone, plate, and screws in the CPTO implanted the novel designed plate system compared to the Tomofix system decreased by 12.7%, 1.9%, and 20.3 %, respectively. The device maximum stress and wedge stiffness after CPTO with the novel plate system versus traditional OWHTO and TCVO with the Tomofix system were 255.7 MPa, 204 MPa, 130.4 MPa, and 678.9 N/mm, 660.3 N/mm, 1626.0 N/mm, respectively. CONCLUSIONS: The novel internal fixation plate system usage during CPTO exhibited similar bone-implant biomechanical strength, compared to OWHTO, but with enhanced construct stability.

A biomechanical study of ligament tethers strengthening for the prevention of proximal junctional kyphosis after posterior long-segment spinal fusion.

BACKGROUND: Proximal junctional kyphosis is a known complication of posterior long-segment thoracolumbar fusion. Here, the biomechanical effectiveness of ligament tethers strengthening and vertebral body augmentation, in proximal junctional kyphosis prevention was explored using the finite element analysis. METHODS: Based on a validated model of T1-L5 with the pedicle screw system instrumented T8-L5, strengthening models with different strategies were created to assess the range of motion in proximal vertebrae, vertebrae stress, pedicle screw stress, and pressure on intervertebral discs during extension, flexion, lateral bending, and axial rotation motions. Strengthening strategies included two- and three-level posterior ligament tethers (TE-T7-T9 and TE-T6-T9), and tethers with T7 &T8 vertebral body augmentation (TECE-T7-T9 and TECE-T6-T9). FINDINGS: Compared to the spinal fusion model, the ligament tethers strengthening significantly reduced the flexion-extension range of motion difference among the proximal vertebrae. During the flexion-extension motion, the T8 vertebra stresses in the TE-T7-T9, TE-T6-T9, TECE-T7-T9, and TECE-T6-T9 models were distinctively reduced, the values decreased by 26.8%, 28.3%, 28.8%, and 9.6%, respectively, during flexion, and by 21.9%, 35.2%, 23%, and 18.6%, respectively, during extension. In the strengthening models, the maximum stresses on the T7/T8 intervertebral disc in the TE-T6-T9 model were reduced by 13.8% during flexion and by 14.7% during extension. INTERPRETATION: Based on our results, the ligament strengthening configuration of the three-level posterior tethers produced a more gradual transition in range of motion, vertebrae stresses, and intervertebral discs stress between the fused and non-fused segments, especially during flexion-extension, which may significantly decrease the proximal junctional kyphosis biomechanical risk.

A biomechanical study of proximal junctional kyphosis after posterior long segment fusion with vertebral body augmentation.

Background Proximal junction kyphosis is a common clinical complication of posterior long-segment spinal fusion and vertebral body augmentation method is one of the effective approaches to prevent it. The purpose of this study was to explore the biomechanical effect of proximal junction kyphosis after posterior long-segment thoracolumbar fusion with different vertebral augmentation schemes using finite element analysis. Methods 3D nonlinear finite element models of T1-L5 spine posterior long-segment T8-L5 thoracolumbar fusion combined with T7, T8 and T7&T8 vertebral bone cement augmentation were constructed from human spine CT data and clinical surgical operation scheme to analyze the von Mises stress in the vertebrae, intervertebral discs pressure and pedicle screws system loads under the flexion, extension, lateral bending and axial rotation motion. Findings Compared with thoracolumbar posterior long-segment fusion model, T7 maximum stress in T7, T8 and T7&T8 vertebrae augmentation models were reduced by 8.64%, 7.17%, 8.51%;0.79%, -3.88%,1.67%;4.02%, 5.30%, 4.27% and 3.18%, 3.06%, -6.38% under the flexion, extension, lateral bending and axial rotation motion. T7/T8 intervertebral disc pressure in T7, T8, T7&T8 vertebral augmentation models were 36.71Mpa,29.78Mpa,36.47Mpa;22.25Mpa,18.35Mpa,22.06Mpa;84.27Mpa,68.17Mpa, 83.89Mpa and 52.23Mpa, 38.78Mpa,52.10Mpa under the same condition. The maximum stress 178.2Mpa of pedicle screws is mainly distributed at the root of screw. Interpretation Thoracolumbar posterior long-segment fusion with proximal double-segment vertebral augmentation should be recommended to prevent proximal junction kyphosis than single-segment augmentation. Simulation results can provide theoretical foundations and assist surgeons in selecting the appropriate operation scheme.

A ten N6-methyladenosine-related long non-coding RNAs signature predicts prognosis of triple-negative breast cancer.

