| Objective:Through the biomechanical analysis of the modified Pauwels type Ⅲ femoral neck fracture model fixed with hollow compression screw combined with medial buttress plate,it provides a clinical strategy for the selection of reasonable internal fixation methods for the treatment of such fractures.Methods:Twenty four intact adult femur specimens were selected to simulate the vertical shear femoral neck fracture model,and osteotomy was performed according to the modified Pauwels 70°;They were randomly divided into four groups of six,with different internal fixation methods for fixation:①Group A:Using a simple three hollow compression screw for inverted triangle shaped fixed;②Group B:Using hollow compression screw combined with 1/3 tubular plate fixed,two screws in the distal osteotomy into and no screws were placed in the proximal end;③Group C:Using hollow compression screw combined with 1/3 tubular plate fixed,osteotomy in the proximal and distal screws were placed one and two;④Group D:Using hollow compression screw combined with locking compression plate fixed,insert one and two unicortical locking screws at the proximal and distal ends of the osteotomy.When all the specimens are standing on one foot in vitro to simulate the human body,the femoral shaft is fixed on the biomechanical testing machine at an angle of 15°to the vertical direction,and axial vertical compression was applied until the internal fixation failed(The sinking displacement of the femoral head is 4.7mm).Collect general information of femoral head specimens,including age(yrs old),gender,side,femoral neck shaft angle(°),femoral neck length(mm),femoral neck diameter(mm),and Ward triangle bone mineral density(g/cm2);The data of femoral head sinking displacement(mm),axial load(N),ultimate load(N)and bone strain around osteotomy fracture were recorded,and the biomechanical analysis of four groups of internal fixation methods was carried out.All the result data were processed by SPSS 26.0 statistical software.The measurement data were expressed as mean ± standard deviation(x±s).All data retain two decimal places.The t-test was used to compare the mean between the two groups.counting data were expressed as percentage(%),analyzed by χ2 test or corrected χ2 test;Variance analysis,and any two groups of multiple sample means were compared using SNK-q test;When the data does not satisfy the normal distribution and the homogeneity of variance t test,the non-parametric Mann-Whitney U rank sum test is used.P<0.05 indicates that the difference has statistical significance,P<0.01 indicates that the difference has obvious statistical significance.Results:1.Comparison of general information of four groups of femoral specimensThe four groups of femoral specimens were compared in terms of age,gender,side,femoral neck shaft angle,femoral neck length,femoral neck diameter,and Ward triangle bone mineral density,the differences were not statistically significant(P>0.05).2.Comparison of the anti-axial load capacity of the four groups of femoral specimens under different displacements of the femoral headWhen the sinking displacement of the femoral head is 1mm,2mm,3mm,and 4mm,the axial loads of the A-D group are(381.7±32.84N,593.22±28.28N,781.53±33.20N and 742.15±.16N),(664.97±.79N,996.08±28.96N,1312.58±36.27N,1261.97±47.67N),(899.03±32.52N,1361.59±97.50N,1980.00±89.11N,1923.56±.75N)and(1283.91±30.03N,1881.05±74.28N,2585.45±21.56N,2493.92±106.95N);When the femoral head sinking displacement 4.7mm,internal fixation failure occurs.At this time,the ultimate load of the A-D group are(1506.03±80.27N,2430.08± 164.54N,3102.83± 155.07N,3066.03± 114.96N);Compared with the axial load of group A,group B,group C and group D are all significantly higher,the difference is statistically significant(P<0.01);In addition,the axial load of group C and D is The different femoral head sinking displacements were significantly higher than those of group B,the difference was statistically significant(P<0.05);However,when comparing the axial load between group C and group D,the difference was not statistically significant(P>0.05).3.Comparison of the sinking displacement of the femoral head of the four groups of femoral specimens under different axial loadsUnder the axial loading load of 300N,600N,900N,and 1200N、the sinking displacement of the femoral head of the A-D group are(0.72±0.16mm,0.49+0.2±mm,0.35±0.12mm,0.38±0.19mm),(1.96±0.43mm,1.37±0.32mm,0.86±0.20mm,0.92±0.26mm),(3.05±0.25mm,2.08±0.17mm,1.42±0.27mm,1.56±0.22mm)and(3.87±0.38mm,2.87±0.25 mm,1.95±0.31mm,2.08±0.34mm);Compared with the femoral head subsidence displacement of group A,group B,group C and group D are all significantly smaller,the difference is statistically significant(P<0.01);In addition,Under different axial loading loads,the sinking displacement of the femoral head of group C and D was also significantly smaller than that of group B,the difference was statistically significant(P<0.05);However,when comparing the subsidence displacement of the femoral head between the C group and the D group,the difference was not statistically significant(P>0.05).4.Comparison of bone strain around the femoral neck osteotomy site in four groups of femoral specimens under a certain loadIn each group of femoral specimens,the upper U point and lower N point of the femoral neck osteotomy were mainly manifested as the tensile strain and compressive strain in the axial direction of the femoral neck.When a load of 1200N is loaded,the average values of the tensile strain at the upper U point and the lower N point in the A-D group at the osteotomy are(6.86±0.46%,3.72±0.23%,0.98±0.17%and 1.06±0.15%)and(2.53±0.31%,5.08±0.39%,0.79±0.16%and 0.91±0.18%).Among the four groups of femoral specimens,the tensile strain at the upper U point at the osteotomy site was significantly reduced in group B,group C,and group D compared with group A,and the difference was statistically significant(P<0.01);In addition,B The U-point tensile strain of group was higher than that of group C and group D,and the difference was statistically significant(P<0.05);but there was no statistically significant difference between group C and group D(P>0.05).In the four groups of femoral specimens,the compression strain at the lower part of the osteotomy site N point,compared with group B,group A,group C and group D were significantly reduced,the difference was statistically significant(P<0.01);In addition,group A The compressive strain at point N was higher than that of group C and group D,the difference was statistically significant(P<0.05);but there was no statistically significant difference between group C and group D(P>0.05).Conclusion:The fixing strength of the hollow screw combined with the inner support plate is significantly better than the traditional fixing method of three hollow screws;among them,the fixing method of the hollow screw combined with the 1/3 tubular steel plate or the locking compression plate(proximal nail)shows the most Excellent fixation strength;while the fixation method of hollow screw combined with 1/3 tubular steel plate(no nail at the proximal end)has good fixation strength,it can effectively transform the axial compressive stress into the fracture end compressive stress,which is beneficial to Femoral neck fracture healed.Therefore,it can be used as a clinical treatment to improve the selection of different surgical fixation methods for Pauwels type III femoral neck fractures.It provides an important biomechanical reference basis and has a good prospect of transformation and application. |
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