Metformin is associated with survival benefit in pancreatic cancer patients with diabetes: a systematic review and meta-analysis.

BACKGROUND: Pancreatic cancer is a highly lethal disease with a poor prognosis while metformin has been associated with a decreased risk of pancreatic cancer. Although the benefit of metformin was observed for pancreatic cancer prevention, it is not clear whether it can also affect the survival of pancreatic cancer patients with type 2 diabetes mellitus. A systematic review and meta-analysis was conducted to assess the effect of metformin on the survival of pancreatic cancer patients with type 2 diabetes mellitus. METHODS: Two independent authors searched PubMed and Web of science up to 08/07/2016. We assessed studies for eligibility, extracted data, and examined their quality, with the primary outcome as overall survival. We used published hazard ratio (HR) available or estimated based on other survival data. We pooled the data and used a random-effect model to combine direct comparisons from included articles. We also investigated treatment effects by different countries, quality and the time of metformin initiation. RESULTS: We found that there was a relative survival benefit associated with metformin treatment compared with non-metformin treatment in both overall survival (OS) ([HR] 0.84; 95% confidence interval [CI]: 0.73 - 0.96). These associations were also observed in subgroups of Asian countries and high quality articles. CONCLUSIONS: Our results support the notion that metformin maybe the best anti-diabetic medicine of choice in patients with pancreatic cancer and concurrent type 2 diabetes mellitus. The perspectives of enhancing survival of pancreatic cancer patients with diabetes mellitus by the use of metformin deserve more attention in future research and clinical practice.

[Femoral tunnel positioning in posterior cruciate ligament double-bundle reconstruction by computer aided design].

OBJECTIVE: To study mechanical affect of knee joint of reasonable positioning of femoral tunnel during knee posterior cruciate ligament (PCL) double-bundle reconstruction and graft fixation after reconstruction by virtual reality interactive technology and evaluate the biomechanical response of knee after reconstruction by finite element analysis. METHODS: Knee specimens from five fresh frozen cadavers were used. Computer simulations and biomechanical experiments were used in this study. Experiments on flexion and extension movements of the knee joint were performed on specimens of fresh human knee joint. Laser three dimensional scanning was used to record and calculate the indexes of movements. Three-dimensional models of knee joint bone structure were then reconstructed on computer with the experimental data. Simulations of flexion and extension movements were carried out on the models to show the spatial positions of femur and tibia and label the attachment sites of PCL. Ten test points in the anterior,posterior, proximal, distal at the femoral attachment area of anterior and lateral bundle (ALB) and postoperior medial bundle (PMB) were selected and the central points of tibial en attachment areat anchored. The distance btween each two points of two article surface was calculated and contacted by software of Geomagic. Model was import software Ansys, adopting the tetrahedron unit a finite element model of complex tibial and femoral was set up to simulat human walking in one leg,on this condition the the joint surface force of model under weight impact load were analyzed. RESULTS: The three-dimensional models could demonstrate the spatial positions of the bone structure of the knee in different flexions and extensions. The models could be used to measure the spatial distance between 2 points on the femoral and tibial planes by software Geomagic. There was significantly difference among the length changes of anterolateral bundle and posteromedial bundle at every fixed point with different flexion angles (P<0.05), so the fixed angle with different points. The length changes of anterior lateral bundle's A2, A1 and posterior medial bundle's B3, B1 points were (1.35±0.19) mm, (5.41±1.22) mm, (1.95±0.04) mm and (5.23±2.21) mm, respectively. The A2 and B3 points' length changes were the less, and that of the Al and B1 points were the more. It had no significant difference between the length changes of anterior lanteral bundle's A2 and A3 point (P=0.913>0.05). All of the maximal length changes of anterior lateral bundle's A2, A3 and postterior medial bundle's B3 points were less than 2 mm. CONCLUSION: The models of knee joint were builded through computer technology and it can be measure the lenth of cruciate ligament with software Geomagic exactly. The femoral tunnel for the PCL double-bundle reconstruction should be located as follows: ALB at the middle point of upper edge of femoral attachment site (proximal point),while PMB at the middle point of femoral attachment site (proximal point). This model provides a satisfactory method for the evaluation of the biomechanical response of knee after cruciate ligament reconstruction.

Biomechanical comparison of osteoporotic distal radius fractures fixed by distal locking screws with different length.

