新型阻挡钉联合髓内钉治疗胫骨远端骨折的生物力学分析

Treatment of distal tibial fractures with novel blocking screws plus intramedullary nails:a biomechanical analysis

目的分析新型阻挡钉治疗胫骨远端骨折的生物力学特性。方法人工胫骨(30根)制备胫骨远端不稳定骨折模型(AO 43-A3型),根据固定方法不同分为3组(n=10):无阻挡钉组(髓内钉,阻挡钉处仅留预植孔)、传统阻挡钉组(髓内钉联合前-后向传统阻挡钉)和新型阻挡钉组(髓内钉联合侧方新型阻挡)。3组模型分别完成侧方弯曲应力试验(记录髓内钉的横向最大位移)、疲劳试验(观察模型结构异常情况)和轴向应力试验(记录髓内钉-骨结构的轴向最大位移)。观察3组模型有无结构异常,并比较3组模型髓内钉的横向最大位移和髓内钉-骨结构的轴向最大位移。结果侧方弯曲应力试验中无阻挡钉组、传统阻挡钉组、新型阻挡钉组的髓内钉横向最大位移分别为(5.02±1.03)、(4.19±0.64)、(4.18±0.65)mm。与无阻挡钉组相比,传统阻挡钉组的横向最大位移减少了16.6%(P=0.027),新型阻挡钉组的位移减少了16.8%(P=0.025),差异均有统计学意义;而传统阻挡钉组、新型阻挡钉组的横向最大位移比较差异无统计学意义(P=0.978)。疲劳试验中所有模型在循环加载中均未出现结构异常。轴向应力试验中无阻挡钉组、传统阻挡钉组、新型阻挡钉组的髓内钉-骨结构最大位移分别为(5.69±0.75)、(5.31±0.61)、(5.51±0.65)mm,3组间比较差异均无统计学意义(P>0.05)。结论新型阻挡钉增加的髓内钉-骨结构的稳定性与传统阻挡钉相当,且其他生物力学特性相似,新型阻挡钉为阻挡钉的临床应用提供了新的思路和方法。

Objective To characterize the biomechanical performance of our self-designed novel blocking screws in the treatment of distal tibial fractures.Methods Thirty artificial composite tibial bones were used to create models of unstable distal tibial fracture(AO type 43-A3)which were randomized into 3 even groups(n=10)according to modes of fixation.Group A was subjected to fixation with intramedullary nails only with merely preset holes reserved for the blocking screws,group B to fixation with intramedullary nails plus conventional anteroposterior blocking screws,and group C to fixation with intramedullary nails plus novel lateral blocking screws.In all the 3 groups,a lateral bending stress test was conducted to record the maximum transversal displacement of the intramedullary nail,a fatigue test to observe the structural abnormality in the model and an axial stress test to record the maximum axial displacement of the intramedullary nail-bone structure.The 3 groups were compared in structural abnormality,the maximum transversal displacement of the intramedullary nail and the maximum axial displacement of the intramedullary nail-bone structure.Results The lateral bending stress tests showed the maximum transversal displacements were(5.02±1.03)mm;(4.19±0.64)mm and(4.18±0.65)mm in groups A,B and C;compared with group A,the maximum transversal displacement decreased by 16.6%(P=0.027)in group B and decreased by 16.8%(P=0.025)in group C,showing significant differences but there was no significant difference in the maximum transversal displacement between groups B and C(P=0.978).In the fatigue test,all models showed no structural abnormality under cyclic loading.In the axial stress test,the maximum axial displacements of the intramedullary nail-bone structure were,respectively,(5.69±0.75)mm,(5.31±0.61)mm and(5.51±0.65)mm in groups A,B and C,showing no statistically significant difference among the 3 groups(P>0.05).Conclusion Our self-designed novel blocking screws can be a new means in clinical application,because they are similar to conventional blocking screws in increasing the stability of nail-bone construct and other biomechanical performance.