| Objective The comminuted fracture of the femoral shaft fixed by long locking plate can increase the working length of the locking plate and effectively disperse the stress of the locking plate.For the simple fracture of the femoral shaft,the working length of the locking plate on the biomechanical distribution and the healing of the fracture are still controversial,the relevant biomechanical studies are rare.If the working length of the plate is short,the stress of plate is too concentrated,increasing the risk of failure of the internal fixation.If the working length of the locking plate is increased or the fracture space is too large,the strain of fracture will be too large and affect the process of fracture healing in osteoblast differentiation and bone formation,which may increase bone delayed union or nonunion risk.The ideal working length of the locking plate can effectively reduce the incidence of postoperative complications and improve the clinical efficacy.Method Thirty artificial femur simple fracture models of femoral shaft were constructed.The models were randomly divided into three groups,including A group,B group and C group with 10 specimens in each group.A group was fixed with locking nails,the fracture gap was 2mm;B group near the fracture was fixed with two compression screw to slide compression.Then four locking screws were fixed in other screw holes;group C empty one hole at eath end of the fracture,then two compression screws were fixed with slide compression.Besides,four locking screws were fixed in other screw holes.Axial compression,three-point bending and dynamic fatigue experiment were proceeded for each specimen before experiment to explore the feasibility of the experiment scheme,and to determine the axial compression,three-point bending and dynamic fatigue experiment yield point,ultimate strength and the tolerable maximum load of the specimen.Axial compression experiment,three-point bending experiment were accomplished in different load downward,measuring and recording the strain of different points.Besides,bending resistance and dynamic fatigue experiment were accomplished in different load downward,then the relevant data for statistical analysis.Research locking plate working length and fracture gap on the distribution of the biomechanics of fracture of femoral shaft.Result The strain of point5 and the point6 of group A,group B and group C under different compression loads(600N,1400 N,1800N)were different,and the difference was statistically significant.Fracture site strain size: group A>group C>group B.In group A,the strain of point5 under different compression loads was between 2-7%;the strain of point6 under 600 N of compression loading was between 2-10%,under 1400 N and 1800 N were between 11-16%.In group B,the strain of point5 and point6 under 600 N of compression loading strain were less than 2%;under 1400 N and 1800 N of compression loadings were between 2-10%.In group C,the strain of point5 under different compression loads was between 2-10%;the strain of point6 under 600 N and 1400 N of compression loadings was between 2-10%;under 1800 N compression loading was greater than 10%.Under 1800 N axial compression loading,plate local micro strain size: group A > group C > group B,and the difference was statistically significant.The strains of point5 and point6 of group A and group B under different bending loads of 300 N,600N and 900 N were between 1-9%.In group C,the strain of point5 under 300 N bending load was between 2-5%;under 600 N bending load was between 7-11%;under 900 N bending load was between 11-18%.In group A,group B and group C,when the bending load was less than 770 N,the strain size of point5 and point6 were group C>group A>group B;when the bending load was greater than 770 N,the strain size of point5 and point6 were group C>group B>group A.The local micro strain of locking plate under 600 N bending load: group A was about(410.16-621.16)με;group B was about(453.21-722.61)με;group C was about(375.16-621.36)με.The experimental results of resistance to bending performance as follows: group A maximal displacement was(35.54±0.59)mm;group B maximal displacement was(42.56±0.48)mm;group C maximal displacement was(36.74±0.45)mm,the difference was statistically significant.When the specimen reached to maximum displacement,the bending load size as follows: group A was(1273.53±1.86)N;group B was(1185.57±1.24)N;group C was(1115.57±1.48)N,no plate or screw breakage occurred.In dynamic fatigue experiment,when the compressive load was 600 N,no plate or screw breakage appeared in group A;when the compressive load was 1400 N,two specimens were failured in group A: one specimen was failured in 350 thousand cycle,the other specimen was failured in 400 thousand cycle;when the compressive load was 1800 N,three specimens were failured in group A,one specimen was failured in 200 thousand cycle,two specimens were failured in 210 thousand cycle.No internal fixation failure occurred in group A,group B and group C under different dynamic loads.Conclusion Locking compression plate for the treatment of femoral shaft fracture,when empty one hole at eath end of the fracture can increase the working length,but the strain of fracture area was larger than 10% at the advanced stage of fracture healing,patients should use walking aids to auxiliary function exercise and appropriately reduce the strain of fracture site.The risk of fatigue breakage of plate or screw was increased when the fracture space was 2mm.So simple femoral shaft fracture should be fixed using hybrid fixation principle.Firstly,two compression screws were fixed in order to slide compression near the fracture to eliminate fracture space.Then,remained nails were fixed.The patient was encouraged early ambulation and late weight-bearing functional exercise,which could stimulate the formation of bone cells,promote bone fracture healing and improve the clinical efficacy. |
PDF Full Text Request