Different Combinations Of Bone Plates Affect The Mechanical Environment Of Distal Femoral Fracture With Metaphyseal Comminution

Background: To identify the best biomechanical environment for distal femoral fracture with metaphyseal comminution healing by means of a biomechanical test.Methods: Distal femoral fracture with metaphyseal comminution(C2.3 AO type)was established in 40 synthetic femoral bones.The specimens were divided into five groups.The control group where they had lateral locking plating(n = 8).The remaining four groups were the experimental group.The experimental group a where they had lateral locking plating and medial locking compression plate(n = 8).The experimental group b where they had lateral locking plating and medial common compression plate(n = 8).The experimental group c where they had lateral locking plating and medial locking reconstruction plate(n = 8).The experimental group d where they had lateral locking plating and medial common reconstruction plate(n = 8).In each group 5 of the 8 specimens were used for torsion test,axial loading test and cyclic axial loading test;while the left 3 underwent axial loading threshold test.Results: In the torsion loading tests: The torsion stiffness of the control group(clockwise 2.47+0.07Nm/deg,counterclockwise 2.04+0.13Nm/deg)was significantly lower than that of group a(3.901±0.27Nm/deg,3.564±0.25Nm/deg)and group c(3.819±0.44Nm/deg,4.279±0.39Nm/deg)(p<0.05).Axial load test showed that the axial stiffness of both groups was significantly higher than that of the control group(p<0.05).The axial stiffness of group a(1850.14±89.34N/mm)and group c(1781.07±79.31N/mm)was significantly higher than that of group b(1141.27±177.86N/mm)and group d(126.25±83.27N/mm).In the axial cyclic loading experiment,two cases of nail removal occurred in inner steel plate of group b.No failure of internal fixation such as screw loosening or steel plate fracture occurred in other models.The medial compression displacement of each group was compared: The compression displacement of group a 0.15±0.06 mm,c 0.31±0.09 mm,d 0.44±0.12 mm was significantly lower than that of the control group 1.54±0.21mm(p<0.05).There was no significant difference in compression displacement between the experimental groups.The medial strain of fracture was respectively: a 0.85%,b 9.16%,c 4.04%,d 5.59%.They were all significantly lower than the control group 16.25%(p<0.05).In axial ultimate load test group a 18118±108.86 N and group b 15705±155.96 N were significantly higher than the control group 6334.33±34.39 N,group c 8697.667±162.66 N and group d 9680.667±228.22N(p<0.05).The mean values of the c and d groups were higher than that of the control group,but no statistical significance was found.Conclusion: Internal fixation with medial reconstructive plate and lateral distal locking plate for distal femoral fracture with metaphyseal comminution significantly providing a more suitable biomechanical environment for fracture healing.It can effectively promote fracture healing in theory,but it still needs clinical research to confirm.