OBJECTIVES: To evaluate the postoperative stability of osteoporotic distal radius fractures fixed with distal locking screws with different length. METHODS: A comminuted extra-articular dorsally unstable distal radius fracture, treated with volar locking plate system, was created. The 18 specimens were randomized into 3 groups based on distal locked screws with different length: Group A had unicortical screws with 50% length to the dorsal cortex. Group B had unicortical screws with 75% length to the dorsal cortex. Group C had bicortical screws. Axial compression and bending loads were imposed on the models before and after cycling testing as well as load to clinical and catastrophic failure. RESULTS: Minimum change in stiffness was observed before and after fatigue for all groups. The final stiffness to bending forces was statistically similar in all groups, but stiffness to axial compression was statistically significant different: Group A approached significance with respect to groups B and C (P = 0.017, 0.009), whereas stiffness in group B and C was statistically similar (P = 0.93). Load to clinical failure was significantly less for group A (456.54±78.59 N) compared with groups B (580.24±73.85 N) and C (591.07±38.40 N). Load to catastrophic failure was statistically similar between groups, but mean values for Group A were 18% less than means for Group C. CONCLUSIONS: The volar locking plate system fixed with unicortical locking screws with at least 75% length not only produced early stability for osteoporotic distal radius fractures, but also avoided extensor tendon complications due to dorsal screw protrusion.

[Three-dimensional finite element analysis on mechanical behavior of the bone remodeling and bone integration between the bone-implant interface after hip replacement].

OBJECTIVE: To discuss the primary stability of the fixed interface between the cementless prosthesis and femur, and its influence on bone ingrowth and secondary stability under the roughened surface and press fit of different prostheses by finite element analysis. METHODS: :A three-dimensional finite element module of total hip arthroplasty (THA) was developed with Mimics software. There was a collection of data when simulating hip arthroplasty. The frictional coefficient between the fixed interface was 0,0.15,0.40 and 1.00 representing the roughness of prosthesis surface. The press fit was 0, 0.01,0.05 and 0.10 mm according to the operation. The Vion Mises stress distribution and the contact pressure,friction stress and relative sliding displacement between the interface were analysed and compared when simulating the maneuver of climbing stairs. RESULTS: At a fixed press fit of 0.05 mm,the contact pressure between the interface was 230 , 231, 222 and 275 MN under four different frictional coefficient (0,0. 15,0.40 and 1.00) with little change; the relative sliding displacement was 0.529, 0.129, 0.107 and 0.087 mm with a consistent and obvious decline. As the fixed frictional coefficient was 0.40,the contact pressure between the interface were 56.0,67.7 ,60.4 and 49.6 MN under four different press fit (0, 0.01, 0.05 and 0.10 mm) with a reduction; the relative sliding displacement was 0.064,0.062,0.043 and 0.042 mm with an obvious decline, and there was a maximal friction stress when press fit of 0.01 mm. CONCLUSION: There is a dynamic process of the bone remodeling and bone integration between the interface after hip replacement, determining the long-term outcome. The interface clearance and the frictional coefficient are the key factors of the bone integration.

Evaluation of biomechanical properties of anterior atlantoaxial transarticular locking plate system using three-dimensional finite element analysis.

PURPOSE: To evaluate a new anterior atlantoaxial transarticular locking plate system using finite element analysis. METHODS: Thin-section spiral computed tomography was performed from occiput to C2 region. A finite element model of an unstable atlantoaxial joint, treated with an anterior atlantoaxial transarticular locking plate system, was compared with the simple anterior atlantoaxial transarticular screw system. Flexion, extension, lateral bending, and axial rotation were imposed on the model. Displacement of the atlantoaxial transarticular screw and stress at the screw-bone interface were observed for the two internal fixation systems. RESULTS: Screw displacement was less using the anterior atlantoaxial transarticular locking plate system compared to simple anterior atlantoaxial transarticular screw fixation under various conditions, and stability increased especially during flexion and extension. CONCLUSIONS: The anterior atlantoaxial transarticular locking plate system not only provided stronger fixation, but also decreased screw-bearing stress and screw-bone interface stress compared to simple anterior atlantoaxial transarticular screw fixation.

Treatment planning of implants when 3 mandibular posterior teeth are missing: a 3-dimensional finite element analysis.

