| objective:Fracture of tibial plateau is a kind of complicated internal joint fracture, normally originated from high-energy injuries. For such complicated tibial plateau fracture, including SchatzkerⅤandⅥtypes, it exists on the plateaus at both sides making treatment more difficult and it is always not easy to find out a balance point between satisfactory reduction/fixation and avoidance of further injury to soft tissues. In the principle of AO rigid internal fixation, the traditional surgical method is to adopt supporting steel plates at inner and outer sides while open reduction is conducted so as to obtain secure stability. However the inner side of the tibia lacks of muscle coverings and use of supporting steel plates needs extensive coming-off of soft tissues; therefore, after surgery, the cut is subject to infection or doesn't heal because of too large skin tension, even results in osteomyelitis. The treatment method of steel-plate fixation at one side reduces the complication diseases of soft tissues, but doesn't provide stable fixation for serious comminuted tibial plateau fractures. The following are the current surgical treatment methods for tibial plateau amphicondylous fractures,i.e.,percutaneous or limited open reduction plus external fixation supports; rigid supporting steel-plates to be used at the outer side and short-segment anti-skid steel plates at the inner side;LCP and LISS internal fixation systems coming from MIPPO technology and emerging in recent years and so on. However, how to reasonably select these methods is still in dispute. To this end, the method of supporting steel-plates at the outer side and short-segment anti-skid/reconstruction plates at the inner/rear side, and the traditional method of supporting steel-plates at both sides, are selected in this experiment to conduct biomechanical tests on the knuckle joint specimens of Chinese people in order to know their biomechanical properties and provide a powerful theoretical basis for clinical application. Method: Choose six pairs of adult corpse tibia specimens, male, dead at the age of 54-68 with the average age of 60.1; exclude the history of trauma, bone diseases and metabolic diseases. All tibia specimens are divided at knuckles and ankles and soft tissues removed as far as possible; such pathological conditions as malformation and serious osteoporosis are excluded via X-ray tests. QCT is used to measure bone density at the metaphysis and calculate whether such density variation is significant in statistics.Randomly separate the specimens into two groups and use an electric rack saw to cut the tibial plateau from its center to its inner and outer sides at 20°and 35°respectively; then connect the cutting points at both sides for further cutting so as to form a triangular fracture model, i.e., a Schatzker Vl tibial plateau fracture model. Upon fracture reduction, Group A is fixed with supporting steel-plates at the outer side and short-segment anti-skid/reconstruction steel-plates at the inner/rear side; Group B is fixed with supporting steel plates at both inner and outer sides. After molding, both groups are subject to X-ray tests to verify whether fracture reduction is successful and the implantation position of inner fixation is correct. Put the specimen into the biomechanical test machine and fix it; then adopt the far end of the thighbone from the same corpse to conduct a vertical loading experiment in mechanics. The loads of the specimens and their displacements can be achieved via specific computer software. As comparative data, take specimen displacement values at the loads of 800N, 1000N and1200N and the loads when the displacement is 3cm; t-tests of paired design are carried out for the above data by applying SPSS12.0 statistic software; in case of P<0.05, difference is of obvious significance and a conclusion will be obtained. Result:For the group of supporting steel-plates at the outer side plus short-segment anti-skid/reconstruction plates at the inner/rear side, the longitudinal compression displacements under the loads of 800N, 1000N and 1200N are respectively 0.285±0.046mm, 0.379±0.039mm and 0.486±0.040mm. For the group of supporting steel-plates at both inner and outer sides, the displacements are respectively 0.271±0.041mm, 0.361±0.042mm and 0.464±0.04mm. After paired t-tests, it turns out to be that such variation is of no significance in statistics(P>0.05). The vertical displacement of 3cm is the system failure criteria; at this time, the load is 2768±32.484N for the group of supporting steel-plates at the outer side plus short-segment anti-skid/reconstruction plates at the inner/rear side; and the load is 2804±39.090N for the group of supporting steel-plates at both inner and outer sides. After paired t-tests, it is also proved that such variation is of no significance in statistics(P>0.05). Conclusion:It is demonstrated through biomechanical tests that, when the method of supporting steel-plates at the outer side plus short-segment anti-skid/reconstruction plates at the inner/rear side is used to fix SchatzkerⅥtibial plateau fractures, such fixation is secure and the capacity of axial compression resistance is excellent; there is no significant difference in stability compared with the traditional method of supporting steel-plates at both inner and outer sides. Hence it can be deemed that using small-sized anti-skid steel plates at the inner/rear side, in place of traditional large-sized supporting steel-plates will not obviously reduce fixation stability. |
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