| Objective To mesure anatomical parameters of the sacral cortical bone trajectory,and the three-dimensional finite element was used to evaluate the differences of pull-out strength and stability of screw between the cortical bone trajectory(CBT)screw and the traditional trajectory(TT)screw.Method Select patient imaging data from pelvic spiral CT scan at the First Affiliated Hospital of Nanhua University from January to August 2017.Excluding Sacral fractures or anatomical abnormalities,pelvic CT scan data were obtained from 30 patients with normal anatomy of the sacrum.Aged 35-70 years old,with an average age of 52.6 years,including 15 males and females.Three-dimensional model of tibia was established using three-dimensional reconstruction software(Mimics,geomagic),and a screw model was established on solidworks,The cortical bone trajectory placement method was used to simulate the placement of nails and correlative measurements of cortical bone screw path parameters were performed.The measurement parameters including the cephalad angle to the sacral endplate line(A).the length of trajectory(B).The maximum anteroposterior length for sacral endplate penetration(C)and the anteroposterior diameter of the sacral body(D).Retrospectively selected CT imaging data of 5 female osteoporosis patients.Excluding Sacral fractures and anatomical abnormalities.All of these patients were female with T value of bone mineral density less than-2.5 SD.Age 53-65 years old,average age 55.6 years old,A three-dimensional finite element model of the sacrum in one patient was established.And simulated the traditional pedicle screw fixation and cortical bone trajectory fixation.The traditional trajectory screw size is 6.5*45mm,Cortical bone trajectory screw size is 6.5*35mm,Five sets of different elastic moduli were obtained based on the CT values of five patients and then assigned according to the elastic modulus.Analyze and compare the maximum pullout strength and stability of two kinds of trajectory screws.Result 1.Morphometric measurement of the Cortical bone Trajectory: The results of the male measurement parameters showed: the left cephalad angle to the sacral endplate line :(28.61±2.23),the right cephalad angle to the sacral endplate line :(29.14±2.20);the cephalad angle to the sacral endplate line of the left and right sides has no statistical significance(P > 0.05).the left length of trajectory :(31.21±1.47),and the right length of trajectory :(31.19±1.50);The length of trajectory of the left and right sides has no statistical significance(P>0.05).the left maximum anteroposterior length for sacral endplate penetration :(27.34±1.70),and the right maximum anteroposterior length for sacral endplate penetration:(27.14±1.69).The maximum anteroposterior length for sacral endplate penetration of the left and right sides has no statistical significance(P>0.05).The results of female measurement parameters showed: the left cephalad angle to the sacral endplate line :(27.89±1.82),the right cephalad angle to the sacral endplate line :(28.52±2.54);the cephalad angle to the sacral endplate line of the left and right sides has no statistical significance(P > 0.05).the left length of trajectory :(30.57±2.14),and the right length of trajectory :(30.92±2.26);The length of trajectory of the left and right sides has no statistical significance(P>0.05).the left maximum anteroposterior length for sacral endplate penetration :(27.27±1.62),and the right maximum anteroposterior length for sacral endplate penetration:(27.96±1.56).The maximum anteroposterior length for sacral endplate penetration of the left and right sides has no statistical significance(P>0.05).The results of measurement parameters between men and women showed: the cephalad angle to the sacral endplate line:27.88±1.82(man group),28.52±2.54(women group);the length of trajectory:30.56 ±2.13(man group),30.92±2.26(women group);the maximum anteroposterior length for sacral endplate penetration:27.27±1.62(man group),27.95±1.56(women group);the anteroposterior diameter of the sacral body:34.72±1.33(man group),33.1±1.42(women group);There was no statistical difference between men and women(P<0.05).In summary,the mean cephalad angle to the sacral endplate line was(28.54±2.20)°,the mean length of trajectory was(30.97±1.84),The mean maximum anteroposterior length for sacral endplate penetration was(27.42±1.63)mm,the mean anteroposterior diameter of the sacral body was(33.85±1.33)mm.2.Maximum pullout strength and screw stability for two different trajectory: Comparison of the maximum pullout strength: the maximum pullout strength of the CBT screw and the maximum pullout strength of the TT screw were(886.00±26.08)N and(688.00±10.95)N,respectively,and the difference was statistically significant(p<0.001).Comparison of screw stability : The ratio of load displacement of the TT screw in the upper direction was(770.80±6.42)N/mm,and that of the CBT screw was(940.00±18.70)N/mm,the difference was statistically significant(t=19.141,p<0.001);the TT screw was loaded in the downward direction The displacement ratio was(701.00±10.32)N/mm,and the CBT screw was(916.20±14.26)N/mm,the difference was statistically significant(t=27.344,P<0.001);the ratio of load displacement of the TT screw in the left direction was(836.40).±6.88)N/mm,CBT screws were(1063.60±35.58)N/mm,the difference was statistically significant(t=14.020,P<0.001);the ratio of the TT screw displacement in the right direction was(790.40±9.24)N/ Mm,CBT screws(1045.40±42.76)N/mm,the difference was statistically significant(t=13.041,P<0,001)Conclusion 1.The three-dimensional reconstruction software measurement is a reliable and easy method.The ideal tibial cortical bone screw and tibial upper endplate have a head inclination of(28.54±2.20)°,and the length of the nail path is(30.97±1.84)mm.The maximum puncture distance of the plate was(27.42±1.63)mm,and the anteroposterior diameter of the humerus was(33.85±1.33)mm.The three-dimensional reconstruction software was used to conduct the anatomic measurement of cortical bone screw patella,which could provide a certain reference value for clinical application.2.Successfully established a three-dimensional finite element model of osteoporotic sacrum.In patients with osteoporosis,The and screw stability of cortical bone trajectory screw are stronger than those of traditional pedicle trajectory screw,it can be used as an alternative to traditional pedicle screw fixation... |
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