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Objective To study biomechanical effects of cannulated screws at different fixation angles on posterior malleolus fracture based on finite element method, so as to determine the best fixation method of cannulatedscrew. Methods The finite element model of ankle joint, including tibia, fibula, astragalus, corresponding cartilage and ligaments was reconstructed using CT images, and 1 / 2 posterior malleolus fracture model was established on the basis of verifying its validity. The biomechanical effects of cannulated screw fixation on posterior malleolus fracture fixation model were analyzed. Results Compared with 0°,5°,10°,20° fixation model, the 15° fixation model had the smallest displacement. The screw stress of 15° fixation model was lower than that of 5°, 10°, 20° fixation model, and higher than that of 0° fixation model. But when the screw fixation angle was 0°, the peak contact pressure of ankle joint was much larger than that of normal ankle joint, which was easy to cause traumatic osteoarthritis. Conclusions Cannulated screw is safe and effective for treating posterior malleolus fracture which is less than 1 / 2 fragment size. The displacement and stress of the model are different at different fixation angles of screws. When the fixation angle of screw is 15°, the biomechanical stability is the best, which can be used to guide clinical operation.
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Objective@#To compare the effects of indirect reduction, percutaneous anterior posterior screw and direct reduction, posterior anterior screw in the treatment of posterior malleolus fracture.@*Methods@#A retrospective analysis was made on 58 patients with posterior malleolus fracture treated by cannulated screw fixation from January 2013 to December 2017 in the Department of Orthopedics, Affiliated Hospital of Guangdong Medical University.They were divided into anterior and posterior screw group (26 cases) and posterior and anterior screw group (32 cases) according to different treatment methods.The incidence of poor screw position and other complications were compared between the two groups.Health status and ankle function at the last follow-up were compared between the two groups.@*Results@#The incidence of screw malposition in the anterior and posterior screw fixation group was 23.08%(6/26), which was significantly higher than that in the posterior screw fixation group was 3.85%(1/32). The difference between the two groups has statistically significant (χ2=5.381, P=0.020); there was no significant difference in other complications such as infection, traumatic arthritis, bone nonunion (all P>0.05). At the last follow-up, the OMA scores of AP group were (80.70±8.16)and PA group were(75.23±9.33), There were significant differences between the two scores(t=2.240, P=0.029), the AOFAS scores of AP group were (80.57±7.25) and PA group were(75.38±10.19), There were significant differences between the two scores(t=2.110, P=0.039).@*Conclusion@#The Indirect reduction and percutaneous anterior and posterior screw treatment have a high incidence of malposition of the screw, which has an impact on ankle function.Direct reduction and posterior and anterior screw fixation can significantly reduce the incidence of malposition of the screw and obtain better functional results.
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PURPOSE: The purpose of this study is to evaluate the usefulness of computed tomography (CT) for spiral tibia shaft fracture by analyzing associated distal tibia intra-articular fractures diagnosed by CT only which met the indication of surgical fixation and were fixed. MATERIALS AND METHODS: Ninety-five spiral tibia shaft fractures with preoperative ankle plain radiographs and CT were analyzed retrospectively. The incidence and type of associated distal tibia articular fractures were evaluated by reviewing ankle plain radiography and CT. The number of fractures diagnosed by CT that correspond with the indication of fixation and that were actually fixed were analyzed. RESULTS: Among 95 spiral tibia shaft fractures, 62 cases (65.3%) were associated with distal tibia intra-articular fracture. There were 37 cases of posterior malleolar fracture, 5 cases of avulsion fracture of the distal anterior tibiofibular ligament, 5 cases of medial malleolar fracture, and 15 cases of complex fracture. Among 52 posterior malleolar fractures including complex fracture, 20 cases were diagnosed by ankle plain radiograph. Of these 20 cases, 16 posterior malleolar fractures (80.0%) met the indication of surgical fixation, and 14 cases were actually fixed with a screw. Among 32 posterior malleolar fractures diagnosed by CT only, 26 cases (81.3%) met the indication of surgical fixation and 18 cases (56.3%) were fixed by screw. CONCLUSION: Approximately 50% of associated fractures were diagnosed by CT only and more than 80% of associated posterior malleolar fractures met the indication of surgical fixation and among these fractures, 18 cases (56.3%) were actually fixed by screw. This result suggests that CT is useful in diagnosis and treatment of distal tibia intra-articular fracture associated with spiral tibia shaft fracture.