Effects of CXC-chemokine Receptor 7 Expression in Endothelial Progenitor Cells on Angiogenesis after Cerebral Ischemia-reperfusion Injury / 中国康复理论与实践

Objective:To explore the effect of upregulating CXC-chemokine receptor 7 (CXCR7) in endothelial progenitor cells (EPCs) on angiogenesis after cerebral ischemia-reperfusion injury. Methods:EPCs were isolated and cultured from human umbilical cord blood and identified. Then, the EPCs were transfected with CXCR7 overexpression lentiviral vector, and the expression of CXCR7 was identified with real-time PCR and Western blotting. The tube-like structure formation and apoptosis of EPCs under oxidized low density lipoprotein (ox-LDL) were detected with tube-like structure formation test and Annexin V/PI staining. Cerebral ischemia-reperfusion injury model in rats was established, and the qualified model rats were randomly divided into three groups after 24 hours reperfusion: PBS group (n = 12) was injected with phosphate buffers through tail vein, control group (n = 12) was injected the EPCs infected with control lentiviral vector, and CXCR7 group (n = 12) was injected with EPCs infected with CXCR7 overexpression lentiviral vector. Neurological function scores were determined seven and 14 days after transplantation. The cerebral infarct volume was measured, the number of GFP-positive cells in the ischemic site and the density of capillary were observed. Results:The expression of CXCR7 in EPCs increased after transfection (P < 0.01). Overexpression of CXCR7 improved tube formation and reduced apoptosis of EPCs under ox-LDL (P < 0.05). Compared with PBS and control groups , neurological function improved in CXCR7 group, with less infarct volume, more GFP-positive cells and density of capillary (P < 0.05). Conclusion:Up-regulating CXCR7 can improve the survival and angiogenesis of EPCs, and improve the repair of cerebral ischemia-reperfusion injury.

Static and gait finite element analysis on individualized titanium alloy pelvic prosthesis manufactured by 3D printing / 医用生物力学

Objective To evaluate the biomechanical properties of 3D printed individualized titanium alloy pelvic prosthesis in static and gait states by the method of finite element analysis. Methods Three patients with different types of pelvic tumors were treated by hemi-pelvic arthroplasty with resection of hemi-pelvis. CT and MRI were performed before the surgery, and the corresponding individualized titanium alloy pelvic prostheses were designed. The pelvic models were reconstructed with 3D reconstruction technique, and then assembled with the individualized pelvic prostheses. The human skeletal muscle model was established by AnyBody software to perform gait dynamics analysis. The stress distribution and stress concentration areas of 3 reconstructed pelvic models in static and gait states were obtained by ABAQUS. Results Under both static and gait conditions, the maximum stress of the 3 pelvic prostheses was smaller than the yield strength of the titanium alloy. The pelvic ring of the reconstructed pelvis could meet the rule of stress conduction. The patients’ daily life returned to normal condition after the surgery. Conclusions The effect of 3D prosthetic titanium prosthesis on recovery of pelvic ring is satisfactory, and its effectiveness and stability can meet the requirement of human biomechanics. The analytic results can provide references for clinicians and prosthesis designers.

Biomechanical properties of cervical traction under neck muscle force / 医用生物力学

Objective To establish a three-dimensional(3D) finite element model of cervical vertebrae (C1-7), and study its biomechanical properties under muscle force by cervical traction, so as to provide references for clinical treatment. Methods On the basis of nonlinear finite element model of normal cervical vertebrae and combined with clinical traction methods, cervical traction at the extension angle of 0°, 10°, 20°, 30°, 40° under the same traction weight, was simulated by finite element analysis (FEA) software to obtain and select the joint force and muscle force that were appropriate for FEA on the model. Results In the process of cervical extension by traction, under the muscle force, the average maximum equivalent stress of cervical vertebrae, intervertebral disc and uncovertebral joints increased by 4.86, 1.79, 0.69 MPa, respectively, and the average maximum relative displacement of cervical vertebrae in sagittal and vertical axis direction increased by 11.1, 1.26 mm, respectively. The biomechanical properties of cervical traction were similar to the FEA results reported in the literature. Conclusions Neck muscles play an active role in promoting the stress and displacement of cervical vertebrae, intervertebral discs and uncovertebral joints and it should be taken into consideration when performing cervical traction in clinic. In addition, the traction angle should not be too large: 0°-20° is generally recommended as a relatively safe angle range at the initial stage.

