Biomechanical Comparison And Research Of Two Internal Fixation Methods For SchatzkerⅡ Tibial Plateau Fractures

Objective: SchatzkerⅡtibial Plateau Fractures are intra-articularfractures，They occur as a result of a combination of vertical thrust andbending. the patients are older (average age is over50years) and frequentlyhave some osteoporosis. These fractures will likely continue to increase infrequency as the population ages. There are several treatment options formanaging these fractures. The following are the current surgical treatmentmethods for split-depression tibial plateau：indirect reduction and fixationincluded ligamentotaxis and percutaneous elevation of the depressedfragment，open reduction and fixation included screw，lateral L-buttress plate，golf plate，or combined, LCP and LISS internal fixation systems emerging inrecent years and so on．The current standard for treatment of split depressedtibial plateau fractures involves elevation of the depressed articular fragmentwith insertion of bone graft followed by fixation with a buttress plate and lagscrews, but there has been no “ideal” treatment method. To this end，themethod of3.5mm raft-lag screws plus golf plate，and the3.5mm lateralanatomic locking plate， are selected in this experiment to conductbiomechanical tests on the knee joint specimens of Chinese people in order todetermine the biomechanical characteristics and provide a powerful theoreticalbasis for clinical application．Method: Choose eight pairs of adult corpse lower extremity specimens，dead at the age of48-62with the average age of56．3；exclude the history ofbone diseases，trauma and metabolic diseases．All tibia specimens are dividedat knee and10cm above the ankle,and remove the soft tissues and fibula asfar as possible, only the femur and the tibia left；such pathological conditionsas fracture, tumor, deformity, severe osteoporosis are excluded via naked eye and X-ray tests. Randomly separate the specimens into A1,A2,B1,B2.DXA isused to measure bone density of the metaphysis and statistic software SPSS13.0is used to calculate whether such density variation is significant．Sign thetip of the lateral intercondylar spine tibia and outer edge of tibial plateau, thendraw a vertical line through the middle of the point，a reciprocating saw wasused to cut the split fragment via the vertical line。Using2mm K-wire to marka semicircle（D=1.5cm）on the remanent articular surface，A shaped indentorwas dropped onto the marked area until it collapse to5mm， The final modelwas representative of a split-depression Schatzker Type II tibial plateaufracture (AO/OTA Type41-B3). The depressed fragment was first reduced,followed by reduction of the split fragment,Group A is fixed with3.5mmraft-lag screws plus golf plate；Group B is fixed with3.5mm lateral anatomiclocking plate．Fix the specimen on the biomechanical test machine rigidly；Group A dopt a steel ball(D=1.5cm)to conduct a vertical loading on thecollapse area of Group A1and B1, Adopt the far end of the femur from thesame corpse to conduct a vertical loading on the tibia Plateau of group A2andB2.The displacements and loads can be recorded via computer software.Group A1and B1are recorded the loads when the collapse is2mm. Group A2and B2are recorded the displacements at the loads of400,800N，1200N andl600N and the loads when the displacement is2mm. Paired-sample T tests areused for the above data by applying SPSS13．0statistic software；if P<0．05，difference is of obvious significance.Result: When the collapse is2mm, the load of group A1is178.25±21.08N, group B1is175.25±14.73N,after Paired-sample T tests，itturns out to be that such difference is of no significance in statistics(P>O．05).Under the loads of400N，800N and1200N,the displacements of A2arerespectively0.155±0.054mm,0.295±0.014mm,0.559±0.050mm，group B2arerespectively0.154±0.061mm,0.299±0.013mm,0.570±0.056mm, afterPaired-sample T tests，it turns out to be that such difference is of nosignificance in statistics(P>O．05); Under the load of1600N, thedisplacements of group A2and B2are respectively0.955±0.099mm, 1.139±0.125mm， after Paired-sample T tests，it turns out to be that suchdifference is of significance in statistics(P<O．05), When vertical displacementof2mm is the system failure standard, the loads of group A2and B2arerespectively3164±76.315N,2853±98.297N, after Paired-sample T tests，itturns out to be that such difference is of significance in statistics(P<O．01).．Conclusion: Through biomechanical tests,it is demonstrated that3.5mmraft-lag screws plus golf plate is used to fix SchatzkerⅡtibial plateau fracturesis secure,the capacity of sustaining articular surface and axial compressionresistance is superior. Compared with the3.5mm lateral anatomic lockingplate, the biomechanical stability is better.