| BackgroundFracture wire internal fixation is the earliest fracture fixation technique ever recorded by humans.The first case was recorded more than 2 centuries ago.The steel wire internal fixation technology is simple in operation,reliable in fracture fixation,and cheap and easy to obtain materials.It does not require the use of special instruments for surgery,and is flexible,convenient,economical,and easy to use.It is suitable for medical institutions at all levels.Wire fixation is a widely-used fixation technique especially in areas such as hand-foot surgery,bone surgery,spine and joints surgery,oral and maxillofacial surgery,orthopedic surgery,and cardiothoracic surgery that need to deal with fractures Although there have been improvements in steel wire intrafixation technique and people have also invented related medical devices for tightening the wire.In general,the operation mode of the wire fixation surgery still maintains a relatively primitive situation.That is,first accurately align the two ends of the fracture,guide the medical wire through appropriate positions on both ends of the fracture,and then use a wire needle holder(or vise,etc.)to Clip the ends of the wires that have passed around the bundled bone and then perform the "twist-like tightening" procedure to tighten and lock the wire and perform the fixation of the fracture.In traditional wire fixation surgery,the number of tightening turns is completely dependent on the doctor's experience,and there is a certain degree of uncertainty.In a certain clinical situation,if the number of laps is too small,sufficient tightening force cannot be provided and the stability of the fixed system cannot be satisfied;if the number of laps is too large,the tightening force of the steel wire is too large,and it is easy to occur during surgery or Wire breakage after operation,or the embedding of the steel wire in the cortical bone,may affect healing or cause other postoperative complications.When severe,it may move to nearby vital organs and may even endanger life.Objective 1)Explore the factors affecting the needed number of turns of the medical stainless steel wire,recognize the master-subordinate relationship of these factors;2)Establish and analyze idealized wire tightening mathematical model,fully understand the essential laws of the wire tightening process,and deduct the theoretical calculation formula of appropriate number of turns of the wire;3)Through the simulation experiment of steel wire internal fixation in vitro,establish an empirical relationship between the factors influencing the number of twisting turns of the steel wire and the actual number of turns,and an empirical formula for calculating the number of safe tightening turns.Method1.Detect the factors of the number of "twisting-off" of the internal fixation wire through Control variable method.Perform wire fixation experiments with fresh phalanx,metacarpal and ulnar specimens in vitro.Set the perimeter of bundled bones as c,the initial length of the twisted portion of the steel wire as l0,and the outward pull force as F.Set one of these three factors as independent variables and the other two factors as the control variables and the number of wire loops(nb)as the dependent variable.Perform experiments one by one,studying the effect of three factors on the number of twisting turns of the steel wire.2.Establish an idealized "tightening" model of steel wire to derive the theoretical calculation formula for the number of turns that leads to twisting-off.Based on the characteristics of internal fixation of steel wire and the simple cerclage,an idealized mathematical "tightening" model containing the parameters of bone circumference and mechanical properties of steel wire is established,which can deduct and simplify the formula for calculating the number of "twisting off" turns when combined with the internal fixation process of the fracture wire and the characteristics of force and deformation during the tightening process,and the geometric characteristics of the spiral screwing.3.Fitting of the empirical formula of the number of safe tightening cycles of the inner fixation wire 1)Perform experiments in fresh phalanx,metacarpal and ulnar specimens in vitro.Orthogonal experimental design is used instead of comprehensive experiment to explore the master-subordinate relationship of three factors—the circumference of the bundled bone,the initial length of the twisted part of the steel wire,and the outward pull force of the wire tightening operation.relationship.2)In fresh phalanges,metacarpal bones and ulna specimens,simulate wire fixation in vitro and collect independent variable values and the corresponding number of unscrewing cycles nb,to determine the factors affecting the number of wire twisting cycles nb,with a 99%confidence interval minimum,which leads to the empirical formula for calculating the number of safe tightening cycles ns.Result1.Detect the factors of the number of "twisting-off" of the internal fixation wire through Control variable method.1)he circumference of the bound bone c affects the number of turns of the wire:Levene test for homogeneity of variance p>0.05(p=0.079)One-way analysis of variance(ANOVA)F=1.294,p>0.05(p=0.285).There was no significant difference between the four groups of statistical tests.2)Pulling force F along the spiral axis of the wire during tightening affects the number of "twisted"turns:Levene's homogeneity of variance test p<0.05(p=0.214),One-way ANOVA F=1.294,p<0.05(p=0.007),4 sets of test results have statistically significant differences.3)The initial length of the torsion part l0 affects the number of "twisting-off" turns:Levene variance homogeneity test analysis The variance of the four groups of experimental data grouped by the initial length of the torsion part l0 is homogeneous,p<0.05(p=0.031),Tamhane's T2 There were p<0.05(p=0.000)among the multiple comparison groups.The statistical difference among the four groups was extremely significant.2.Ideal model and theoretical formula An idealized wire tightening model was established,and the theoretical calculation formula for the tightening number of wire wasdeduced:(?):? is equal to elongation after breaking A,n=nb);3.Orthogonal tests and empirical formulas 1)Visual analysis of orthogonal experimental results shows that the factor C(bone circumference)is 1.04 for the R and 0.79 for the factor F(axial force in the tightening).The R of l0(the initial length of the torsion part)is 18.335;the order of the factor effect is:factor l0>factor c>factor F;2)Analysis of variance of orthogonal experiment results:bone circumference The long(c)F value was 2.44,p>0.05(p=0.08);the F value of the pull force(F)was 1.32,p>0.05(p=0.28);the F value of the twisted length(l0)was 508.91,p<0.05(p=0.00);3)Fit the number of safe tightening cycles of the inner fixed wire ns empirical formula:ns=l0-2,(R2=0.9994),l0.units are millimeters(mm),ns units are circles.Conclusions 1)Among the three factors influencing the "twisting" of the steel wire,the length l0 of the torsion part plays a decisive role in the number of twists nb.While the circumference c and the the pulling force F along the axial direction of the spiral has no significant effect on the number of twisting turns nb;2)Based on the "idealized" wire tightening model and the mechanical properties of steel wire materials,the formula for calculating the number of turns of the internal fixed wire is deduced:n =(?),?is equal to elongation after breaking A,n= nb).But it is far from the in vitro test and can not meet the clinical application.3)Medical stainless steel wire used in this experiment is:?0.3mm,produced by Shanghai Jinzhong.It is commonly used in hand and foot surgery in Shandong Provincial Hospital to perform fracture fixation within a certain range.The number of safe tightening turns of the inner fixed wire is empirical formula:ns=l0-2,l0 units are millimeters(mm),ns units are circles.This formula is intended for clinicians in manipulation of metacarpal phalanges and similar sites during wire fixation. |
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