The Design Of Experiment Model With Biomechanical Comparative Study To Internal Fixation And The Improvement Of Operative Approach In Pilon Fracture

Objective: To design experimental model of "AO" C2 type distal tibial fracture for biomechanical measurement of internal fixation in pilon fracture. Compare the biomechanical character of four kinds of internal fixation plate, so as to provide the mechanical basis for clinical application. Transform the open reduction and internal fixation into minimally invasive percutaneous osteosynthesis with the improvement of traditional approach.Methods:1. To get 5 left leg specimens from flesh-frozen health adult cadaver, make a 5mm deossification at the place of 3cm above ankle joint to simulate thrypsis of tibial metaphysis; split the distal bone block fore and aft to the distal articular surface of tibia, to simulate simple fracture. Manufacture the experimental model of"AO"C2 type distal tibial fracture. After fixed by four kinds of plate, the stress and displacement of the bone block were measured when the foot was at the same axial pressure and inthe position of neutrality,enstrophe,ecstrophy,plantar flexion and dorsiflexion, respectively. Analyze the stress and displacement with SPSS 12.0.2. Improve traditional approach of pilon fracture.Results:1. The biomechanical test:(1)The displacement of interior bone block: Median comparison:Which of the groups of clover plate and improved clover plate are minimum, the group of interior anatomy plate was the next, the group of lateral anatomy plate is maximum. Wilcoxon ranking test result:There are no significant difference between the group of clover plate and the group of improved clover plate under all of the conditions. (p＞0.05).The displacement in the group of interior anatomy plate has significant difference comparing with the group of clover plate when the ankle joint is on enstrophe 20°,30°,plantar flexion 15°,dorsiflexion 8°,16°(p＜0.05), and has no significant difference under the rest conditions. The displacement in the group of lateral anatomy plate has significant difference comparing with the group of dover plate under all of the conditions (p＜0.05).(2)The displacement of lateral bone block: Median comparison:Which of the groups of clover plate,improved clover plate and interior anatomyZ.(3)Displacement comparison between the interior bone block and the lateral bone block: The lateral bone block is greater than the interior bone block, there are significant difference between them(p＜0.001).2 Improvement of approach:The expose of the ankle joint is clear and the insertion of the plate issimple and easy with the application of the arcuated incision before or behind medial malleolus.Conclusions:1. It is the first time of the design of the experimental pilon fracture model, which is consistent with the clinical actuality and suitable for the biomechanical test.2. The lateral block of pilon fracture has a risk of collapse after fixed by the plate, so additional screw and bone graft is necessary.3. The lateral anatomy plate has no mechanical superiority when the main fracture line lies in vertical plane in distal fracture of tibia.4. The expose of the ankle joint is clear and the insertion of the plate is simple and easy with the application of the arcuated incision before or behind medial malleolus.