ObjectiveTo evaluate biomechanical properties of transoralpharyngeal atlantoaxial reduction plate (TARP) prepared from magnesium alloy and titanium alloy for the atlantoaxial dislocation by using three-dimensional finite element analysis and to exam the feasibility of using magnesium alloy for preparation of TARP system so as to provide a theoretical basis for clinical surgery.MethodsA patient with typical atlantoaxial fracture dislocation was involved in the study,and received thin CT scan with clinically used titanium alloy TARP system for obtaining DICOM image data.Three-dimensional finite element analysis software was imported to simulate magnesium alloy and titanium alloy TARP systems for reduction and fixation.Then,stress changes of the atlas,axis,internal fixators and C2/3 zygapophysial joints were determined with three-dimensional finite element analysis and analyzed statistically.Results ( 1 ) The finite element model of atlantoaxial dislocation reduction and fixation had lifelike outline and good geometric similarity.There were 53 586 nodes and 180 784 units.(2) During the simulation of head in neutral position,the stress concentration region was C2/3 zygapophysial joints followed by the anterior arch,posterior arch and lateral mass of atlas respectively,and C2 vertebral arch again.( 3 )Magnesium alloy and titanium alloy TARP systems showed significant difference in stress distribution (P ＜0.05).Conclusions(1)The atlantoaxial model established according to its structure information on CT can be used for biomechanical experiments.(2) For the treatment of atlantoaxial dislocation using the existing titanium TARP system,maintaining the integrity of anterior and posterior arch of atlas and confirming the bone fusion in lateral mass can better keep the stability of the atlantoaxis.After atlantoaxial fusion,the increased stress of the zygapophysial joints of the adjacent segments accelerates structural degeneration,which should be closely followed up.( 3 ) Magnesium alloy TARP system for fixation and reduction shows the fall in peak value of the stress concentration region,and improvement of the uniformity of stress distribution as compared with titanium alloy TARP.

OBJECTIVETo explore the effect of different functional groups on self-assembled monolayers on the biological characteristics of rabbit skeletal muscle cells in vitro.

METHODSRabbit skeletal muscle cells were cultured on self-assembled monolayers of gold on which different terminal chemical groups including methyl groups (-CH(3)), amino(-NH(2)), hydroxyl(-OH) and carboxyl (-COOH ) were anchored with self-assembled methods. Contact angle measurements and atomic force microscopy were employed to confirm the similar density of different functional groups occupation. Fluorescence microscopy, MTT assay, flow cytometry, and scanning electron microscopy (SEM) were used to analyze the morphological and biological alterations of the cells.

RESULTSSEM results revealed that the chemical groups on the surface of the monolayer modulated the structure of skeletal muscle cells and the cell morphology. Skeletal muscle cells cultured on the monolayer with -CH3 exhibited the smallest contact area with a spherical morphology, while the cells on the monolayers with -NH(2), -OH and -COOH showed much larger contact area and flatter morphology. The functional groups -NH(2) and -COOH obviously promoted cell adhesion and proliferation, while -CH(3) group produced significantly greater toxicity than -NH(2), -OH and -COOH groups to inhibit the cell growth and adhesion and promote cell death. Cell attachment and growth was enhanced, in the order the magnitude of the effect, by -NH(2)>-COOH>-OH>-CH(3), and the toxicity decreased in the order of -NH(2)>-COOH>-OH>-CH(3).

CONCLUSIONThe terminal chemical groups can obviously affect the phenotype of skeletal muscle cells in vitro, and this finding provides a theoretical basis for surface design of biomaterials.

Animals ; Cell Adhesion ; Cell Proliferation ; Cells, Cultured ; Microscopy, Atomic Force ; Microscopy, Electron, Scanning ; Microscopy, Fluorescence ; Muscle Fibers, Skeletal ; cytology ; Rabbits