PURPOSE: To analyze the biomechanics of 3 designs of implant treatment for 3 teeth missing in posterior low arch quadrants. MATERIAL AND METHODS: A posterior portion of the human mandible missing 44, 45, 46 and three 4.1 × 10 mm threaded ITI implants with crowns were used to construct the finite element model. According to 3 implants being single, splinted or 2 implants support fixed partial denture (FPD) fixed in bone segments. Three implant support conditions were prepared with ANSYS 10.0. A load of 100 N was applied at the central fossa of the occlusal surfaces of the crowns at 45 degrees buccolingually along the triangular ridge of the buccal cusp. The von Mises stress and strain distributions in periimplant bone were observed. RESULTS: The results demonstrated that the von Mises stress in the supporting bone of the 2-implant supported FPD significantly increased compared with that in the 3-implant replacement. Meanwhile, when 3 implants were splinted, only the median implant had a decreased and more homogenous stress distribution, and the other implants did not exhibit significant differences when splinted. CONCLUSION: This study suggests that when space and cost permit, a 2-implant supported FPD should not be used, and 1 implant for each missing tooth being single is recommended.

[Balloon inflating and cement filling for treatment of avascular necrosis of the femoral head: a three-dimensional infinite-element study].

OBJECTIVE: To evaluate the biomechanical changes of balloon inflating and cement filling in avascular necrosis of the femoral head using finite-element analysis. METHODS: The procedure of percutaneous balloon inflating and cement filling was simulated in fresh specimen of human femoral head. CT scan and three-dimensional reconstruction were used to establish the three-dimensional model of the femoral head. The physiological load was analyzed using three-dimensional finite element model to simulate the load and calculate stress on the hip during walking. Finite element analysis was performed on the avascular necrosis model and balloon inflating and bone cement filling model to measure the Von-Mises force at the top, neck and weight-bearing area of the femoral head. Another 8 fresh specimens of femoral head necrosis of human were obtained to stimulate balloon inflating and bone cement filling procedures, and the displacement of the femoral head under different loads was recorded before and after the procedures. RESULTS: After bone cement filling in the necrosis area, the load reduced significantly in the weight-bearing area of the femoral head, and the load distribution became more uniform at the femoral neck and the top of the head. The anti-deformation ability of the necrosis femoral head increased after bone cement filling. The infinite-element analysis and specimen biomedical test showed similar results. CONCLUSION: Percutaneous balloon inflating and bone cement filling in the necrosis area can change the biomechanics mechanism of the femoral head and neck, improve the supporting capacity under load, and prevent the progression of head collapse.

[Influence of bone quality on the stress distribution for three-posterior immediately loaded implants: a three-dimensional finite element analysis].

OBJECTIVE: To assess and compare the peri-implant stress distribution of three posterior implants under immediate loading with 4 different bone qualities using three dimensional (3D) finite element (FE) analysis. METHODS: A 3D finite element model representing three implants in a portion of mandible at the 654 region was developed, and three implants received a crown each. Four types of bone qualities (B1, B2, B3 and B4) were designed for the model. Load of 100 N was applied on the occlusal surfaces of the crowns at a 45° angle to the vertical axis of the implants. RESULTS: Von Mises stresses in the peri-implant bone of 4 in bone quality from B1 to B4 were (13.17 ± 9.32), (12.95 ± 9.14), (15.00 ± 9.44), and (16.81 ± 10.74) MPa, and those of 5 were (15.51 ± 10.32), (14.73 ± 8.96), (16.79 ± 8.40), and (18.34 ± 8.45) MPa. Stress in bone quality B4 showed the highest value, followed by B3 bone, the lowest stress were found in B1 and B2 bone. It was significantly different (P < 0.05). However, von Mises stresses in different quality of bone around 6 [(42.45 ± 25.71), (41.66 ± 25.29), (42.70 ± 23.24), (42.06 ± 23.66) MPa] were close to each other, and were as twice or three times as those of 4 and 5, irrespective of different bone qualities. CONCLUSIONS: The stress distribution around implant under immediate loading was not only affected by different bone qualities, but also by the direction of loading, and the latter may have a greater impact when a severe load delivered.

[Three-dimensional finite element analysis of biomechanical characteristics of cancellous screw in different bone densities].

