弹性钉结合尾帽和钢丝固定长斜形股骨干骨折的生物力学分析

Biomechanical analysis of elastic nail combined with end caps and wire fixation for long oblique femoral shaft fractures

背景:使用弹性钉治疗儿童不稳定型骨折或体质量较大的患儿,常出现短缩、成角或旋转畸形。目的:对弹性钉结合尾帽或钢丝固定股骨长斜形骨折模型进行生物力学测试,为临床合理选用内固定方式提供力学理论依据。方法:取8具小个子成人尸体股骨标本,标本从4位捐献者身上获得。建立股骨中段长斜形不稳定骨折模型,逆行插入2枚3.5 mm直径钛质弹性钉固定后,结合尾帽或钢丝捆扎,制成不同固定方式的骨折固定模型,A组为弹性髓内钉固定模型,B组为弹性髓内钉+钢丝固定模型,C组为弹性髓内钉+尾帽固定模型,D组为弹性髓内钉+钢丝+尾帽固定模型。行非破坏性的轴向压缩、四点弯曲和扭转测试,对刚度、位移和扭矩进行分析。结果与结论:①与单纯弹性髓内钉固定(A组)相比,增加尾帽固定的构型(C组)在轴向压缩测试中,刚度较A组增加509%,位移减少74%(P<0.01);②辅助钢丝固定技术(B组)在矢状面弯曲测试时刚度更大(P<0.01),位移更小(P<0.01);在冠状面弯曲测试时刚度同样更大(P<0.01),位移更小(P<0.01);扭转测试时刚度更大(P<0.01);而联合2种固定技术的D组在所有方向的测试中都可以显著改善结构刚度;③结果表明增加尾帽固定有助于增加长斜形骨折模型的轴向稳定性,辅助钢丝固定增加了扭转和弯曲载荷时结构的稳定性,上述结论可为临床治疗儿童不稳定型股骨干骨折选择内固定方法提供参考依据。

BACKGROUND:The use of elastic nails to treat children with unstable fractures or heavier children often results in shortening,angular or rotational deformities.OBJECTIVE:To provide a theoretical basis for internal fixation choice for femoral long oblique fracture by elastic nails combined with end caps or wire using biomechanical test.METHODS:An identical length oblique midshaft fracture was created in eight small adult cadaveric femurs harvested from four donors.Two 3.5-mm titanium elastic nails were introduced intramedullary into all femur models.According to the different fracture fixations,all models were divided into four groups(group A:titanium elastic nail,group B:titanium elastic nail+wire,group C:titanium elastic nail+caps,group D:titanium elastic nail+wire+caps).Nondestructive axial compression,four-point bending and torsion tests were conducted.Stiffness,displacement and torque were analyzed.RESULTS AND CONCLUSION:(1)In the axial compression tests,stiffness was increased by 509%and displacement was decreased by 74%using the titanium elastic nail+cap combination compared with titanium elastic nail alone(group A)(P<0.01).(2)The titanium elastic nail+wire combination(group B)showed larger stiffness(P<0.01)and smaller displacement(P<0.01)in the sagittal plane bending test;and as well as larger stiffness(P<0.01)and smaller displacement(P<0.01)in coronal plane bending test;and larger stiffness in torsion test(P<0.01).The end caps with wire in group D improved the stiffness significantly in all directions.(3)The results have demonstrated that end caps fixation helps to increase the axial stability of the long oblique fracture model,and combined wire fixation increases the structural stability under torsional and bending loads,which provides a good reference for clinical treatment of children with unstable femoral shaft fractures.