Static and gait finite element analysis on individualized titanium alloy pelvic prosthesis manufactured by 3D printing / 医用生物力学

Objective To evaluate the biomechanical properties of 3 D printed individualized titanium alloy pelvicprosthesis in static and gait states by the method of finite element analysis.Methods Three patients with different types of pelvic tumors were treated by hemi-pelvic arthroplasty with resection of hemi-pelvis.CT and MRI were performed before the surgery,and the corresponding individualized titanium alloy pelvic prostheses were designed.The pelvic models were reconstructed with 3D reconstruction technique,and then assembled with the individualized pelvic prostheses.The human skeletal muscle model was established by AnyBody software to perform gait dynamics analysis.The stress distribution and stress concentration areas of 3 reconstructed pelvic models in static and gait states were obtained by ABAQUS.Results Under both static and gait conditions,the maximum stress of the 3 pelvic prostheses was smaller than the yield strength of the titanium alloy.The pelvic ring of the reconstructed pelvis could meet the rule of stress conduction.The patients' daily life returned to normal condition after the surgery.Conclusions The effect of 3D prosthetic titanium prosthesis on recovery of pelvic ring is satisfactory,and its effectiveness and stability can meet the requirement of human biomechanics.The analytic results can provide references for clinicians and prosthesis designers.

Biomechanical properties of cervical traction under neck muscle force / 医用生物力学

Objective To establish a three-dimensional(3D) finite element model of cervical vertebrae (C1-7),and study its biomechanical properties under muscle force by cervical traction,so as to provide references for clinical treatment.Methods On the basis of nonlinear finite element model of normal cervical vertebrae and combined with clinical traction methods,cervical traction at the extension angle of 0°,10°,20°,30°,40° under the same traction weight,was simulated by finite element analysis (FEA) software to obtain and select the joint force and muscle force that were appropriate for FEA on the model.Results In the process of cervical extension by traction,under the muscle force,the average maximum equivalent stress of cervical vertebrae,intervertebral disc and uncovertebral joints increased by 4.86,1.79,0.69 MPa,respectively,and the average maximum relative displacement of cervical vertebrae in sagittal and vertical axis direction increased by 1 1.1,1.26 mm,respectively.The biomechanical properties of cervical traction were similar to the FEA results reported in the literature.Conclusions Neck muscles play an active role in promoting the stress and displacement of cervical vertebrae,intervertebral discs and uncovertebral joints and it should be taken into consideration when performing cervical traction in clinic.In addition,the traction angle should not be too large:0.-20. is generally recommended as a relatively safe angle range at the initial stage.

Biomechanical properties of cervical traction under neck muscle force / 医用生物力学

Objective To establish a three-dimensional(3D) finite element model of cervical vertebrae (C1-7),and study its biomechanical properties under muscle force by cervical traction,so as to provide references for clinical treatment.Methods On the basis of nonlinear finite element model of normal cervical vertebrae and combined with clinical traction methods,cervical traction at the extension angle of 0°,10°,20°,30°,40° under the same traction weight,was simulated by finite element analysis (FEA) software to obtain and select the joint force and muscle force that were appropriate for FEA on the model.Results In the process of cervical extension by traction,under the muscle force,the average maximum equivalent stress of cervical vertebrae,intervertebral disc and uncovertebral joints increased by 4.86,1.79,0.69 MPa,respectively,and the average maximum relative displacement of cervical vertebrae in sagittal and vertical axis direction increased by 1 1.1,1.26 mm,respectively.The biomechanical properties of cervical traction were similar to the FEA results reported in the literature.Conclusions Neck muscles play an active role in promoting the stress and displacement of cervical vertebrae,intervertebral discs and uncovertebral joints and it should be taken into consideration when performing cervical traction in clinic.In addition,the traction angle should not be too large:0.-20. is generally recommended as a relatively safe angle range at the initial stage.

