| Objective:In this study,the finite element method was used to build a three-dimensional finite element model of Pauwels typeⅲfemoral neck fracture with different internal fixation methods,and the validity of the model was verified to confirm that the model was scientific and effective,and it also provided a basis for its application in other studies.According to the displacement of femoral head,the stress distribution of screws and plates was compared and analyzed,which provided theoretical guidance for choosing the best internal fixation method in clinical treatment of Pauwels typeⅲfemoral neck fracture.Finally,taking the results of clinical research as the core,the specific treatment of the two kinds of internal fixation was analyzed.Methods:Construct a perfect three-dimensional model for the proximal femur.In this research,the core research object is healthy young talents.When scanning their proximal femur,the scanning tool is 64-slice spiral CT.In the scanning phase,the thickness of layers is set to0.625mm,the interval between layers is set to 0.625mm,and the pixel is set to 512×512.The whole hip joint is scanned from bottom to top from the lower lumbar spine of volunteers.After scanning,569 tomographic image sequences in DICOM(Digital Imaging and Communications in Medicine)format are obtained.Save the original data obtained from proximal femur,and then transfer the data to Mimics15.0 software.At the same time,with the help of this software,the gray-scale images of bones and restored images of flesh and blood are drawn.In order to improve the resolution or smoothness of the whole image,it is necessary to carry out preprocessing operations.Compared with the density of bone tissue,the femoral tissue is quite different from it.When extracting this data,we should follow the principle of gray value.In addition,when optimizing the influence quality in the tissue,we need to use the filling function and sub-extraction function in the software.With the help of the software,we can get the most perfect rough model of bone tissue,and save the model with the help of STL file.Then,the file is transferred to Geomagic and Pro/Engineer(Proe)PROE software,and smoothing and surface fitting are implemented by these two softwares.Through the above operation steps,a perfect 3D solid model of femur is finally obtained,which is ready for subsequent operation model processing and finite element analysis.2.The screws used in this experiment are mainly AO hollow compression type screws and inner compression steel plates(plastic tubular steel plates),which are widely used in clinic.Three-dimensional laser scanning technology is used to reverse model the screws and steel plates to prepare for the assembly of internal fixation models.3.The model was divided into two groups according to different fixation methods.group a was fixed with three hollow nails in inverted"pin"shape,while group b was fixed with three screws and anterior medial plate,and the fixation shape was"pin"shape.firstly,pauwels typeⅲfemoral neck fracture model was established in Proe2.0PROE software,and the models were assembled according to the fixation methods of group a and group B..4.Build a perfect finite element model for the proximal femur,and analyze the model.After the model is built,it is transmitted to Ansys 13.0 software,and then the finite element analysis of the model is carried out with the help of this software.In the analysis,the unit mainly used by the two groups of models is"Solid 187 Unit",which is used to mesh the fracture model and proximal femur effectively.In this process,it is worth noting that special parts must be refined when meshing,whether it is screws,drumhead and steel plate,etc.In addition,the nodes at the lower end of femur are processed to ensure that the parameters set at the top of femoral head can load the coupling points.The maximum force of the loading link is set to 600N.After the loading operation is completed,the loading situation is transmitted to Ansys system,and the static calculation operation is carried out by using this system.Observation indexes mainly include(1)stress distribution and peak value of femoral head;(2)Stress distribution and peak value of screws and internal fixation steel plates;(3)Displacement of screws;(4)Displacement of fracture.5.In clinical study,60 patients with PauwelsⅢtypeⅲwho were treated in the Department of Orthopaedics of our hospital from February 2017 to February 2020 were selected for study.All the patients included in the study showed obvious high-energy injuries(falls,car accidents,etc.),and were confirmed by X-ray film and CT.Among them,there were 36 male patients and 24 female patients,aged between 25 and 60 years,with an average age of(40.45 11.89)years.Among them,there were 23 road traffic injuries,13 high fall injuries,and 24 flat falls and sprains.According to the random number table,the patients were divided into two groups:group A(3 hollow nails inverted"Pin")and group B(3 hollow nails inverted"Pin"+anterior medial plate).The indexes of patients’operation were compared and analyzed,such as Harris score.Such as operation time or postoperative healing,etc.Result:1.Finite element analysis resultsCompared with the classical literature,the compression stiffness of the model under1500N compression load is analyzed,and it is confirmed that the