Objective The aim of this study was to compare the interfragmentary compressive force and area of compression generated by cortical screws inserted as either a lag screw or position screw in simulated lateral humeral condylar fractures.

Study Design Ex vivo biomechanical study.

Materials and Methods Thirteen pairs of cadaveric humeri from skeletally mature Merinos with simulated lateral humeral condylar fractures were used. Pressure sensitive film was inserted into the interfragmentary interface prior to fracture reduction with fragment forceps. A cortical screw was inserted as a lag screw or a position screw and tightened to 1.8Nm. Interfragmentary compression and area of compression were quantified and compared between the two treatments groups at three time points.

Results After fracture reduction using fragment forceps (Time point 1: T1), there was no significant difference in interfragmentary compression and area of compression between the two treatments. A combination of fragment forceps and a cortical screw inserted as a lag screw (Time point 2: T2) produced significantly greater interfragmentary compression and area of compression compared with the same screw inserted as a positional screw. After removal of the fragment forceps, leaving only the cortical screw (Time point 3: T3), both the interfragmentary compression and area of compression remain significantly greater in the lag screw group.

Conclusion Lag screws generate a greater force of compression and area of compression compared with position screws in this mature ovine humeral condylar fracture model.

目的 本研究的目的是比较在模拟肱骨外侧髁骨折中作为拉力螺钉或定位螺钉插入的皮质螺钉所产生的骨折块间压缩力和压缩面积。

研究设计 离体生物力学研究。

材料和方法 使用来自骨骼成熟的美利奴人的十三对尸体肱骨，模拟肱骨外侧髁骨折。在用碎片钳复位骨折之前，将压敏膜插入碎片间界面。将皮质螺钉作为拉力螺钉或定位螺钉插入，并拧紧至 1.8Nm。在三个时间点对两个治疗组之间的骨折块间压缩和压缩面积进行量化和比较。

结果 使用骨折钳进行骨折复位后（时间点1：T1），两种治疗之间的骨折块间压缩和压缩面积没有显着差异。与作为定位螺钉插入的相同螺钉相比，碎片钳和作为拉力螺钉插入的皮质螺钉的组合（时间点2：T2）产生显着更大的碎片间压缩和压缩面积。去除碎片钳后，仅留下皮质螺钉（时间点3：T3），拉力螺钉组的碎片间压缩和压缩面积仍然显着更大。

结论 在成熟的绵羊肱骨髁骨折模型中，与定位螺钉相比，拉力螺钉产生更大的压缩力和压缩面积。