BACKGROUND: Patients with triple-negative breast cancer (TNBC) face a major challenge of the poor prognosis, and N6-methyladenosine-(m6A) mediated regulation in cancer has been proposed. Therefore, this study aimed to explore the prognostic roles of m6A-related long non-coding RNAs (LncRNAs) in TNBC. METHODS: Clinical information and expression data of TNBC samples were collected from TCGA and GEO databases. Pearson correlation, univariate, and multivariate Cox regression analysis were employed to identify independent prognostic m6A-related LncRNAs to construct the prognostic score (PS) risk model. Receiver operating characteristic (ROC) curve was used to evaluate the performance of PS risk model. A competing endogenous RNA (ceRNA) network was established for the functional analysis on targeted mRNAs. RESULTS: We identified 10 independent prognostic m6A-related LncRNAs (SAMD12-AS1, BVES-AS1, LINC00593, MIR205HG, LINC00571, ANKRD10-IT1, CIRBP-AS1, SUCLG2-AS1, BLACAT1, and HOXB-AS1) and established a PS risk model accordingly. Relevant results suggested that TNBC patients with lower PS had better overall survival status, and ROC curves proved that the PS model had better prognostic abilities with the AUC of 0.997 and 0.864 in TCGA and GSE76250 datasets, respectively. Recurrence and PS model status were defined as independent prognostic factors of TNBC. These ten LncRNAs were all differentially expressed in high-risk TNBC compared with controls. The ceRNA network revealed the regulatory axes for nine key LncRNAs, and mRNAs in the network were identified to function in pathways of cell communication, signaling transduction and cancer. CONCLUSION: Our findings proposed a ten-m6A-related LncRNAs as potential biomarkers to predict the prognostic risk of TNBC.

Three-Dimensional Finite Element Analysis of the Effects of Ligaments on Human Sacroiliac Joint and Pelvis in Two Different Positions.

To present the ligament effects on sacroiliac joint (SIJ) stability and human pelvis biomechanical characteristics in two different positions by using three-dimensional (3D) finite element (FE) models of pelvis. Based on the computed tomography (CT) data of human pelvis, three-dimensional FE models of human pelvis in sitting and standing positions were established, which include the bone (sacrum, ilium, and coccyx) and six ligaments (sacroiliac, sacrospinous, sacrotuberous, inguinal, superior pubic, and arcuate pubic ligaments). 600 N vertical load was applied at the upper surface of sacrum to analyze the stress and displacement distribution of pelvis and SIJ. The simulation results demonstrated that the maximum stresses of sacrum and ilium on SIJ contact surface were 5.63 MPa and 7.40 MPa in standing position and 7.44 MPa and 7.95 MPa in sitting position. The stresses of ligament dysfunction group were higher than that of health group, which increased by 22.6% and 35.7% in standing position and 25.2% and 43.6% in sitting position in sacrum and ilium. The maximum displacements located on the upper surface of sacrum, which were 0.13 mm and 1.04 mm in standing and sitting positions. Ligaments dysfunction group increased 30.7% and 9.6% than health group in standing and sitting positions. The integral displacement of pelvis was greater in sitting position. The location of stress concentration and displacement distribution of pelvic bone are closely resembled previous research results in two different positions. The simulation results may provide beneficial information and theoretical models for clinical research of pelvic fracture, joint movement, and ligament functional injuries, and so on.

Assessment of arthroscopic shavers: a comparison test of resection performance and quality.

BACKGROUND: Arthroscopic shavers play an indispensable role in arthroscopic debridement. They have exquisite structures and similar designs. The purpose of this study was to establish a reproducible testing protocol to compare the resection performance and the quality (tensile strength, torsional strength, and corrosion resistance) of different arthroscopic shavers with comparable designs. We hypothesized that there could be little difference in resection performance and quality between these shavers. METHODS: Incisor Plus Blade (IPB; Smith & Nephew, Andover, MA) and Double Serrated Plus Blade (DSPB; BJKMC, Shanghai, China) were selected for resection performance and quality test. For resection performance testing, the resection torque, which is the minimum torque required to cut off silicone blocks with the same cross-sectional area, was measured to evaluate the resection performance of shaver blades when the other factors remain the same. For quality testing, tensile and torsion tests of the shavers' joint part were performed, and ultimate failure load and maximum torque were measured and compared. The corrosion resistance of these blades was assessed by the boiling water test based on the ISO13402. RESULTS: No significant difference existed in the resection torque between the shaver blades of IPB and DSPB (P = 0.54). To the failure load of shavers' joint parts, IPB was significantly higher than DSPB, both in the outer and inner blades (P < 0.0001). The maximum torque of the joint part had no significant difference between IPB and DSPB (for inner blades P = 0.60 and outer blades P = 0.94). The failure load (for both IPB and DSPB P < 0.0001) and maximum torque (for IPB P = 0.0475 and DSPB P = 0.015) of the inner blades were higher than those of the outer blades. No blemishes were observed on the surface of the blades after corrosion resistance tests. CONCLUSIONS: This study provided some new methods to evaluate the resection performance and quality of different shavers. The resection performance, the torsional strength of the joint part, and the corrosion resistance of IPB and DSPB may show comparable properties, whereas the tensile strength of the shavers' joint part showed some level of difference.