model established in this experiment is effective.Through calculation and analysis,it is found that the peak displacement of group A can reach 2.06mm;when walking slowly.In the whole process,the peak displacement of femoral shaft is 1.40mm;Peak displacement of femoral head is2.06mm;The peak value of screw is 1.89mm;The peak value of femoral neck was1.56mm;As far as torsional movement is concerned,when the experimenter is exercising,the maximum displacement is 1.43;Among them,the peak displacement of one-legged standing link can reach 2.12 at the highest.In addition,during the experiment in group B,the experimenter walked slowly,and the peak value of the whole displacement reached1.97mm;The peak value of femoral shaft displacement can reach 1.36.The maximum displacement peak of femoral head and screw can reach 1.97mm and 1.82mm;respectively.The highest peak displacement of femoral neck can reach 1.51mm;The maximum displacement peak of steel plate can reach 1.29mm;The maximum displacement peak value can reach 1.43mm;during torsional movement.Among them,the highest displacement peak can reach 2.05mm when standing on one leg.After analyzing the cloud map of displacement distribution,it is known that the maximum displacement is mainly distributed at the highest position in the model.For example,the whole model is distributed on the femoral head,which is because the load is vertically loaded on the model during analysis.When walking slowly,the maximum displacement of group B model is 14.7%lower than that of group A model.The other two kinds of exercise,because the load is very small,the patient can carry out the corresponding exercise within the bearing range after the operation.Therefore,there is no difference in the displacement between the screw and the femoral head,or the femoral neck and the steel plate when the patient performs these two kinds of load exercises.When walking slowly,the highest stress peak of model A can reach 318.09Mpa,while the highest stress peak of femoral shaft can reach 55.92Mpa.The highest stress peak of femoral head can reach 11.54MPa.The maximum stress peak of the screw can reach 318.09MPa;The highest stress peak of femoral neck can reach 20.3MPa.The maximum stress peak value is 92.11 MPa in torsion and 147.21 MPa in standing on one leg.While the maximum stress peak value of group b model is 229.86MPa;when walking slowly.The maximum stress peak of femoral shaft is57.07MPa.The maximum stress peak of femoral head is 10.71MPa.The maximum stress peak of the screw can reach 229.86Mpa.The highest stress peak of femoral neck can reach16.71MPa.The maximum stress peak value of the steel plate is 196.93MPa.The maximum stress peak value obtained during torsion is 86.94Mpa,and the maximum stress peak value reached by standing on one leg is 101.85Mpa.Under different loads,the maximum stress peak of the screws in the two models is the third one in the middle section,in other words,the screws installed at the fracture line.The maximum stress in group B is 38.34%lower than that in group A when walking slowly,5.94%lower when twisting and 44.53%lower when standing on one leg.The stress on femoral head and neck of group B model is also less than that of group A model.By observing the stress distribution nephogram,it can be seen that the maximum stress in the physiological state model is distributed in the medial femur,and the maximum stress is mainly concentrated in the position under the femoral neck,and the stress in the medial femur is obviously higher than that in the lateral femur.The maximum stress of the two models when standing on one leg,rotating and walking slowly is distributed on the cannulated screws,the stress distribution on the femur is similar to the physiological state,and the stress on the medial side is higher than that on the lateral side.2.Comparing and analyzing the indexes of patients in group a and group b during operation and after operation,such as the operation time or the healing time of fracture after operation,the results showed that the intraoperative blood loss of patients in group a was(60.58±14.12)ml,while that of patients in group b was(141.16±18.15)ml,and there was a significant difference between the two groups(P<0.05).Among them,the operation time of patients in group A and group B was(46.21±9.32)min and(72.47±7.89)min respectively.After a comparative analysis of the operation time between the two groups,it is found that the comparison results meet the standard of P<0.05,so the operation time between the two groups has very obvious statistical significance.The postoperative fracture healing time of patients in group A was(5.87 1.58)months,while that of patients in group B was(4.02 1.22)months.There was significant difference between the two groups(P<0.05).The postoperative walking time of patients in group A was(13.53 1.95)days,while that of patients in group B was(9.78 2.00)days.There was significant difference between the two groups(P<0.05).The total weight-bearing time of patients in group A was(5.87 1.47)months,while that of patients in group B was(4.561.13)months.There was significant difference between the two groups(P<0.05).As to the recovery of fracture in group A,the number of excellent cases in class I and class II were 12 and 11 respectively,and the excellent and good rates were 40.00%and36.37%respectively.The excellent