Biomechanical Study on Atlantoaxial Dislocation Combined with Basilar Invagination by Different Posterior Internal Fixation Methods / 医用生物力学

Objective To investigate biomechanical differences of two posterior occipitocervical internal fixation techniques for treating basilar invagination with atlantoaxial dislocation (BI-AAD). Methods Intra-articular cage + posterior occipital plate+C2 pedicle screw (Cage+C2PS+OP), and intra-articular cage+C1 lateral mass screw+C2PS (Cage+C1LMS+C2PS) models were established based on occipitocervical CT data of the BI-AAD and clinical operation scheme, and the stability of atlantoaxial joint and stress distribution characteristics of C2 endplate and implanted instruments under different motion states were analyzed. Results Compared with the Cage+C1LMS+C2PS model, the atlantoaxial range of motion ( ROM) under flexion, extension, lateral bending and axial rotation in the Cage+C2PS+OP model were reduced by 5. 26% , 33. 33% , 43. 75% , -5. 56% , and stress peak of screw-rod fixation system were reduced by 47. 81% , 60. 90% , 48. 45% , 39. 14% , respectively. Under two internal fixation modes, stresses of C2 endplate and cage were mainly distributed on the compressive side during the motion, and both the screw-bone interface and the caudal side of screw subjected to large loading. Conclusions Two internal fixation methods could provide similar stability. However, the stress concentration of screw-rod system was more obvious and the possibility of screw loosening and fracture was greater under Cage+ C1LMS+C2PS fixation.

Mathematical Model of Tumor Growth in Radiotherapy and Radiosensitivity Analysis / 医用生物力学

Objective To establish a mathematical model of tumor growth and invasion under radiotherapy, so as to numerically simulate the effect of radiotherapy on tumor growth and make sensitivity analysis.Methods The mathematical model of tumor growth and invasion with time evolution before and after radiotherapy was established. The model included four key variables in the process of tumor invasion: tumor cells, extracellular matrix (ECM), matrix-degradative enzymes (MDEs) and oxygen. The linear quadratic (LQ) model was used to simulate the survival probability of tumor cells after radiotherapy, and the effects of different radiotherapy schemes and radiotherapy coefficients on the treatment effect were discussed. Traditional radiotherapy and intraoperative targeted radiotherapy were compared.Results Under the premise of constant total dose, the results of radiotherapy were directly proportional to the radiotherapy coefficient, but not related to the radiotherapy frequency; the therapeutic effect of intraoperative targeted radiotherapy was better than that of standard treatment.Conclusions Simulation results are basically consistent with clinical experimental results. As a more efficient treatment method, intraoperative targeted radiotherapy can provide new ideas for clinical tumor treatment.

Effects of Different Posterior Tibial Slopes in Unicompartmental Knee Arthroplasty on the Wear and Function of Prosthesis / 医用生物力学

Objective To establish the three-dimensional (3D) finite element model of unicompartmental knee arthroplasty (UKA) with 3° and 7° posterior tibial slope at different knee flexion angles, and to study biomechanical properties and prosthetic wear of the knee joints with two types of posterior tibia slope and their effects on knee function. Methods Combining CT and MRI images of human knee joints with the 3rd-generation Oxford prosthesis, the finite element UKA model with 3° and 7° posterior tibia slope were established. The 1 kN load was applied to center point of the medial and lateral condyles of the femur to simulate the standing load of human body. The maximum stresses and distributions of the prosthesis and articular cartilage at different knee flexion angles were analyzed. ResultsThe maximum stress of the meniscus liner with 3° posterior tibia slope at 0°, 30°, 60°, 90°, 120° knee flexion angles increased by 28.06%, 68.99%, 19.45%, 21.06% and 53.38%, the distribution area was concentrated from the side of the meniscus liner to the central area, and the stress concentration was obvious at 120° knee flexion. The maximum stress of prosthesis with 3° posterior tibia slope was greater than that with 7 ° posterior tibia slope. The expansion of stress concentration area would cause wear and loosening of the prosthesis, contact stress and concentration area of the articular cartilage would subsequently increase with posterior tibia slope increasing, and stress concentration would be more obvious at high knee flexion angles. Conclusions Tibial prosthesis has the higher stress and greater wear under the condition of 3° posterior tibia slope than 7° posterior tibia slope. The research findings provide theoretical basis for the UKA design in clinic.