[Reconstruction of the Three-dimensional Model of Cervical Vertebrae Segments Based on CT Image and 3D Printing].

OBJECTIVE: Reconstruct the three-dimensional model of cervical vertebrae segments based on CT image and print it with 3D techniques to provide the clinical diagnosis with clear and specific models of pathological changes and conduct simulated surgery to improve operation's effect. METHODS: We imported the sequential geological data of human cervical vertebrae which is based on CT image into MIMICS software to achieve the segmentation picture of C4~C7 segments of cervical vertebrae. Then, after constructing the tentative 3D model, we put the data into GEOMAGIC Studio to get the digital model for 3D printing. RESULTS: By using the two reverse engineer software MIMICS and GEOMGIC Studio, we got the clear, accurate and specific 3D model of the C4~C7 segments of cervical vertebrae with complex and irregular anatomic structure. Thus, this will provide a powerful reference for the research on the case of lesion. CONCLUSIONS: The complete and clear 3D models of the cervical vertebrae we achieved could provide a new tool for research on the case of lesion and cervical spine bio-mechanics.

Molecular mechanism of activated T cells in breast cancer.

INTRODUCTION: This study aimed to explore the effect of activated T cells on breast cancer (BC) cells and provide a theoretical basis for the interaction mechanism studies between BC and immune cells. METHODS: The microarray dataset GSE73527 was downloaded from the Gene Expression Omnibus database. The common differentially expressed mRNAs (co-DEMs) and the common differentially expressed long non-coding RNAs (co-DElncRNAs) were identified between MDA-MB-231 cells and MCF7 activated human T cells, respectively. The RNA-miRNA-lncRNA (ceRNA) network was constructed. Furthermore, the Kyoto encyclopedia of genes and genomes pathway and the gene ontology function analyses were performed on co-DEMs. The protein-protein interaction networks and modules were investigated. RESULTS: A total of 639 co-DEMs (such as interleukin-6 [IL6] and signal transducer and activator of transcription 1 [STAT1]) were detected in this study. Defense response to other organisms and herpes simplex infection were the most outstanding function and pathway assembled with co-DEMs, respectively. One protein-protein interaction network and three modules were further constructed. A total of 88 mRNA-miRNA-lncRNA relationships such as BTN3A1-has-mir-20-b-5p-HCP5 were explored in the ceRNA network. CONCLUSION: Activated T cells may play a crucial role in the defense response to other organism functions and herpes simplex infection pathways by upregulating IL6 and STAT1, which further affected the progression of BC. The BTN3A1-has-miR-20b-5p-HCP5 relationship may be the potential interaction mechanism between BC and immune cells.

[Finite Element Analysis of Biomechanics of Cervical Spine after Dynamic Cervical Implant Surgery].

This study aims to investigate the range of motion(ROM)and the stress variation in the intervertebral disc and the vertebral body on adjacent segments and the influence of force transmission mode after the dynamic cervical implant(DCI)surgery.Two types of surgery,DCI implantation and interbody fusion were used to establish the finite element model of the cervical C5,6segment degeneration treatment.The ROM and the adjacent discs and vertebral body stresses of two procedures under flexion,extension,lateral bending and axial rotation working conditions were analyzed.The results showed that ROM of the surgical segment in DCI model was well preserved and could restore to the normal ROM distributions(reduction of the amplitude was less than 25%),and the kinetic characteristics of adjacent segments was less affected.In fusion surgery model,however,ROM of the surgical segment was reduced by 86%-91%,while ROM,disc stress and vertebral stress of adjacent segments were increased significantly,and stress of the C5 vertebral body was increased up to 171.21%.Therefore DCI surgery has relatively small influence on cervical ROM and stress.The study provides a theoretical basis for DCI and fusion surgery in clinic.

[Biomechanical research of transforaminal lumbar interbody fusion model].