Variation of neck EMG and mechanical characteristics during the process of cervical traction / 医用生物力学

Objective To observe changes of surface electromyography (sEMG) in cervical traction under different loading weight and at different angles, and compare the muscle activity changes obtained by experiment with simulation results obtained by AnyBody cervical modeling, so as to verify the rationality of the simulation results. Methods Ten young volunteers with supine cervical traction were selected to test the sEMG signals of bilateral sternocleidomastoid (SCM) and upper trapezius (UT) muscles by using the JE-TB0810 surface EMG device. The average EMG (AEMG) and mean power frequency (MPF) were used to analyze the variation patterns of sEMG in cervical spine. Results The AEMG values of SCM and UT muscles increased as the loading weight and traction angles increasing, with a statistically significant difference (P0.05). The experimental results were consistent with muscle force activity characteristics of SCM and UT muscles by modeling and simulation of cervical traction. Conclusions The simulation results are reasonable. The traction weight should be loaded reasonably according to the excitation and fatigue of the cervical muscles in clinic. This can both reach the treatment effect and improve the patient’s comfort, which will provide an important reference for further development and improvement of the cervical traction device.

Biomechanical properties of calcium silicate/calcium phosphate cement scaffolds with controllable porous structure for bone repair by 3D bioplotting / 医用生物力学

Objective To design and fabricate novel mesoporous calcium silicate/calcium phosphate cement (MCS/CPC) scaffolds for bone repair and investigate their in vitro biomechanical properties under different external forces. Methods MCS and CPC in certain proportion were mixed to form plotting material, and the composite MCS/CPC scaffolds with pore size of 350 μm and 500 μm were fabricated by 3D bioplotting technique, respectively. Surface topographies of the scaffolds were observed by scanning electron microscope (SEM). The compressive strength and mechanical properties of the scaffolds under dynamic cyclic loads at different frequencies were studied through universal mechanical testing machine and dynamic mechanical analysis instrument. Results MCS/CPC scaffolds with controllable macroporous structures could be fabricated by 3D bioplotting technique. Scaffolds with pore size of 350 μm had higher compressive strength ［(9.8±0.39) MPa］ and compressive modulus ［(132.5±4.3) MPa］. In addition, at the loading frequency of 1-100 Hz, scaffolds with pore size of 350 μm had a higher storage modulus. ConclusionsMCS/CPC scaffolds with pore size of 350 μm fabricated by 3D bioplotting technique possess not only regular pore connectivity and high compressive strength, but also structural stability under dynamic loads, which are promising as novel biomaterials for bone repair.

Biomechanical analysis and reasoning on aseptic loosening failure after total hip arthroplasty / 医用生物力学

Objective To propose some detailed methods for diagnosis of aseptic loosening failure in clinic by studying the mechanical mechanism and the specific causes of aseptic loosening failure after the total hip arthroplasty (THA). Methods The causes of aseptic loosening were investigated from the view of biomechanics, such as strength of the bone cement layer, interface fretting, stress shielding, wear and osteolysis; the relationships between aseptic loosening failure and products, clinical and patient factors were analyzed; the method to detect loosening before the revision surgery was also studied. Results The reasoning route for aseptic loosening failure analysis after THA was proposed, and detection of aseptic loosening with fluoroscopic analysis (FSA) technique before the revision surgery was conducted successfully. Conclusions The reasoning route for aseptic loosening failure analysis can help to discover reasons of failure occurrence. Loosening can be detected and confirmed in vivo by FSA method, which can also assist the clinician for diagnosis and treatment of aseptic loosening after the THA.

