Objective:To develop and validate an accurate three-dimensional geometrical and mechanical finite element(FE)model of the lumbar L_(4)-L_(5) segment using a new computer-aided designing(CAD) method.Methods: First,a modified "non-seed region segmentation" was done to extract the interest region in the CT image and to obtain a binary image,from which the iso-surface of vertebral body was produced by a discretized marching cubes algorithm.Second,"best cross-section planes" representing the morphologic characteristics of physiological lordosis were used for the initial iso-surface model,forming a "non-regular piecewise subspace".This subspace and the embedded iso-surface model were subsequently transformed by local affine transforms to a "regular subspace",in which a surface mesh of high quality was generated quickly.Finally,a reverse transform procedure was employed to restore the original three-dimensional(3D) image of the lumbar surface mesh of lumbar L_(4)-L_(5).All coordinate dada of nodal points and message of triangular patches of the surface model were then subjected to ANSYS for the three-dimensional FE mesh construction.An accurate 3D non-linear FE model of lumbar motion segment(L_(4)-L_(5)) was developed and validated against published data.Results: The constructed FE model of lumbar L_(4)-L_(5) consisted of 94 794 solid elements,1 196 link elements,1 170 shell elements,768 target elements and 464 contact elements,and included geometrical,material and contact non-linearities.The predicted results of lumbar L_(4)-L_(5) segment were closely correlated with published results of experimental biomechanics in terms of axial displacement,segment rotation and intradiscal pressure under similar load condition.Conclusion: Based on advanced algorithm,this constructed surface model of L_(4)-L_(5) segment is capable to perform whole digitalized binary image extraction and reconstruction of the lumbar surface with excellent simulation results.

20 mm) and short variation(≤20 mm).The average follow-up time was 32 months(range 24 to 48).Spinal function was evaluated by JOA(Japanese Orthopaedic Association) guidance at hospital admission and at the follow-up time of 24th month,and neurological improvement was expressed by the recovery rate.[Result]At the follow-up review of 24th month,the neurological improvement according to the recovery rate of the early surgical treatment group was higher than late surgical treatment group(P

Recently, stem cells attract significant attention in cartilage tissue engineering as an alternative to autologous chondrocytes. Bone marrow-derived stem cells showed potency to chondrogenesis in various culture conditions. Adipose-derived stem cells are a kind of fibroblast-like stem cells population which can be isolated from adipose tissue and cultured in vitro, can differentiate into chondrocyte after an extended period with stable expansion and low levels of senescence in 3D culture environment. Besides bone marrow and adipose tissue, muscle, synovium, and periosteum are other sources of adult stem cells being explored for applications in cartilage repairment. Furthermore, co-culture of human embryonic stem cells with primary chondrocytes can induce the chondrogenesis differentiation, however, the difficulties in ESC selective purification, as well as oncogenicity and ethical issues, may limited the use in clinic.

Articular chondrocytes are the main cell sources for cartilage repair.However,the harvesting of articular cartilage is a highly invasive procedure accompanied by the potential site morbidity and loss of function for donor.In addition,low cell yields,low mitotic rates,and low bioactivity further limit the use of articular chondrocytes in clinic.Other potential autologous chondrocyte sources in vivo include auricular,nasoseptal and costal cartilage with differences function,structure,and composition which result in different discrete biochemical,physical and biomechanical properties.Presently,efforts in cartilage regeneration mainly focus on chondrocytes isolated from immature animals,which have faster growth rate and rapid capacity for differentiation than those from old donors.Skin presents a minimally invasive,relatively abundant source of fibroblasts for tissue engineering.Although the direct transplantation of fibroblasts on PLA meshes in a cartilage defect may leads to fibroplasia,fibroblasts can be induced differentiated into chondrogenic phenotype under the appropriate culture conditions.

