| Objective: Distal tibia fractures are due to the forces of axial,lateral orrotational of the distal part of the tibia. locating in the metaphysic, it is easierto happen to fracture, and the crest and the anterior medial of the tibia are lackof muscle, just only attached by the skin, when suffering the violence, it willbecame open fractures, increasing the risk of infection. Intramedullaryinterlocking nails, locking plate, external fixation can be used for thetreatment of distal tibia fractures. Open reduction and internal fixation ofdistal tibia suits for nearly all closed fracture types, whether or not involvingarticular surface of the distal tibia. Using plate fixation must follow the AOorganization’ principal: anatomic reduction, rigid internal fixation, and earlyfunctional exercise, but using it has the problem of destroys the soft tissue orblood supplely of the bone, and it decreasing the rate of fracture healing. Withthe MIPO technology promotion, distal tibia fractures can be treated by closedreduction and minimally invasive insertion plate, avoiding extensivedissection of the soft tissue, improving the rate of fracture healing.Intramedullary interlocking nails have the advantages of protecting the bloodsupply, axis fixed, so they are widely used in the long bone fractures. Theimproved intramedullary nails can also be applied to the distal tibia fracture,with certain malunion of fracture, nonunion rates, and even the need to replacethe internal fixation and bone graft. External fixation is easy to fix, so it suitfor open fracture, but there is a high rate of fracture nonunion and delayedunion rate and need reoperation. Each type of fracture treatment is not only,we should select the most suitable fixing method. Through the biomechanicsresearch, we compare the interlocking intramedullary nail, tibia distal medialanatomical locking plate and unilateral external fixation for distal tibia fracture，in order to provide a basis for choosing suitable fixing methods inclinical.Methods:6adult pairs of cadaveric lower limb specimens with anti-corrosion (provided by the Department of human anatomy of Hebei MedicalUniversity), including5males and1female, average age of36years old(21-50years), the average length of the tibia is33cm (32-35cm). Disarticulatethe tibia from the knee and ankle, retain the shaft of the tibia, and remove theskin, muscles and other soft tissue of tibia and fibular surface, retaining onlythe tibia. To except the malformations, old fracture, osteoporosis, bone tumorand other diseases of the skeletal system of the tibia, macroscopic observationand X-ray had done. A length of1cm bone defects was created with proximalto the distal tibia articular surface.12tibia specimens were randomly dividedinto A、B、C three groups. We fix group A with interlocking intramedullarynails at the center of the slope of the tibia, opening with the opening device,followed by the reaming with different diameters, and gradually expand thebone marrow cavity, finally the nail’s diameter is1mm short than the cavity.To confirm the distal intramedullary nail is located above the ankle use theX-ray. In order to maintain the accuracy of the data, we use the same diameter(9mm) intramedullary nail, and then through the aim device we make theproximal and distal locking screws of the intramedullary nail locked. Group Bwas fixed by the distal medial tibia anatomical locking plate, locating at thedistal end of the ankle mortise. The general compression screw was used tomake the plate close to the bone before the locking screws. Each side of theproximal and distal of the tibia fracture was fixed at least three locking screws.Group C used external fixation. Each side of the proximal and distal of themedial tibia we fixed2diameter5mm external fixation pins, standing a linebasically, and then connected the four fixed pins by a long rod. All groups ofspecimens were performed axial compression pressure test, rotation test, andthree point bending test respectively by the biomechanical machine.Results: In three-point bending test, with the maximum pressure, the intramedullary nail group displacement is2.0152±1.0881mm, the lockingplate group displacement of the displacement is4.0788±2.1913mm, theexternal fixation group is4.0748±2.1215mm. The locking plate group has themaximum displacement, the intramedullary nail group displacement hasminimum. The intramedullary nail group and the external fixation group has asignificantly difference (p=0.028, p<0.05), no significant difference (p=0.996)between the locking plate group and the external fixation group.In axialcompression experiments， under the maximum axial pressure， theintramedullary nail group displacement was3.0833±1.1684mm, locking plategroup displacement was5.512±0.9934mm, the external fixation group was4.472±1.4888mm, locking plate group displacement was the maximum, theintramedullary nail group displacement was the minimum. The displacementof the intramedullary nail is less than the locking plate group, they werestatistically significant difference (p=0.014, p <0.05), the intramedullary nailgroup displacement is less than the external fixation group, there were nosignificant differences between them (p=0.097), locking plate groupdisplacement is greater than the external fixation group, no significantdifference (p=0.191) between them. In the rotation test, under the maximumtorque, the intramedullary nail group torsional angle is2.735°±0.6234°, thelocking plate group torsional angle is6.4375°±1.5898°, the external fixationgroup torsional angle is2.75°±0.8974°. The locking plate group torsionalangle is the largest; the intramedullary nail group is the shortest. Theintramedullary nail group and the locking plate group has significantdifference (p=0.005, p<0.05), the intramedullary nail group and the externalfixation group has no significant difference (p=0.987), locking plate group andthe external fixation group has significant difference (p=0.005, p<0.05).Conclusion: The intramedullary nail group treatment of distal tibiafractures has an advantage in the resistance to axial compression, torsion, threepoints bending than the locking plate. Biomechanics of External fixation isbetween the intramedullary nail can be used as a good fixation for distal tibiafractures. |
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