Mechanical analysis and reasoning on fractured stem failure after total hip arthroplasty / 医用生物力学

Objective To propose some detailed methods for diagnosis of fractured stem failure in clinic by studying the mechanical mechanism of fractured stem failure and the specific causes of fracture occurrence after the total hip arthroplasty (THA). Methods The correlations between fracture stem failure and production, clinical situation and patients were analyzed by 2D and 3D finite element analysis (FEA) method to study the biomechanical mechanism of fracture processes. Results The reasoning route for fractured stem failure analysis after THA was proposed, and mechanical analysis and validation on fractured stem failure were conducted by FEA methods successfully. Conclusions Fracture should not occur on the artificial stem, for those that gone through the strength design and experimental test; statistical analysis on fractured stem failure showed that the occurrence of such fractured stem is a kind of little probability random event, which could be induced by a variety of non-normal factors, such as fluctuations in product quality, technical errors in clinic, patient accidents and so on. Strict controls on these factors can reduce the fractured stem occurrence; the reasoning route for fractured stem failure can help to discover the reasons of failure occurrence; the mechanical mechanism of specific fracture stem occurrence can be detected by 2D and 3D FEA methods.

Biomechanical analysis and reasoning on dislocation failure after total hip arthroplasty / 医用生物力学

Objective To propose a detailed method on the diagnosis of dislocation failure by studying the mechanism of mechanical failure and causes of dislocation occurrence after the total hip arthroplasty (THA). Methods The correlation between dislocation failure and clinical situation, product design and patients was analyzed by establishing the dislocation model to study the biomechanical mechanism of dislocation procedure. Results The reasoning route for dislocation analysis after THA was proposed and the visual hip prosthesis motion analysis software was developed and validated. Conclusions Case study on dislocation failure after THA shows that the proposed method and developed software can judge the cause of dislocation incidence in detail, and determine the relationship between implanting position for the hip prosthesis and dislocation incidence. Meanwhile, it can find the best implanting position before operation and analyze the risk of dislocation incidence, which will be helpful for the prosthesis design.

Wear analysis and diagnostic reasoning on clinical failure of artificial hip joints / 医用生物力学

Objective To investigate the wear mechanism of artificial hip joints and the criteria for wear life definition, analyze the causes of abnormal wear and the clinical manifestations of wear failure, establish the reasoning route of failure incidents. Methods The wear process and early factors on abnormal wear in artificial hip joints were studied through elastohydrodynamic lubrication computation and finite element analysis; the service life of artificial hip joints was determined through establishing criteria for wear life definition; the clinical manifestations of wear failure were introduced and classified through wear-osteolysis morphological matrix; the reasoning logic of failure incidents was established through clinical investigation. Results The minimal synovium thickness and contact stress between the femoral head and the acetabular cup were calculated, and the effect of relevant parameters was studied as theoretical references for wear analysis; the criteria on wear life definition of artificial hip joints were proposed, namely the mechanistic failure due to geometric change in artificial hip joints and the biological failure due to osteolysis; nine kinds of clinical manifestation for wear failure were found; the reasoning route for failure incidents was presented. Conclusions Primary wear process in artificial hip joints includes boundary and mixed friction, adhesive, ploughing and third-body wear; surface quality, fit clearance between the acetabular cup and the femoral head, and roundness have great impact on early abnormal wear; normal mechanistic life of metal-UHMWPE artificial hip joint can reach 40 years, but its maximum biological life is no more than 10-15 years, which is the constraint of prosthesis life today; the diversity of clinical manifestations for wear failure is the morphological Results of mechanical wear and osteolysis, which is helpful for the reasoning route of failure incidents.

Anatomical and biomechanical analysis of sacral pedicle and lateral mass / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To study the anatomical and biomechanical features of sacral pedicle and lateral mass so as to provide reference for clinical screw fixation technology of sacral pedicle and lateral mass.</p><p><b>METHODS</b>A total of 60 adult patients'spiral CT images of the sacrum and coccyx were selected randomly. The entry points of sacral pedicle and lateral mass screws were determined, and the screw trajectory was measured using the three dimensional reconstruction method. Meanwhile, the gross anatomy was scrutinized in 15 adult cadaver specimens to determine the sacral pedicle and lateral mass screw entry points. The length, width and angle of sacral pedicle and lateral mass screw trajectory were measured. Eight of 15 cadaver specimens were selected to test the maximal extraction force of sacral pedicle and lateral mass screws. The clinical data of 15 cases treated by pedicle and lateral mass screw technology were collected and analyzed.</p><p><b>RESULTS</b>The diameter and length of S(1)-S(5) sacral pedicle and lateral mass screw trajectory were regular, with about 20 degree inclination angle. The S(1) pedicle screw entry point was located at the intersection point of the basal lateral part of articular process and median line of transverse process, and no significant difference was found for the maximal extraction force between pedicle and lateral mass screws (P larger than 0.05). The entry points of S(2)-S(5) pedicle screws were located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of the transverse process. The lateral mass screw entry point of S(2)-S(5) was on the median side of intersection point between median line of the transverse process and lateral sacral crest. The maximal extraction force of pedicle screws was significantly greater than that of lateral mass screws (P less than 0.05).</p><p><b>CONCLUSION</b>Both the sacral pedicle and the lateral mass screw fixation techniques can offer effective fixation and reconstruction for fracture of the sacrum and coccyx, but pedicle screw fixation may be more convenient, safe and reliable than lateral mass screw fixation.</p>