[Objective] The efleet of sagittal orientations of articular facet on the contact force and contact regions of a lumbar spine segment was evaluated.[Methods] [Results]Three-dimensional geometrical and mechanical accurate finite element models of the lumbar L4、5 motion segment representing three sagittal-orientations articular facet were generated and invalidated by an effective CAD method.Contact force and contact regions of the articular facets of three finite element models were predicted under the pure shearing loads.[Result] Under anterior shear condition,the contact force on the facet decreased with the increase of sagittal 0rientation of articular facet.however.in posterior shear load,the contact force on the facet increased with the increase of sagittal orientation.Meanwhile,under both pure shear loading,the percentages of the sagittal and the transversal components are increased with the dectease of the sagittal angle.However,under the salne load condition,there are no difference between the contact regions of the three models with different facet joint angle.[Conclusion]The spatial orientation and geometric forms of the coronal facet articular surfaces are more effective in restricting motion in transversal and sagittal planes while assuming a minor role in resisting axial force or motion than sagittal facet articular surface.It Was presumed that anterior shear force play a more prominent contribution on the degeneration of the facet joint with coronal articular surface compared with posterior shear force.

BACKGROUND: Histomorphological change of endplate may affect the nntritional transmission of intervertebral disk, eventually leading to intervertebral disc degeneration. OBJECTIVE: To observe the effects of endplate concavity variation on mechanical response of lumbar motion segment. DESIGN, TIME AND SETTING: Repeated measurement design, biomechanical analysis of finite element models, performed at the Laboratory of Biomechanics, Department of Orthopedics, the Second Affiliated Hospital of Medical College of Zhejiang University between January 2005 and January 2007. MATERIALS: SOMATOM SENSATION 16 spiral CT machine (Siemens, German) and ANSYS (Inc. Pennsylvania, USA).METHODS: A three-dimensional nonlinear geometrical and mechanical accurate finite element model of lumbar L<,4-5> segment was developed. Parametric studies were undertaken by studying endplate of three different concave angles, whereas disc angle, the gap of facet joint, finite element mesh density, and all other parameters were kept constant. Biomechanical parameters of three kinds of finite element models were tested under 5 different loading conditions, including vertical compression, flexion, extension, and anterior and posterior shearing loading. MAIN OUTCOME MEASURES: Endplate-intervertebral disc interface strain, intervertebral disc stiffness, nucleus pulposus pressure, annular fiber stress, radial disc bulge, stress in the annulus ground substance, stresses in posterior structure and facet contact force. RESULTS: The decrease in the endplate concavity stimulated by an increasing endplate concave angle would result in decreased strains of endplate-intervertebral disc interface, increased disc stiffness and nucleus pulposus pressure, decreased annular fiber stress, radial disc bulge and stress in the annulus ground substance, and simultaneously produce decreased facet contact force and stresses in posterior structure. CONCLUSION: The decrease of endplate concavity enhances the protective effects of the disc on vertebral body breakage. Small endplate deformation results from decreased endplate concavity would contribute to the reduction of nutritional diffusion to the intervertebral disc.

Tumor cells can secrete various cytokines which can enhance the activity of osteoclast in the bone microenvi?ronment, and osteoclast can promote the release of many growth factors buried in bone matrix which would promote the growth and invasion of tumor cells. Thus, a‘vicious cycle’of bone destruction is developed in the bone metastatic microenvironment. Bone metastatic microenvironment facilitate this‘vicious cycle’, while it also provides potential targets for the treatment of bone metas?tases. Osteoprotegerin, receptor activator of nuclear factor?κB and its ligand system are the typicality of molecular targets. Bone metastasis can promote the secretion of RANKL and the expression of OPG. The disbalance of RANKL/OPG is an important induc?ing factor for bone destruction. Many studies have shown that transforming growth factor?βwhich is produced by osteoclast plays an important role in mediating‘vicious cycle’. Src family tyrosine kinase, endothelin A receptor, matrix metalloproteinase, and ca?thepsin K are the potential targets of bone metastasis. Pharmacologic agents such as denosumab, can inhibit the‘vicious cycle’of bone metastasis. In addition to suppress bone destruction by Pharmacologic agents, they also can produce direct antitumor effect. They can delay the occurrence of skeletal related events, prolong the overall survival, and play an important role in patient ’s quali?ty of life at last. Patients with bone metastasis have already benefited from systemic molecular targeted therapies, and further re?searches would be of great importance in improving patient therapeutically selections and enhancing the effect.

