Chen Yen-Nien, Lee Pei-Yuan, Chang Chih-Han, Chang Chih-Wei, Ho Yi-Hung, Li Chun-Ting, Peng Yao-Te
Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan; Metal Industries Research & Development Centre, Kaohsiung City, Taiwan.
Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan; Department of Orthopedics, Show-Chwan Memorial Hospital, Changhua City, Taiwan.
Injury. 2016 Oct;47(10):2339-2346. doi: 10.1016/j.injury.2016.07.001. Epub 2016 Jul 7.
Elastic stable intramedullary nailing (ESIN) is a treatment strategy for the management of diaphyseal long-bone fractures in adolescents and children, but few studies have investigated the mechanical stability of tibial diaphyseal fractures treated with various degrees of prebending of the elastic nails. Therefore, the aim of this study was to compare the mechanical stability, including the gap deformation and nail dropping, of a tibia fracture with various fracture sites and fixed with various degrees of prebending of the elastic nails by the finite element method. Furthermore, the contribution of end caps to stability was taken into consideration in the simulation.
A tibia model was developed with a transverse fracture at the proximal, middle and distal parts of the diaphysis, and fixed with three degrees of prebending of elastic nails, including those equal to, two times and three times the diameter of the intramedullary canal. The outer diameter of the nail used in the computation was 3.5mm, and the fractured tibia was fixed with two elastic double C-type nails. Furthermore, the proximal end of each nail was set to free or being tied to the surrounding bone by a constraint equation to simulate with or without using end caps.
The results indicated that using end caps can prevent the fracture gap from collapsing by stopping the ends of the nails from dropping back in all prebending conditions and fracture patterns, and increasing the prebending of the nails to a degree three times the diameter of the canal reduced the gap shortening and the dropping distance of the nail end in those without using end caps under axial compression and bending. Insufficient prebending of the nails and not using end caps caused the gap to collapse and the nail to drop back at the entry point under loading.
Using end caps or increasing the prebending of the nails to three times the diameter of the canal is suggested to stop the nail from dropping back and thus produce a more stable structure, with less gap deformation, in the management of a simulated tibial diapyhseal fracture by using titanium elastic nails with a double C-shape.
弹性稳定髓内钉固定术（ESIN）是治疗青少年和儿童骨干长骨骨折的一种治疗策略，但很少有研究探讨不同程度预弯的弹性钉治疗胫骨干骨折的力学稳定性。因此，本研究的目的是通过有限元方法比较不同骨折部位且用不同程度预弯的弹性钉固定的胫骨骨折的力学稳定性，包括间隙变形和钉体下沉情况。此外，在模拟过程中考虑了端帽对稳定性的影响。
建立一个胫骨模型，在骨干的近端、中部和远端有横行骨折，并用三种程度预弯的弹性钉固定，预弯程度分别等于、两倍和三倍髓腔直径。计算中使用的钉外径为3.5mm，骨折胫骨用两根弹性双C型钉固定。此外，每根钉的近端设置为自由状态或通过约束方程与周围骨相连，以模拟使用或不使用端帽的情况。
结果表明，在所有预弯条件和骨折类型下，使用端帽可通过防止钉端回落来防止骨折间隙塌陷，在轴向压缩和弯曲时，将钉的预弯增加到髓腔直径的三倍可减少未使用端帽情况下的间隙缩短和钉端下沉距离。钉预弯不足且未使用端帽会导致间隙在加载时塌陷，钉在入点处回落。
在使用双C形钛弹性钉模拟治疗胫骨干骨折时，建议使用端帽或将钉的预弯增加到髓腔直径的三倍，以防止钉回落，从而产生更稳定的结构，间隙变形更小。