numbers of grade III and IV were 5 and 2 cases respectively.The excellent and good rates were 160.67%and 6.67%respectively.Therefore,the total excellent and good rate reached 76.66%.In group B,18 cases were excellent(60.00%),9 cases were good(30.00%),3 cases were fair(10.00%),and 0 cases were poor(ⅳ).The excellent and good rate was 90.00%,and there was significant difference between the two groups(P<0.005).There is no statistical difference in Harris scores between the two groups before operation(P>0.05),and the Harris scores of the two groups in 3 months,6 months and 12 months after operation are significantly higher than those before operation(P>0.05),and the Harris scores are gradually increasing with the prolongation of postoperative time,which is statistically significant(P<0.05).Harris was used to compare the situation of patients in group A and B in half a year after the operation and 12 years after the operation.After comparative analysis,it was found that the postoperative situation of patients in group B was higher than that of patients in group A,and it met the standard of P<0.05.In addition,compared with 90 days after operation,the comparison data obtained by the two groups reached the standard of P<0.05,so there was no statistical significance.After the operation,the healing time of incision in group A and group B was set as stage I,and no infection or other complications occurred during the healing process of incision.Two groups of patients were interviewed immediately within one year after the operation.After the interview,it was found that the total number of femoral head necrosis occurred in Group A was 2 cases,which accounted for about6.67%compared with all patients.The total number of patients with femoral nonunion and failure of internal fixation were 2 and 2 respectively,accounting for 3.33%and3.33%respectively.Internal fixation mainly included 1 case of broken nail(3.33%),1 case of withdrawn nail(3.33%)and no femoral head cut.The total incidence of postoperative complications was 16.67%(5/30).In group B,the total number of femoral head necrosis and femoral nonunion was 1 case,and the ratio of the two cases was 3.33%and3.33%respectively.The total number of internal fixation failures is 0;After the operation,the total number of patients with complications reached about 6.67%.After statistical comparative analysis,it was found that the data of femoral head necrosis and femoral nonunion did not reach the standard of(χ~2=0.546,P=0.439),so there was no statistical significance.Compared with the failure of internal fixation,the love rat in the two groups did not reach the standard(χ~2=5.432,P=0.012),so there was no statistical significance.In addition,the study found that the control group was significantly lower than the researchers.Comparing the postoperative complications between the two groups,they did not reach the standard of(χ~2=4.315,P=0.037),so there was no statistical significance.The quality of life score of patients in group A was(71.23 5.32),and that of patients in group B was(82.15 5.28),which was statistically significant(t=6.329,P<0.05).Compared with the overall satisfaction of patients in the two groups,the total number of patients in the A/B group who expressed great satisfaction was 21 and 25 respectively.Compared with the total number of people,the proportion is 70.00%and 83.33%respectively.The total number of patients in the two groups who expressed satisfaction and dissatisfaction were 7cases and 5 cases,2 cases and 0 cases respectively.Compared with the total number of patients,the ratio reached 23.33%and 16.67%,6.67%and 0%,respectively.There was a significant difference in the total satisfaction between the two groups(P<0.05).Conclusion:(1)The stability of 3 hollow nails fixed in the shape of"品"+inner steel plate(group B)and the stability of the double set of fixing 3 hollow nails in the shape of"品"is good.(2)The biomechanical stability of the 3 hollow nails inverted"Pin"shape fixation is not significantly different from the 3 hollow nails inverted"Pin"shape fixation+inner plate fixation.(3)The 3 hollow screws inverted"pin"shape fixation+medial plate fixation space configuration fixation of femoral neck fractures all showed good mechanical stability,which is consistent with the biomechanical research results of mainstream scholars.(4)The biomechanical strength of 3 hollow nails fixed in the shape of"Pin"was the worst in this experiment.(5)This clinical study showed that the 3 hollow nails inverted"Pin"shape fixation+medial plate fixation was better than 3 hollow nails inverted"Pin"shape fixation in fracture healing time and hip joint function score.In terms of operation time,the two-screw group is significantly less than the three-screw group.Therefore,3 hollow nails inverted"Pin"shape fixation+inner steel plate fixation has better biomechanical stability than 3 hollow nails inverted"Pin"shape fixation,and double heads can be used clinically.Hollow compression screws are used to treat femoral neck fractures,especially for non-comminuted and stable femoral neck fractures,in order to achieve primary healing of the fracture.If the femoral neck is small,non-displaced or slightly displaced fractures,you can choose 3 hollow screws inverted"pin"type fixation horizontal fixation. |
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