Effects of Cervical Fusion Surgery by Different Methods on Stability in Upper Cervical Spine with Jefferson Fracture / 医用生物力学

Objective To establish the finite element model of upper cervical vertebrae C0-3 with Jefferson fracture, and to analyze the influence of posterior atlantoaxial fusion (PSF) and occipitocervical fusion (OCF) on biomechanical properties of the vertebral body and mechanical conduction of the screw-rod system. Methods Based on CT images, the C0-3 segment Jefferson fracture model of human upper cervical spine was established. PSF, OCF1 and OCF2 internal fixation were performed according to surgical plan in clinic, and 50 N concentrated force and 1.5 N·m torque were applied to bottom of the occipital bone. The stress distribution and range of motion (ROM) of the cervical vertebral body, the maximum stress of the screw-rod system and the stress distribution of the intervertebral disc for C0-3 segment during flexion, extension, bending and rotation of the upper cervical spine were studied. Results Compared with PSF, the ROM of OCF1 and OCF2 vertebral bodies increased, and the stress of the nail rod decreased. OCF had a better fixation effect. Conclusions PSF, OCF1 and OCF2 fixation method can reduce the upper cervical ROM and restore stability of the upper cervical spine, which make stress distributions of the vertebral body and intervertebral disc tend to be at normal level. The research result can provide a theoretical basis for clinical surgery plan.

Finite Element Analysis on Biomechanical Properties of Unicompartmental Knee Arthroplasty in ACL Fracture of the Knee Joint / 医用生物力学

Department of Orthopedics, Yang Pu Hospital Affiliated to Tongji University,

Effects of ROI-C Cervical Implantation on Biomechanics of Cervical Vertebra / 医用生物力学

Objective To investigate the influence of ROI-C cervical implantation in the C5-6 segment on the C3-7 range-of-motion (ROM), biomechanical properties of the intervertebral disc and the vertebral body, and the mode of force transmission. Methods Two types of surgeries, ROI-C implantation and autograft fusion with plate fixation, were considered to establish the finite element model of cervical C5-6 segment degeneration. The ROM of C3-7 during flexion, extension, lateral bending, and axial rotation, as well as stress distributions on the adjacent discs, vertebral body, and implanted devices under two procedures, were analyzed. Results ROI-C implantation had a relatively small influence on the ROM of the adjacent segment. The stress on the vertebral discs was reduced, but the stress on the vertebral body increased significantly, with the C5 vertebral body stress increasing by 251%. In the fusion surgery model, the ROM of the surgical segment was reduced by 86%-91%, while the ROM of the adjacent segments and the stress on the vertebral disc and vertebral body increased significantly. Conclusions ROI-C implantation surgery has a relatively small influence on the cervical ROM and the intervertebral disc, and it has a greater impact on the vertebral body. The research findings provide a theoretical basis for the design of operation plans and clinical studies on ROI-C implantation and autograft fusion with plate fixation.

Finite element analysis on lower cervical spine by anterior cervical corpectomy and fusion sugery / 医用生物力学

Objective To establish the three-dimensional finite element model of human lower cervical spine C3-7 motion segments after anterior cervical corpectomy and fusion (ACCF) surgery with titanium mesh and bone graft,and to analyze the stability of cervical spine and stress distribution of internal fixation devices after ACCF surgery.Methods The finite element model of cervical spine C3-7 segments after ACCF of C5 segment with titanium mesh,bone graft,plate and screw fixation was established,and C3-7 segment intact model of cervical vertebra was also constructed.The torque moment of 0.5,1.0,1.5,2.0 N · m was applied to the ACCF surgery model.The ROM,maximum stress in facet joint and stress distributions on internal fixation devices under flexion,extension,lateral bending and axial rotation movement were analyzed.Results ROM of reconstructed C5 segment increased with the torque moment increasing after ACCF surgery.In the case of 1.0 N · m tomue moment and 50 N preload,the ROM of reconstructed C5,C3-4,C6-7 and C3-7 segment was reduced by 81％,62％,58％ and 80％ compared with the intact model.The maximum stress in facet joint of reconstructed C5 segment reduced and the stress in adjacent segments significantly increased.The stress of titanium mesh was mainly distributed on the compression side of movement,and high stress was located in the roots of screws.Conclusions ACCF surgery can promote the stability of cewical spine,decrease the stress in facet joint of operation segment,and has better treatment effect on easing compression from spinal cord caused by cervical spondylotic myelopathy.The research results will provide some theoretical basis for clinical application of ACCF surgery.

Biomechanical research of transforaminal lumbar interbody fusion model / 生物医学工程学杂志

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 / 生物医学工程学杂志

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.

The assessment of gastric emptying function of diabetic gastroparesis by gastroenteric contrastenhanced ultrasonography / 中国医师进修杂志

Objective To detect the changes of gastric emptying function by gastroenteric contrastenhanced ultrasonography and to offer the evidence for the diagnosis and treatment of diabetic gastroparesis.Methods The gastric emptying function was measured by gastroenteric contrast-enhanced ultrasonography in 35 cases of diabetic gastroparesis (DGP,DGP group) and 35 volunteers (control group).The gastric emptying rate(GER) and emptying time(ET) after taking orally gastroenteric ultrasound developer in DGP group were observed and compared with control group.Results The GER in DGP group was lower than that in control group [(27.05 ± 11.32)％ vs.(45.38 ± 15.08) ％] (P ＜ 0.05).The ET in DGP group was longer than that in control group[(102.43 ± 15.76) min vs.(75.31 ± 11.52) min] (P ＜ 0.05).Conclusions The method of gastroenteric contrast-enhanced ultrasonography is a simple,and repeatable imaging method,which can be used to make a real-time assessment on the gastric dynamic changes,but don't influence gastroenteric function and can provide a dependent and noninvasive examine means for clinical physician to test the gastric emptying function in DGP.