OBJECTIVE: To predict the cancellous screw stress distributions and pull-out strength in cancellous bone with different densities using 3-D finite element analysis and provide biomechanical evidence for screw implant in clinical practices. METHODS: Three-dimensional models of bones with low, medium and high bone density and a fixation screw were generated in Solidworks. Finite element analysis was performed after importing these models to Abaqus to simulate the pull- out process. RESULTS: Stress concentrated both at the surfaces where major diameter of the screw connected the bone and at the proximal half angle of the 3 proximal screw threads. Maximum Von Mises stress of the threads decreased along the long axis of the screw. The pull-out strengths of the cancellous screw were 208.9 N, 431.45 N, and 648.80 N in low, medium and high bone density, respectively. CONCLUSION: During the pull-out process of cancellous screw, stress concentrates at the proximal end of the screw and the pull-out strengths are proportional to the cancellous bone density.

Application of computer-aided three-dimensional skull model with rapid prototyping technique in repair of zygomatico-orbito-maxillary complex fracture.

BACKGROUND: With the advent of CAD/CAM and rapid prototyping (RP), a technical revolution in oral and maxillofacial trauma was promoted to benefit treatment, repair of maxillofacial fractures and reconstruction of maxillofacial defects. METHODS: For a patient with zygomatico-facial collapse deformity resulting from a zygomatico-orbito-maxillary complex (ZOMC) fracture, CT scan data were processed by using Mimics 10.0 for three-dimensional (3D) reconstruction. The reduction design was aided by 3D virtual imaging and the 3D skull model was reproduced using the RP technique. In line with the design by Mimics, presurgery was performed on the 3D skull model and the semi-coronal incision was taken for reduction of ZOMC fracture, based on the outcome from the presurgery. RESULTS: Postoperative CT and images revealed significantly modified zygomatic collapse and zygomatic arch rise and well-modified facial symmetry. CONCLUSIONS: The CAD/CAM and RP technique is a relatively useful tool that can assist surgeons with reconstruction of the maxillofacial skeleton, especially in repairs of ZOMC fracture.

Differences of percutaneous retrograde screw fixation of anterior column acetabular fractures between male and female: a study of 164 virtual three-dimensional models.

INTRODUCTION: Percutaneous retrograde screw fixation of the anterior column has been recommended for the treatment of minimally displaced acetabular fractures. However, proper placement of the screw in anterior column is challenging because of its unique anatomy. There are few anatomic studies on this technique, and the differences between male and female have never been reported. METHODS: We created virtual three-dimensional reconstruction models of the pelvis from CT scan data obtained from 82 adult patients without any bony problems. Virtual cylindrical implants were placed intraosseously both in left and right anterior column. The maximum diameter, length and optimal direction of the virtual cylindrical implant were determined for the screw. The perpendicular distance from the insertion point (P) of virtual cylindrical implant to the pubic symphysis (A) and the rim of superior ramus of pubis (B) were measured respectively. In the same model, cross-sections of the anterior column were created and the diameters of them were measured. RESULTS: 164 (80 males and 84 females) hemipelvis models were obtained. The mean maximum diameter and length of virtual cylindrical implant were 8.16+/-1.21 mm (range: 5.60-10.80 mm) and 109.39+/-8.95 mm respectively. The angles of the virtual cylindrical implant to transverse, coronal and sagittal planes were 39.66+/-3.92 degrees , 20.81+/-4.58 degrees and 42.66+/-3.23 degrees respectively. The distance of PA and PB were 18.42+/-4.82 mm and 17.76+/-2.63 mm. Both the differences of the diameter and length of the virtual cylindrical implant, and the distance of PA between the male and female were of statistical significance (p<0.00001). The mean minimum cross-sectional diameter of anterior column was larger than the mean diameter of the virtual cylindrical implant. CONCLUSIONS: The anterior column of a male will accommodate a 6.5mm lag screw very well, but it does not fit all the females. The same direction of screw can be used in both male and female, but the insertion points of the screw are different. In addition, the determination of the size of the screw used for the anterior column cannot be based solely on the measurement of cross-sectional diameter and the virtual three-dimensional reconstruction model might be useful in preoperative planning.

[A finite element investigation of bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation].

OBJECTIVES: To investigate the mechanical properties of bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation with finite element method. METHODS: There was a volunteer with age of 28 years old, body height 172 cm, body weight of 60 kg and without cervical deformity by X rays. The ligamentous, nonlinear, three-dimensional finite element models of normal upper cervical spine (C0-3) was developed and validated. The destabilized model with bilateral atlantoaxial trans-articular screws and atlas laminar hooks was evaluated for quasistatic loading. RESULTS: The finite element model of upper cervical spine consists of 229,047 nodes and 152,475 elements, and correlated well with experimental data for all load cases and could be used for experiment. The finite model with bilateral atlantoaxial trans-articular screws and atlas-laminar hooks predicted that the maximum Von Mises Stress was in the region in which screws penetrated the atlantoaxial articular facet. The novel instrumentation resulted in sufficient stability. CONCLUSION: The bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation is useful and effective for atlantoaxial arthrodesis.

