University of Southern California, Los Angeles, USA.
Hand (N Y). 2022 Nov;17(6):1122-1127. doi: 10.1177/1558944720974111. Epub 2021 Jan 7.
Management of scaphoid nonunions with bone loss varies substantially. Commonly, internal fixation consists of a single headless compression screw. Recently, some authors have reported on the theoretical benefits of dual-screw fixation. We hypothesized that using 2 headless compression screws would impart improved stiffness over a single-screw construct.
Using a cadaveric model, we compared biomechanical characteristics of a single tapered 3.5- to 3.6-mm headless compression screw with 2 tapered 2.5- to 2.8-mm headless compression screws in a scaphoid waist nonunion model. The primary outcome measurement was construct stiffness. Secondary outcome measurements included load at 1 and 2 mm of displacement, load to failure for each specimen, and qualitative assessment of mode of failure.
Stiffness during load to failure was not significantly different between single- and double-screw configurations ( = .8). Load to failure demonstrated no statistically significant difference between single- and double-screw configurations. Using a qualitative assessment, the double-screw construct maintained rotational stability more than the single-screw construct ( = .029).
Single- and double-screw fixation constructs in a cadaveric scaphoid nonunion model demonstrate similar construct stiffness, load to failure, and load to 1- and 2-mm displacement. Modes of failure may differ between constructs and represent an area for further study. The theoretical benefit of dual-screw fixation should be weighed against the morphologic limitations to placing 2 screws in a scaphoid nonunion.
伴有骨缺损的舟状骨骨不连的处理方法差异很大。通常，内固定包括单一无头加压螺钉。最近，一些作者报告了双螺钉固定的理论优势。我们假设使用 2 枚无头加压螺钉会比单螺钉结构提供更好的刚度。
使用尸体模型，我们比较了在舟状骨腰部骨不连模型中，单一锥形 3.5 至 3.6mm 无头加压螺钉与 2 个锥形 2.5 至 2.8mm 无头加压螺钉的生物力学特性。主要的测量结果是结构的刚度。次要的测量结果包括在 1mm 和 2mm 位移时的载荷、每个标本的失效载荷以及失效模式的定性评估。
在失效载荷时，单螺钉和双螺钉构型之间的刚度没有显著差异（ =.8）。单螺钉和双螺钉构型之间的失效载荷没有统计学上的显著差异。使用定性评估，双螺钉结构比单螺钉结构更能保持旋转稳定性（ =.029）。
在尸体舟状骨骨不连模型中，单螺钉和双螺钉固定结构在结构刚度、失效载荷以及 1mm 和 2mm 位移时的载荷方面表现相似。失效模式可能在不同的结构之间存在差异，这是进一步研究的一个领域。双螺钉固定的理论优势应该与在舟状骨骨不连中放置 2 枚螺钉的形态学限制进行权衡。