Based on the surgical model using transforaminal lumbar interbody fusion (TLIF) to treat lumbar spondylolisthesis, this paper presents the investigations of the biomechanical characteristics of cage and pedicle screw in lumbar spinal fusion implant fixed system under different combinations with finite element method. Firstly, combining the CT images with finite element pretreatment software, we established three dimensional nonlinear finite element model of human lumbar L4-L5 segmental slight slippage and implant under different fixed combinations. We then made a comparison analysis between the biomechanical characteristics of lumbar motion range, stress distribution of cage and pedicle screw under six status of each model which were flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation. The results showed that the motion ranges of this model under different operations were reduced above 84% compared with those of the intact model, and the stability of the former was improved significantly. The stress values of cage and pedicle screw were relatively larger when they were fixed by single fusion device additional unilateral pedicle screw, but there was no statistically significant difference. The above research results would provide reference and confirmation for further biomechanics research of TLIF extracorporal specimens, and finally provide biomechanical basis for the feasibility of unilateral internal fixed diagonal intervertebral fusion TLIF surgery.

[Construction and analysis of a finite element model of human L4-5 lumbar segment].

In the present study, a finite element model of L4-5 lumbar motion segment was established based on the CT images and a combination with image processing software, and the analysis of lumbar biomechanical characteristics was conducted on the proposed model according to different cases of flexion, extension, lateral bending and axial rotation. Firstly, the CT images of lumbar segment L4 to L5 from a healthy volunteer were selected for a three dimensional model establishment which was consisted of cortical bone, cancellous bone, posterior structure, annulus, nucleus pulposus, cartilage endplate, ligament and facet joint. The biomechanical analysis was then conducted according to different cases of flexion, extension, lateral bending and axial rotation. The results showed that the established finite element model of L4-5 lumbar segment was realistic and effective. The axial displacement of the proposed model was 0.23, 0.47, 0.76 and 1.02 mm, respectively under the pressure of 500, 1 000, 1 500 and 2 000 N, which was similar to the previous studies in vitro experiments and finite element analysis of other people under the same condition. The stress distribution of the lumbar spine and intervertebral disc accorded with the biomechanical properties of the lumbar spine under various conditions. The established finite element model has been proved to be effective in simulating the biomechanical properties of lumbar spine, and therefore laid a good foundation for the research of the implants of biomechanical properties of lumbar spine.

Numerical simulation of the inhibitory effect of angiostatin on metastatic tumor angiogenesis and microenvironment.

The present work formulates and analyzes the inhibitory effect of anti-angiogenic factor angiostatin excreted by the primary tumor on metastatic tumor angiogenesis, blood perfusion, and interstitial fluid flow in the tumor microenvironment by means of a numerical experiment. The simulation results demonstrate that angiostatin has an obvious impact on the morphology, growth rate, and the number of branches of microvascular network inside and outside the metastatic tumor, and angiostatin has the capacity to regulate and inhibit the formation of new blood vessels. Heterogeneous blood perfusion, widespread interstitial hypertension, and low convection within the metastatic tumor have obviously improved under the inhibitory effect of angiostatin, which are consistent with physiological observed facts. The simulation results may provide beneficial information and theoretical models for clinical research of anti-angiogenic therapy strategies.

Coupled modeling of blood perfusion in intravascular, interstitial spaces in tumor microvasculature.

The coupling of intravascular and interstitial flow is a distinct feature of tumor microcirculation, due to the high vessel permeability, the low osmotic pressure gradient as well as the absence of functional lymphatic system inside tumors. In this paper, a coupled mathematical model of tumor microcirculation is developed, which provides the link between microvasculature and interstitial space perfusion through the matrices determining a neighbor point belonging to either connected vessel (matrix B) or interstitial space (matrix A), and combines the intravascular and interstitial flow by vascular leaky terms. In addition, the compliance of tumor vessels, blood rheology with hematocritic distribution at branches is also considered. The microvascular network, on which the microcirculation calculation is carried out, is generated from our two-dimensional 9-point (2D9P) model of tumor angiogenesis, improved from the previous 2D5P one. A specific coupling procedure is developed in the study to couple the intravascular and interstitial flow. It is based on the iteratively numerical simulation techniques, including local iterations at individual parameter level and one global loop to provide coupling and simulation convergence. The simulation results not only present the basic features and characteristics of tumor microcirculation, which agree with the corresponding experimental observations reported, but also predict an intimate relationship between the tumor intravascular and interstitial flow quantitatively. Among the parameters, the vascular leakiness is a key to govern the systemic flowing pattern, influence the tumor internal environment and contribute to the metastasis of tumor cells, which could not be presented by the previous uncoupled models.