| Objective:In the modern time, with the development of transportation and construction, high-energy mechanism injury patients have been increasing and most of them have associated injury. High-energy injury of distal tibial facture was associated with comminuted fracture and severe soft tissue injury, which was one of the commonest injury. The treatment was difficult. In order to avoiding the side effects of cross joint fixation, we design the double unilateral external fixator with distal crossover-nail fixation for the injury. This thesis was mainly to compare the fixed strength among the double unilateral external fixator, circular external fixator and hybrid external fixator by the ways of the biomechanical test. And 29 patients with high-energy injuries of distal tibia were followed up for evaluating clinical curative effect of the double unilateral external fixator. The double unilateral external fixator may provide a better method for the patients with distal tibia high-energy injuries.Methods:1 The biomechanical comparison between double unilateral external fixator with cross pins fixation and the others two different fixators:nine fresh frozen specimens of human tibias were selected, and made into distal tibial fracture models of 4.3.A3 according to the AO/ASIF classification. The models were stabilized with circular external fixator, double unilateral static external fixator and hybrid external fixator respectively. Then each model was loaded at standard vertical and torsional loading on the biomechanical test machine. The data was recorded and analyzed using statistical software SPSS 13.0.2 The clinical application:Since January 2009 to December 2010, there were 32 patients with distal tibia high-energy injuries treated with double unilateral external fixation, but only 29 patients had intact clinical follow-up data. Of which,23cases were open fracture. According to Gustilo-Anderson type, all of them were more than typeⅡ. six cases were closed fracture, of which four cases was the stage II based on Tsherne classification. According to AO/ASIF classification, seven cases were type A2, twenty cases were type A3 and two cases type C2. All of the 29 patients had seriously soft tissue injury of the distal tibial, and three cases had severe laceration of the anterior tibial muscle, one cases was associated with ipsilateral acetabular fracture, eight cases were associated with ipsilateral femoral fractures, two cases were associated with contralatcral foot injury, and one cases was associated with pelvic fracture and urethral rupture. The fracture healing time, complications and ankle activities range were recorded during the follow-up time.Results:1 The results of biomechanical test:In the axial compression test, the displacement of fracture gradually increased as the load strength increases. When load strength was 500N, the displacement of circular external fixator group, double unilateral static external fixator group and hybrid external fixator group were 4.106±0.014mm,1.158±0.001mm, and 6.027±0.137mm respectively. In the torsional test, as the torque increases, the torsion angle was increasing. When the torque turning to 10Nm, the torsion angle of circular external fixator, double unilateral static external fixator and hybrid external fixator were 31.608±0.566°,25.815±1.068°, and 43.928±0.572°respectively.According to the results, in the vertical loading test, the displacement of the double unilateral external fixator group was less than those of circular external fixator group and hybrid external fixator group, there was significant statistical difference (P<0.01). In torsional test, the torsion angle of circular external fixator group and hybrid external fixator group was less than that of the double unilateral static external fixator group, there was significant statistical difference (P<0.01).2 The results of clinical follow-up:2.1 Results of fracture union The 29 patients received 5-22months follow-up, with an average of 13 months. All of them achieved fracture union with good joint function, but five cases were delayed union. All of them had open fracture with serious bone defects, and got bone union after secdonary autologous iliac bone graft operation. 2.2 Ankle joint functionsThe patient was advised to have functional exercise of ankle and toe in the first day after operation, to have walking with crutches three days later, have weight-bearing walking about three months later. 2.3 Infection and other complicationsNine patients had pin tract response(accounted for 31%),and got better through intensive care pin tract care,using antibiotic simultaneously. Five cases whose injury were serious GustiloⅡandⅢrespectively got wound infection. Four cases got better through skin-grafting and adjustment of antibiotics, one case got exposed bone because of the necrosis of soft tissue, and got healing through the flap.Conclusion: 1 The biomechanical test data indicated that the displacement of the double unilateral external fixators group was less than those of circular external fixator group and hybrid external fixator group, the torsion angle of circular external fixator group and hybrid external fixator group was less than that of the double unilateral static external fixator group. It means that:the double unilateral external fixator with cross pins configuration had adequate anti-compression stiffness stability and excellent anti-torsion biomechanical properties. This provides theory basis for clinical application.2 Through the follow-up of the cases, it could be concluded that the application of this method had advantages such as minimally invasive, stable fixation, good reduction, early functional exercise, low incidence of nonunion, rare complication and so on. It could be recommended as a option for terminal treatment.
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