Abstract：
OBJECTIVE: There are concerns regarding nail/medullary canal mismatch and initial stability after cephalomedullary nailing in unstable pertrochanteric fractures. This study aimed to investigate the effect of an additional anteroposterior blocking screw on fixation stability in unstable pertrochanteric fracture models with a nail/medullary canal mismatch after short cephalomedullary nail (CMN) fixation.
METHODS: Eight finite element models (FEMs), comprising four different femoral diameters, with and without blocking screws, were constructed, and unstable intertrochanteric fractures fixed with short CMNs were reproduced in all FEMs. Micromotions of distal shaft fragment related to proximal fragment, and stress concentrations at the nail construct were measured.
RESULTS: Micromotions in FEMs without a blocking screw significantly increased as nail/medullary canal mismatch increased, but were similar between FEMs with a blocking screw regardless of mismatch. Stress concentration at the nail construct was observed at the junction of the nail body and lag screw in all FEMs, and increased as nail/medullary canal mismatch increased, regardless of blocking screws. Mean stresses over regions of interest in FEMs with a blocking screw were much lower than regions of interest in those without. Mean stresses in FEMs with a blocking screw were lower than the yield strength, yet mean stresses in FEMs without blocking screws having 8 mm and 10 mm mismatch exceeded the yield strength. All mean stresses at distal locking screws were less than the yield strength.
CONCLUSIONS: Using an additional anteroposterior blocking screw may be a simple and effective method to enhance fixation stability in unstable pertrochanteric fractures with a large nail/medullary canal mismatch due to osteoporosis.
METHODS: Eight finite element models (FEMs), comprising four different femoral diameters, with and without blocking screws, were constructed, and unstable intertrochanteric fractures fixed with short CMNs were reproduced in all FEMs. Micromotions of distal shaft fragment related to proximal fragment, and stress concentrations at the nail construct were measured.
RESULTS: Micromotions in FEMs without a blocking screw significantly increased as nail/medullary canal mismatch increased, but were similar between FEMs with a blocking screw regardless of mismatch. Stress concentration at the nail construct was observed at the junction of the nail body and lag screw in all FEMs, and increased as nail/medullary canal mismatch increased, regardless of blocking screws. Mean stresses over regions of interest in FEMs with a blocking screw were much lower than regions of interest in those without. Mean stresses in FEMs with a blocking screw were lower than the yield strength, yet mean stresses in FEMs without blocking screws having 8 mm and 10 mm mismatch exceeded the yield strength. All mean stresses at distal locking screws were less than the yield strength.
CONCLUSIONS: Using an additional anteroposterior blocking screw may be a simple and effective method to enhance fixation stability in unstable pertrochanteric fractures with a large nail/medullary canal mismatch due to osteoporosis.
摘要：
目的：对于不稳定型股骨粗隆间骨折，头端髓内钉钉/髓管不匹配和初始稳定性存在顾虑。这项研究旨在研究在短的头髓内钉（CMN）固定后钉/髓管不匹配的不稳定股骨转子骨折模型中，额外的前后位阻塞螺钉对固定稳定性的影响。
方法：八个有限元模型（FEM），包括四个不同的股骨直径，有和没有阻塞螺钉，被建造，和不稳定型股骨粗隆间骨折固定短CMNs在所有FEM中再现。并测量指甲结构处的应力集中。
结果：随着钉/髓管不匹配的增加，没有阻塞螺钉的FEM的微运动显着增加，但无论不匹配，带有阻塞螺钉的FEM之间都相似。在所有FEM中，在钉体和方头螺钉的交界处观察到钉结构处的应力集中。并随着指甲/髓管不匹配的增加而增加，无论阻塞螺钉。具有阻塞螺钉的FEM中感兴趣区域的平均应力远低于没有阻塞螺钉的感兴趣区域。使用阻塞螺钉的FEM的平均应力低于屈服强度，然而，在没有8mm和10mm不匹配的阻塞螺钉的情况下，FEM的平均应力超过了屈服强度。远端锁定螺钉处的所有平均应力均小于屈服强度。
结论：对于不稳定型股骨转子骨折，由于骨质疏松导致较大的钉/髓管不匹配，使用额外的前后位封闭螺钉可能是一种简单有效的方法，可以增强固定稳定性。
方法：八个有限元模型（FEM），包括四个不同的股骨直径，有和没有阻塞螺钉，被建造，和不稳定型股骨粗隆间骨折固定短CMNs在所有FEM中再现。并测量指甲结构处的应力集中。
结果：随着钉/髓管不匹配的增加，没有阻塞螺钉的FEM的微运动显着增加，但无论不匹配，带有阻塞螺钉的FEM之间都相似。在所有FEM中，在钉体和方头螺钉的交界处观察到钉结构处的应力集中。并随着指甲/髓管不匹配的增加而增加，无论阻塞螺钉。具有阻塞螺钉的FEM中感兴趣区域的平均应力远低于没有阻塞螺钉的感兴趣区域。使用阻塞螺钉的FEM的平均应力低于屈服强度，然而，在没有8mm和10mm不匹配的阻塞螺钉的情况下，FEM的平均应力超过了屈服强度。远端锁定螺钉处的所有平均应力均小于屈服强度。
结论：对于不稳定型股骨转子骨折，由于骨质疏松导致较大的钉/髓管不匹配，使用额外的前后位封闭螺钉可能是一种简单有效的方法，可以增强固定稳定性。
