The Biomechanical Impact Of Pressure Changes Of Metacarpop-halangeal Joint In Daily Activity After Internal Fixation Surger-y Of The Fifth Metacarpal Neck

Objective:Establish multiple normal human fifth metacarpal neck fracture models and differrent internal fixation models,To observe the fifth metacarpal necks, biomechanics changes in different models under the metacarpophalangeal joint, pressure of daily activities, and to explore its regularity.Methods:Selecting a total of10cases of young men and women matching normal filter condition,making CT scaning on the research area for each one and model reconstruction by using Three-dimensional finite element softwares.Testing the models comparing body bones. After Satisfaction of the testing,making biomechanical analysis of all sorts of models in physiological conditions or in fracture state with internal fixation. Entering the observed data into statistical software named SPSS13.0for statistical analysis.Result:Ladder diagram:The displacement value of normal fifth metacarpal neck group increasing from0.0078cm to0.0541cm.The trend chart is similar to a line.The Pressure value increases from0.340KP to0.340KP, The trend chart is similar to the logarithmic graph. Pressure changes quickly between40N to80N.The displacement of group which fifth metacarpal neck fracture fixxing by steel plate increased from0.0068cm to0.0556cm. Gradient map is approximate linear.The pressure value changes from0.220KP to1.0KP, Gradient map is approximate linear. The displacement of gram needle group increases from0.0092cm to0.1063cm,. presenting a linear growth trend.The pressure values changes from0.380Kp to3.190KP, present a logarithmic growth trend.The intramedullary needle group, displacement values increase from0.0591cm to0.1564cm, presenting a linear growth trend.Pressure values changes from0.402Kp to3.210KP, present a logarithmic growth trend.At different stress stages, The metacarpal neck pressure values of intramedullary needle group are greater than the normal.And comparing with the normal,the difference is not constant, presenting a growth trend. Analysis of Variance:The results of the Comparison of different group shows that: there was no significant statistical difference between steel group and normal group. Compared with normal group, needle group shows differences under the pressure of50N,80N,90N,100N. there is statistically significant, p<0.05. Intramedullary needle group are statistically significant with normal group,p<0.05. But the biggest displacement of each one is less than1/3of the cross-section.In the comparison of neck,pressure between different groups,there are significant differences between steel group and normal group in the pressure(30N to100N),p<0.05.but there are no significant differences between normal group and intramedullary needle group or gram needle group.Conclusion:1The displacement of metacarpal neck, section are in the acceptable range in the three groups.The result can meet the basic needs of clinical.2The pressure change trend of steel plate group is linear.There is a obvious difference comparing the normal.The statistical analysis has prove the poin-t.However,The gram needle group and intramedullary needle group havs no significant difference comparing the normal.It isvaluable and significant to rebulid the mechanical Features.3According to the theory of micro-movernent,0.5hz,1-2mm micro-move can stimulate callus growth, Intramedullary pin group can maintain the displacement of1mm or so in the whole process,itcan stimulate teh growth in theory.And the needle group only can form the stimulus under80N pressure,but the displacement of the steel plate group is about0.5mm in max.It is hard to form effective stimulus.4Above all,the intramedullary pin internal fixation method is an effective way,but this is just for oblique fracture analysis.There will be a further need to analysis of the other fractures.