Biomechanial Study And Clinical Application Of Spiral Fracture Of Low 1/3 Tibial Shaft Combined With Posterior Malleolar Fracture

Objective:To investigate the lower tibial 1/3 spiral biomechanical properties and and clinical application of Posterior Malleolar fractures combined fractures, for clinical treatment of the complex fracture and select the best operation approach and fixation methods provide theoretical basis.Methods:1. Biomechanical Study:The artificial bone (Synthetic bone) 45, simulate the normal bone structure made of middle and distal tibial 1/3 spiral experimental mechanics model of posterior malleolar fracture combined with fracture, respectively after cannulated screw fixation, L type 4 plate and the medial tibial anatomic plate combination of fixed measuring its anatomic relationship, its detection their biomechanical properties.2 Clinical application:41 cases of surgical treatment of lower tibial 1/3 fracture with posterior malleolar fracture, the tibial fracture with plate fixation, posterior malleolus by cannulated screw fixation in 23 cases (hollow nail group) and open reduction and plate fixation in 18 cases (plate group). Using the Baird-Jackson scoring system to evaluate the function of ankle joint.Result:1. Biomechanical Study: ①For lower tibial spiral 1/3 combined with posterior malleolar fracture broken end axial compressive strength and stiffness, torsional strength and stiffness with the increase of the articular surface and decrease fracture, articular surface 15%, tibia combined with posterior malleolar fracture fixation, cannulated screw fixation and triangular L type plate fixation are effective, no statistical difference (P>0.05), When the articular surface is more than 25%～50%, the ankle joint stiffness and strength even fixed will fall, the average intensity decreased 27%, stiffness decreased 36%, showed a significant difference(P<0.05); ②Posterior malleolar fracture of tibia, the change in the tibiotalar joint damage, surface contact characteristics reflect very sensitive, even when the damage surface 15%, no statistical significance, A B two fixation methods (P>0.05), when more than 25%～50%, the tibiotalar joint contact area and contact stress decreased by 29% and 13% respectively, with significant difference (P<0.05); ③Joint damage area, after the shift of posterior malleolar fracture block and the fixed effect is very obvious, the talus dislocation outward 1mm,45% reduction of tibiotalar articular contact area, or more than 15% joint injury, tibiotalar joint contact area and contact stress will increase the incidence of abnormal, traumatic arthritis.2. Clinical application:41 cases were followed up for 10-26 months with an average of 17.5 months. The hollow nail group 13 cases of excellent, good in 7 cases,2 cases,1 cases of poor, good rate of 86.9%; 9 cases of plate were excellent, good in 6 cases,2 cases,1 cases of poor, good rate of 83.3%; two groups of Baird-Jackson score excellent rate difference was not statistically significant (x2=0.11, P=0.74>0.05).Conclusion:Lower tibial 1/3 spiral fracture combined with posterior malleolar fracture, face more than 15% proposed for the operation of open reduction and rigid fixation, joint damage surface directly affects the changes of biomechanical indexes, hollow nail triangle is superior to L type plate fixation. After posterior malleolar fracture with hollow nail no obvious difference in curative effect between the hollow nail and plate internal fixation, are effective and feasible, which can reduce the surgical trauma, high healing rate, quick recovery.