[A three dimensional finite element study on stress distribution in maxillary central incisor restored with fiber post].

OBJECTIVE: To study the stress changes of maxillary central incisor restored with or without fiber post using three dimensional finite element method, and analysis the role of fiber post in determining the stress distribution in dentin. METHODS: Three dimensional finite element models of maxillary central incisor with various remaining tooth structure were established by spiral CT, Mimics software and ANSYS software. Test samples were restored with all-ceramic crown and fiber post all-ceramic crown, respectively. The von Mises stress and maximal tensile stress of dentin were recorded. RESULTS: The stress level in dentin of maxillary central incisor restored with fiber post all-ceramic crown was smaller than that restored with all-ceramic crown, the stress distribution of both were similar. CONCLUSION: The apply of fiber post can reduce the stress level in dentin of maxillary central incisor and decrease the risk of tooth breakage, but not change the stress pattern.

Biomechanical effect of vertebroplasty on the adjacent intervertebral levels using a three-dimensional finite element analysis.

OBJECTIVE: To investigate the biomechanical effect of different volume, distribution and leakage to adjacent disc of bone cement on the adjacent vertebral body by three-dimensional osteoporosis finite element model of lumbar. METHODS: L(4)-L(5) motion segment data of the cadaver of an old man who had no abnormal findings on roentgenograms were obtained from computed tomography (CT) scans. Three-dimensional model of L(4)-L(5) was established with Mimics software, and finite element model of L(4)-L(5) functional spinal unit (FSU) was established by Ansys 7.0 software. The effect of different loading conditions and distribution of bone cement after vertebroplasty on the adjacent vertebral body was investigated. RESULTS: This study presented a validated finite element model of L(4)-L(5) FSU with a simulated vertebroplasty augmentation to predict stresses and strains of adjacent untreated vertebral bodies. The findings from this FSU study suggested the endplate and disc stress of the adjacent vertebral body was not influenced by filling volume of bone cement but unipedicle injection and leakage to the disc of bone cement could concentrate the stress of adjacent endplate. CONCLUSIONS: Asymmetric distributions and leakage of cement into intervertebral disc can improve the stress of endplate in adjacent vertebral body. These results suggest that optimal biomechanical configuration should have symmetric placement and avoid leakage of cement in operation.

[Biomechanical evaluation of nickel-titanium shape-memory alloy enclosed interlocking intramedular nail].

OBJECTIVE: To study the biomechanical characteristics of Ni-Ti shape-memory alloy-enclosed interlocking intramedular nail Ni-Ti En for clinical application. METHODS: Six transverse fractures were induced in 6 fresh humeral shafts and fixed with Ni-Ti En, plate, interlocking intramedullary nail, and Ender nail, respectively. The specimens then underwent stress analysis for comparison of the bending strength, twisting force, and flexibility. RESULTS: The bending strength of Ni-Ti En was not significantly different from that of the plate and better than ender's nail; the twisting force of the interlocking intramedullary nail was comparable with the plate, but better than Ender nail. CONCLUSION: Ni-Ti Enpossess good biomechanical property to meet the demand of osteosynthesis, and its less stress protection, freedom of distant nail locking, flexibility and stable fixation may accelerate fracture healing.

[Establishment of a testing system of three-dimensional spinal kinematics in vivo based on two- and three-dimensional image registration].

OBJECTIVE: To investigate the feasibility of using two- and three-dimensional (2D/3D) image registration for establishing a testing system of 3D kinematics of the spine in vivo. METHODS: CT data of the adult human lumbar spine were collected and the two orthogonal images of the same specimen were captured using an X-ray fluoroscope at two different positions. The 3D computer models of L3 and L4 vertebrae were reconstructed. A virtual fluoroscope was then created with solid modeling software to reproduce the relative positions of the orthogonal images. Two virtual cameras in the software were used to represent the X-ray sources. The 3D computer models of the L3 and L4 vertebrae were then introduced into the virtual fluoroscope respectively and projected onto the orthogonal images by the two virtual cameras. By matching the projections of the 3D model to the orthogonal images of L3 and L4 vertebrae, the 3D positions of L3 and L4 were obtained. After calculation, the relative displacement and angle of L3 were determined. RESULTS: After 2D/3D image registration, the relative displacement and angle were calculated. Compared with position I, the positional changes of L3 were represented with an extension of 5.86 degrees, left bending of 1.85 degrees and right rotation of 2.96 degrees. CONCLUSION: 2D/3D image registration allows the simulation of 3D kinematics of the spine in vivo, but the efficiency and accuracy of this technique need further evaluation.