Curative effect and complications of uterine arterial embolization therapy for leiomyom of uterus with three different embolization agents / 中国医师进修杂志

Objective To evaluate the curative effect,adverse reactions and complications of transcatheter uterine arterial embolization (TUAE) therapy for leiomyoma of uterus with three different embolization agents: silk particles, pingyangmycin-lipiodol emulsion (PLE), polyvinyl alcohol (PVA).Methods One hundred and twenty-six patients of uterus leiomyoma were included, who undergoing TUAE treatment with silk particles(54 cases, silk particles group) ,PLE(40 cases,PLE group) and PVA(32 cases, PVA group) respectively.Adverse reactions and complications were recorded until 6-60 months after TUAE treatment.Measured the volume of the leiomyoma by ultrasonic inspection or enhanced computed tomography (CT).Results All clinical symptoms of three groups were relieved, and the volumes of uterus leiomyoma after TUAE treatment of 6,12,24 months in PVA group [(50.84 ± 30.77), (39.92 ± 25.72), (31.24 ± 30.60) cm~3]were less than those in PLE group[(76.24 ± 31.16), (58.21 ± 32.05), (52.48 ± 31.41 ) cm~3]and silk particles group[(69.22 ± 36.22), (68.31 ± 32.42), (68.01 ± 30.12) cm~3].The inferior belly and perineal region pain were most slight in silk particles group, but no significant difference in complications was observed in three groups.The symptom recurrence was 3 cases, 2 cases in silk particles group and 1 case in PIE group.Conclusions Clinical outcome of TUAE treatment with all the three embolization agents is acceptable.Adverse reactions and complications are associated with volume of the leiomyoma and the area being embolized.PVA is superior in prevention of complications and relapse of uterus leiomyoma after TUAE treatment.

Trabecular bone porosity measurement based on digital image processing / 中国组织工程研究

BACKGROUND: Traditional cancellous bone porosity detection methods such as direct method,gas expansion method,mercury injection method,density and osmotic suction measurement have many disadvantages,such as low efficiency,labor-intensive and complexity.OBJECTIVE: To process cancellous bone chips using MATLAB image processing method to calculate cancellous bone porosity.METHODS: Using MATLAB image processing method,the stained cancellous bone images were subjected to uneven lighting removal,image enhancement,binarization,removing interference objectives to obtain binary two-dimensional matrix.RESULTS AND CONCLUSION: Slice image was composed of bone and pore space.The slice image was segmented to calculate its porosity.This solves the problem of the inequality of light intensity and other interferences in image information that affect the statistics.The image processing and analysis methods of bone slices were performed using MATLAB,which can be used for cancellous bone porosity measurements and be used to explore the distribution and variation of porosity.Selecting different regions to calculate the different porosity of each area can be used to analyze the distribution of the pore.This method provides a method for the study of trabecular bone structure.

Kinematic analysis of simulated knee prosthesis / 中国组织工程研究

Knee joint is the largest and most complex joint of human body. Knee prosthesis, as the core component of lower limb, has a great expectation on simulated properties. Based on bionics, this study was designed to analyze kinematic characteristics of simulated knee joint, such as the sliding and rolling ratio of the knee as well as the instantaneous center curve, in order to further investigate an ideal simulated knee joint which was highly similar to normal knee joint. Movement regularity of human knee joint was simplified to introduce biomechanical model of knee joint so as to analyze and deduce formula of sliding ratio, rolling ratio, and instantaneous center curve. The calculation results were compared with parameters of human knee joint, suggesting a high coincidence between simulated and human knee joint. This provides an evidence for analyzing stability of motion and further studying structure and function of simulated knee joint, and this also provides basis for further research artificial simulated leg.

Powered control and performance testing of bionic leg / 中国组织工程研究

The prosthesis is forced by pneumatic artificial muscle, which can swing like human legs by inputting signals such as square waves and trigonal waves.Its swing performance is tested under such triggerings in order to find out a best motivating curve rendering the prosthesis performance almost the same as what human legs do. Compared with the normal human pace graph, the curve matches very well in the ascending edge but quite a discrepancy in the end of descending edge. According analyzing the reasons of the discrepancies, we could know how to ameliorate the design of the next generation of the bionic legs.