Biomechanical Evaluation Of The Laboratory Comparison Of Intramedullary Nails With Locked Plates On The Fixation Of Distal Tibial Fractures

Objective:Fracture of the distal tibial metaphysis typically occure as a result of axial and rotational forces on the lower extremity and represent a majority of fractures of the distal end of the tibia.The management of these distal injuries is often more complex than the treatment of tibia diaphyseal fractures,leading to the potential for postoperative complications and poor outcome.Although different treatment methods have been developed for distal tibia fractures,there is currently no consensus on the optimal mode of management.Traditional management of distal tibia metaphyseal fractures with open reduction and plate fixation often requires an extensive surgical approach, which can lead to devitalization of the surrounding soft tissue,wound complications,infection,and postoperative ankle stiffness.Fracture fixation with intramedullary nails was developed in an effort to limit these potential operative complications.The use of intramedullary nails obviates the need for extensive surgical dissection,spares the extraosseous blood supply,and allows the device to function in a load-sharing manner.However, intramedullary management of distal tibia metaphyseal fractures is accompanied by its own complications, including malalignment,hardware failure,and the risk of fracture propagation into the ankle joint.Locked plate designs act as fixed-angle devices whose stability is provided by the axial and angular stability at the screw-plate interface instead of relying on the frictional force between the plate and bone,which is thought to preserve the periosteal blood supply around the fracture site. Locked plates are indicated for fracture management in osteoporotic bone and in periarticular fracture patterns, making them a feasible treatment option for distal tibia metaphyseal fractures.This study was performed to compare the mechanical properties and fixation stability of intramedullary nails versus locked plates used in the management of distal metaphyseal tibia fractures in a cadaveric model.Methods:8 pairs of cadaveric tibia-fibula specimens were separated into two groups,each of the group was included 4 pairs specimens.The first was the fibular intact group,the second was fibular osteotomy group.A simulated,distal metaphyseal tibia fracture was created in the first group of cadaveric tibia-fibula specimens.A 0.5cm fracture gap was created with 7cm proximal to the distal tibia articular surface.The left of each pair was treated using an intramedullary nail and the right with a locked plate.After the fixation,each of the cadaveric tibia-fibula specimens was riveted by self-made clamp.The clamp was needed pegged the specimen in the distal and proximal points.Each specimen was first placed on the biomechanical test machine for torisional test.The fixed specimen turn to 250 Nmm in 10 Nmm/s by extorsion rotation.Then we could write down the torisional degree. Next step the specimen was test in axial compression.Axial compressive loading at central was loaded at a rate of 10N/second to a maximum load of 750N for each test. Displacement were determined by the position of the loading actuator during testing.Then we should create a 0.5cm gap on the fibular in the middle part with an oscillating saw to the second group.A 0.5cm fracture gap was created in the fibula by removing bone.The left of each pair was treated using an intramedullary nail and the right with a locked plate.The method was like the fibular intact group with the torisional test and the axial compressive loading test.Then we could get the torisional degree and axial displacement.Results:When the fibular intact,the degree of locked plate group was 2.9650±0.25436°under torisional loading turn around to 250Nmm,the intramedullary nail group was 3.9500±0.16021°,they were statistically significant difference(P＜0.05).Displacement of locked plate group was 1.7175±0.86812mm under axial compressive loading to 750N,the intramedullary nail group was 2.2225±0.75425mm,they were no statistically significant difference(P＞0.05).After fibular osteotomy, the degree of locked plate group was 4.0800±0.94209°under torisional loading turn around to 250Nmm,the intramedullary nail group was 11.0975±1.0822°,they were statistically significant difference(P＜0.05). Displacement of locked plate group was 2.2450±1.4638mm under axial compressive loading to 750N,the intramedullary nail group was 2.4250±1.24981mm,they were no statistically significant difference(P＞0.05).When fixation with locked plated, the fibular intact group was 27.33%stiffer than the fibular osteotomy group in torisional,28.88%in axial. When fixation with intramedullary nail the fibular intact group was 64.41%stiffer than the fibular osteotomy group in torisional,8.35%in axial.Conclusion:This study demonstrated that,in the treatment of distal metaphyseal tibia fractures,locked plates provided more stable fixation than intramedullary nails in torsional loading.An intact fibula in the presence of a distal tibia fracture improved the fracture fixation stability for both treatment methods.In fracture patterns in which the fibula cannot be effectively stabilized,locked plates offer improved mechanical stability when compared with locked intramedullary nails.