Design And Biomechanical Analysis Of Double-locked Compressive Intramedullary Nail.

ObjectiveTo design a double-locked compressive intramedullary nail(DCIN),which not only have the compressive ability of fracture site,but also facilitate the procedures of distal locking,and compare the biomechanical properties with self-locking intramedullary nail.MethodsThe DCIN is composed with outer nail,inner nail,blade,locking screws and compressive cap.Sliding movement between outer nail and inner nail,which caused by compressive cap,is capable to compress the fracture site.Twelve-fixed tibials of adults were made into distal tibial fracture models.They were divided into 2 groups. Group 1 was fixed with DCIN and group 2 was fixed by self-locking intramedullary nail.All specimens were submitted to biomechanical test.The data were analysed by t test.ResultsIn axial compressive test,mean maximum load of group 1(2454.0±186.6) N was significantly larger(P<0.001) than that of group 2(2018.7±100.9) N.In tortsional test,mean maximum torque of group 1(6.8±1.5) N·m at 20 degrees was significantly larger(P<0.001)than that of group 2(4.6±0.8) N-m.The mean submitted point of cannulated distal locking screws in DCIN was(348.0±22.8) N.ConclusionThe results showed that anti-compressing stiffness and anti-rotating stiffness of DCIN is significantly better than that of self-locking intramedullary nail.Though the firmness of cannulated distal locking screw can meet the requirement of biological fixation,the range of weight-bearing cannot beyond 30kg to avoid failure.In general, its structure is reasonable,simple,practical,and it can resist certain harmful stress.