An experimental study of artificial murine bladder reflex arc established by abdominal reflex / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The neurogenic bladder dysfunction caused by spinal cord injury is difficult to treat clinically. The aim of this research was to establish an artificial bladder reflex arc in rats through abdominal reflex pathway above the level of spinal cord injury, reinnervate the neurogenic bladder and restore bladder micturition.</p><p><b>METHODS</b>The outcome was achieved by intradural microanastomosis of the right T13 ventral root to S2 ventral root with autogenous nerve grafting, leaving the right T13 dorsal root intact. Long-term function of the reflex arc was assessed from nerve electrophysiological data and intravesical pressure tests during 8 months postoperation. Horseradish peroxidase (HRP) tracing was performed to observe the effectiveness of the artificial reflex.</p><p><b>RESULTS</b>Single stimulus (3 mA, 0.3 ms pulses, 20 Hz, 5-second duration) on the right T13 dorsal root resulted in evoked action potentials, raised intravesical pressures and bladder smooth muscle, compound action potential recorded from the right vesical plexus before and after the spinal cord transaction injury between L5 and S4 segmental in 12 Sprague-Dawley rats. There were HRP labelled cells in T13 ventral horn on the experimental side and in the intermediolateral nucleus on both sides of the L6-S4 segments after HRP injection. There was no HRP labelled cell in T13 ventral horn on the control side.</p><p><b>CONCLUSION</b>Using the surviving somatic reflex above the level of spinal cord injury to reconstruct the bladder autonomous reflex arc by intradural microanastomosis of ventral root with a segment of autologous nerve grafting is practical in rats and may have clinical applications for humans.</p>

Anatomical and Biomechanical Study of Sacral Pedicle and Lateral Mass / 医用生物力学

Objective To study the anatomical and biomechanical features of sacral pedicle and lateral mass to provide evidence for clinical sacral pedicle and lateral mass screw fixation technology. Method 60 adult patient's spiral CT images of sacrum and coccyx were selected randomly. The sacral pedicle and lateral mass screw entry point was determined, and the crew trajectory were measured using the three dimensional reconstruction. Meanwhile, the gross anatomy was done for 15 adult cadavers to determine the sacral pedicle and lateral mass screw entry point. The length, width and angle of sacral pedicle and lateral mass screw trajectory was measured. 8 of 15 cadaver specimens were selected to test for the maximal extraction force for sacral pedicle and lateral mass screws. ResultsThe diameter and length of S1～S5 sacral pedicle and lateral mass screw trajectory are significantly regular, with inclination angle is about 20°. The S1 pedicle screw entry point is located at intersection point of basal lateral part of articular process and median line of transverse process, no significant difference is found between the maximal extraction force of pedicle and lateral mass screws (P>0.05）. The entry points of S2～5 pedicle screws are located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of transverse process. The lateral mass screw entry point of S2～5 is on the median side of intersection point between median line of transverse process and lateral sacral crest. The maximal extraction force of pedicle screws are significantly different from the lateral mass screws（P<0.05）. Conclusions Both the sacral pedicle and the lateral mass screw fixation technology can offer effective fixation and reconstruction for the fracture of sacrum and coccyx, but the pedicle screw fixation may be more convenient, safe and reliable than the lateral mass screw fixation technology.