[Stress distribution on the femoral neck at different abduction angles of the hip joint: a finite element analysis].

OBJECTIVE: To analyze the stress distribution and its changes of the femoral neck at different abduction angles of the hip joint to provide biomechanical evidence for the treatment of hip joint disease. METHODS: A three-dimensional finite element model of the femoral head region was reconstructed on the basis of data available in the dataset of No.1 Virtual Male Chinese. Different abduction angles of the hip joint were simulated under the load of body weight, and the stress distribution on the femoral neck was calculated and compared. RESULTS: With different abduction angles of the hip joint, the stresses on the medial and lateral sides of the femoral neck were obviously greater than those on the anterior and posterior regions. As the abduction angle of the hip joint increased, the stress on the posterior aspect of the femoral neck decreased while that in other regions increased (except for the anterior aspect of the femoral neck which remained unchanged). CONCLUSION: The lateral aspect of the femoral neck withstands the most intense stress of the body weight, which increases with the abduction angle of the hip joint.

[3D image analysis of nasal orbit fossa through a laser scanner: a new method and application of 3D image].

OBJECTIVE: This study was to introduce the method for obtaining accurate 3D data of soft tissues using a 3D scanner under non-contact condition and the standard 3D measurement of the nasal orbit fossa for plastic surgery. METHODS: A 3D laser scanner and the Geomagic software were used to obtain the standard facial contour of 30 Chinese people. The nasal orbit fossa, as the feature of beauty, was measured and the data were analyzed. RESULTS: 3D measurement exhibited the three-dimensional facial shape at every meaningful angle, with the advantages of high precision of 0.01 mm. We determined the lowest point and described the 3D feature of the nasal orbit fossa. CONCLUSIONS: This method can illustrate the relation of the nasal orbit fossa and the surrounding structure. It is a new approach to facilitate preoperative plans, operation simulation and postoperative evaluation.

[Reconstruction of the mandibular model using a three-dimensional laser scanner].

OBJECTIVE: To construct a three-dimensional (3D) mandibular model using a 3D laser scanner, and explore a new method for reconstructing the finite element geometry model. METHODS: A mandible specimen was scanned with the 3D laser scanner to form the point clouds of the mandibular surface, which were subsequently aligned for reconstruction of the mandibular model. RESULT: A 3D model of the mandible surface was reconstructed, which could be used for finite element simulation. CONCLUSION: The 3D laser scanning system can be used to reconstruct the 3D model with irregular geometry for finite element simulation.

[Comparative study of vertebral body stress distribution following insertion of artificial lumbar intervertebral disc].

OBJECTIVE: To study vertebral body stress distribution of normal disc, post-Diskectomy and artificial disk respectively by 3-D finite element methods, and to explore artificial intervertebral disk insertion impact on stress distribution of vertebral body. METHODS: Models of normal disk, post-Diskectomy, artificial disk and L(4 - 5) motion segment were established by using finite element software MSC. MARK, then vertebral body stress was analyzed through model of L(4 - 5) motion segment respectively. RESULTS: The vertebral body's stress was the smallest after insertion of artificial intervertebral disk (AID), and its stress distributed equally. But the stress under post-discectomy was bigger than the normal disc's in all the motion state. On the other hand, the stress distribution state of the post-discectomy changed while the spine were in different motion state, during the spine flexion, the stress in the anterior of vertebral body was the biggest; While extension, in the posterior and in right flexion state, the biggest stress was in the right. While vertical compression and rotation, the stress distributed equally. CONCLUSION: The results illustrate that the vertebral body's stress is the smallest after insertion of AID in 3 groups of all motion state, and its stress distributes equally. But the level of vertebral body stress increases after discectomy comparing with the normal group. In generally, it is much more reasonable that the disc is reconstructed with AID because of the biomechanical effect on vertebral body made by AID insertion.