The incidence of spine metastasis is increasing due to the aging demography and improvement of cancer diagnosis and treatments.Spine metastasis is one of the serious complications of advanced cancers,and its treatment should pay attention to patients' quality of life and consider interdisciplinary cooperation.Expected life span can guide doctors to select the appropriate treatment for spine metastasis patients,and various scoring systems have been developed.We elicited relevant literatures in WanFang,CNKI,PubMed and Embase databases.Articles aiming at developing model for spine metastasis or describing the clinical effectiveness and pitfalls of the existed systems were included.As a result,48 articles were carefully reviewed.In this review,thosc scoring systems were stratified into two groups:Traditional scoring systems,which were published before or in 2005,including original/revised Tokuhashi scoring systems,Tomita scoring system,Bauer scoring system,Linden scoring system,and Sioutos scoring system;and new scoring systems,which were designed during the last three years,including Lei & Liu scoring system,Bollen scoring system,Rades scoring system,Oswestry spinal risk index (OSRI),and Katagiri scoring system.The usefulness of the traditional scoring systems has been validated by many studies.However,the applicability of those scoring system were controversial due to improvement of cancer treatment and survival period in recent years.Although the improvement of life span was considered,those new scoring systems have not penetrated into clinical routine because of the lack of validation.Currently,which system has the highest accuracy rates still remains unclear.Next generation of scoring systems should take into account the practicality and reliability at the same time.In this review,we introduced above mentioned scoring systems,described the validity and limitation of those scoring system,and suggested the future directions of next generation of scoring systems.

BACKGROUND:Core decompression and tantalum rod implantation after core decompression are common methods to repair early and middle stages of necrosis of femoral head, can effectively control and even reverse the progress of necrosis of the femoral head. Comparison of mechanical support and curative effect of femoral head after operation deserves further investigation. OBJECTIVE:To explore the effect of core decompression on mechanical pulp femoral head support by using the finite element analysis and the advantages of tantalum implant treatment in the repair of avascular necrosis of the femoral head. METHODS: The right femur of healthy adults was chosen as the research object, and CT scanning was conducted to get the images of cross-sections. The images were then inputted into computer to get contour of femur and rebuild three-dimensional model. Distal end of femur was completely fixed, the angle of the top of femoral head and the femoral shaft was 25°, and 570 N pressure on the femoral head was applied according to the three-dimensional space distribution of femur force under physiological state. Three-dimensional finite element models were calculated to get the colapse values in different necrotic areas of the femoral head before and after different repair methods. RESULTS AND CONCLUSION:After core decompression, colapse values were apparently increased, especialy in the weight-bearing area. With increased range of necrosis, colapse values also increased. After core decompression, colapse values decreased obviously after porous tantalum rod implantation. Although core decompression could remove dead bone, decompression itself further reduced the mechanical properties of the femoral head and changed the original femoral head support. On the basis of core decompression, porous tantalum rod provided safe and effective mechanical support for femoral head and subchondral bone plate, could effectively prevent colapse and provide conditions for the restoration of bone tissue.

Scaffolds provide a three-dimensional environment that is desirable for inducing and promoting the production of cartilaginous tissue.Ideally the scaffold should:① have directed and controlled degradation;② promote cell viability,differentiation,and extracellular matrix production;③ adhere and integrate with the surrounding native cartilage;④ span and assume the size of the defect;⑤ provide mechanical integrity depending on the defect location;⑥ have no toxicity,no immunogenicity or inflammatory induction;⑦ allow for the diffusion of nutrients and waste products.To date,a wide range of natural and synthetic materials have been investigated as a scaffold for cartilage repair.Based on the morphology and structure,these materials can be divided into hydrogel,sponge,fiber mesh and so on.Natural polymers that have been explored as bioactive scaffolds for cartilage engineering include:alginate,agarose,fibrin,hyaluronic acid,collagen,gelatin,chitosan,chondroitin sulfate,and cellulose.Synthetic polymers currently explored for cartilage repair include poly(?-hydroxy esters),polyethylene glycol,poly(NiPAAm),poly(propylene fumarates),and polyurethanes.