Biomechanical Study of Double Ring Stability Theory Guides the Treatment of Ⅳ Degree Pronation-external Rotation Ankle Fracture
Objective To verify the guiding significance of'double ring stability theory'in the treatment of Ⅳ degree pronation-external rotation ankle fracture by biomechanical methods.Methods The experimental model of ankle fracture with Ⅳ degrees of pronation-external rotation was established using 6 fresh cadaver specimens.In order to control the variables,the anterior ankle osteotomy(intact anterior inferior tibiofibular ligament),posterior ankle osteotomy(intact posterior inferior tibiofibular ligament),and resection of the interosseous tibiofibular ligament 10 cm above the ankle were done.In the complete group(working condition 1),the model group(working condition 2),the single fixed posterior ankle(working condition 3),the single fixed anterior ankle(working condition 4),and the lower tibiofibular screw fixation(working condition 5),the specimens were axially loaded 600 N,outward rotated 20°,and the parameters were obtained by CT plain scan after the ankle joint was fixed.The width of the lower tibiofibular joint space,the absolute difference of the distance between the anterior and posterior edges of the tibiofibular joint and the ratio of the lower tibiofibular joint area were measured.Results In the 6 groups of specimens,the width of the lower tibiofibular joint space in working condition 2 was significantly greater than the other working conditions(P＜0.05);the difference was not significant except working condition 2(P＞0.05).The absolute difference of the distance between the anterior and posterior edges of the tibiofibular joint of working condition 2 was greater than 2 mm,and the incidence was significantly greater than the other working conditions(P＜0.05);that of other working conditions was less than 2 mm,and the difference between the samples was not statistically significant(P＞0.05).The ratio of the lower tibiofibular joint greater than 1.56 times between working condition 2 and working condition 1 was 100％,greater than 0 in working conditions 3-5 to working condition 1,and the difference was statistically significant(P＜0.05);the incidence of working condition 3-5 to working condition 1 was not statistically significant(P＞0.05).Conclusion The'double ring stability theory'is of guiding significance for the treatment of Ⅳ degree pronation-external rotation ankle fracture.
Ankle jointLower tibiofibular jointRing theoryDouble ringHorizontal plane ring
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