Luria Shai, Hoch Sarah, Liebergall Meir, Mosheiff Ram, Peleg Eran
Department of Orthopedic Surgery, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
J Hand Surg Am. 2010 Aug;35(8):1246-50. doi: 10.1016/j.jhsa.2010.05.011.
PURPOSE: The hypothesis of this study was that more stable fixation of acute scaphoid fractures may be achieved by a screw placed perpendicular to the fracture plane than along the long axis of the scaphoid, as previously suggested. We examined this assumption on different fracture patterns using a finite element analysis model. METHODS: A computed tomography scan of an intact scaphoid of a young man provided the data set for all fracture models. We used semiautomatic segmentation to create 3-dimensional computer models of the 3 simple fracture configurations: oblique, transverse waist, and proximal fractures, according to the Herbert classification. Each fracture type was analyzed, using finite elements, for its biomechanical response to 2 types of virtual fixation: a screw placed either perpendicular to the fracture plane or centrally along the long axis of the scaphoid. We measured motion at the fracture plane (in millimeters) and strain in the screw threads (in millipascals). RESULTS: Considerably less motion was measured at the fracture plane with the perpendicular screw compared with the long axis screw, especially in the oblique-type fractures: (1) Herbert-type B1 oblique fracture mean motion of 0.05 mm (+/-0.03) for the perpendicular screw versus 0.28 mm (+/-0.05) for the long axis screw; (2) B2 transverse waist fracture mean motion of 0.06 mm (+/-0.03) for the perpendicular screw versus 0.18 mm (+/-0.06) for the long axis screw; and (3) B3 proximal fracture mean motion of 0.07 mm (+/-0.01) for the perpendicular screw versus 0.28 mm (+/-0.011) for the long axis screw. Higher strains were measured on the screw placed perpendicular to the fracture. CONCLUSIONS: According to this model, higher fixation stability is achieved when the scaphoid is fixated perpendicular to the fracture. In transverse waist fractures, a centrally placed screw will also be perpendicular to the fracture, which explains the results of previous models.
目的:本研究的假设是,如先前所述,与沿舟骨长轴置入螺钉相比,垂直于骨折平面置入螺钉可能会实现急性舟骨骨折更稳定的固定。我们使用有限元分析模型,针对不同的骨折类型检验了这一假设。 方法:一名年轻男性完整舟骨的计算机断层扫描提供了所有骨折模型的数据集。我们根据赫伯特分类法,使用半自动分割技术创建了3种简单骨折构型的三维计算机模型:斜形、腰部横行和近端骨折。每种骨折类型都使用有限元分析其对两种虚拟固定方式的生物力学反应:垂直于骨折平面置入的螺钉或沿舟骨长轴中心置入的螺钉。我们测量了骨折平面处的位移(以毫米为单位)和螺钉螺纹处的应变(以毫帕斯卡为单位)。 结果:与长轴螺钉相比,垂直螺钉在骨折平面处测得的位移明显更小,尤其是在斜形骨折类型中:(1) 赫伯特B1型斜形骨折,垂直螺钉的平均位移为0.05毫米(±0.03),长轴螺钉为0.28毫米(±0.05);(2) B2型腰部横行骨折,垂直螺钉的平均位移为0.06毫米(±0.03),长轴螺钉为0.18毫米(±0.06);(3) B3型近端骨折,垂直螺钉的平均位移为0.07毫米(±0.01),长轴螺钉为0.28毫米(±0.011)。垂直于骨折置入螺钉时测得的应变更高。 结论:根据该模型,当舟骨垂直于骨折进行固定时,可实现更高的固定稳定性。在腰部横行骨折中,中心置入的螺钉也会垂直于骨折,这解释了先前模型的结果。
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