Dueland R T, Berglund L, Vanderby R, Chao E Y
Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, USA.
Vet Surg. 1996 Sep-Oct;25(5):386-96. doi: 10.1111/j.1532-950x.1996.tb01432.x.
Using standard material testing techniques (bending stiffness, torsional stiffness, and maximum torque to failure or yield torque), the structural properties of interlocking nails (IN), canine femora, and IN/femur constructs were determined. Specimens that were tested included: 6 and 8 mm diameter IN with 5 to 10 screw holes (n = 18), and intact canine femora (n = 10), which also, with an IN inserted, formed the intact construct (IC) group, (n = 10). Specimens in the IC group were first tested with an 8 mm diameter IN with zero screws, followed by one and two screws (4.5 mm diameter) in the proximal and distal femur. A fracture model construct (FMC), (n = 14), consisting of a transverse femoral osteotomy with a 3 mm gap, was used with either 6 mm or 8 mm IN. In the 6 mm FMC, one and two 3.5 mm screws were used sequentially in the proximal and distal femoral segment. In the 8 mm FMC, one and two 3.5 mm screws and one and two 4.5 diameter screws were used similarly. When bending forces were applied parallel to IN screw holes, mean IN stiffness was 20% less than with forces perpendicular to the holes (n = 18), (P < .05). Eight-millimeter IN were 220% stiffer in torsion and 270% stiffer in bending than 6 mm IN (P < .05). Six-millimeter IN had approximately 32% of the bending stiffness and torsional stiffness of intact femurs (P < .05). Eight-millimeter IN had 93% and 79% of the bending stiffness and torsional stiffness, respectively, of intact femurs. Intact femur constructs (8 mm IN with four, 4.5 mm screws) had 147% of the bending stiffness (P < .05), and similar torsional stiffness and maximum torque, as intact femora (P > .05). The mean values of 6 mm FMC with four screws (3.5 mm) were 21% and 33% in torsional stiffness and bending stiffness, respectively, of intact femora values. When tested in torsion, 8 mm FMC failed by bone fracture; 6 mm FMC, in contrast, underwent plastic deformation. In comparing FMC stabilized with an 8 mm IN with two screws (4.5 mm diameter) in each bone segment, to intact femurs, the maximum torque was similar, FMC torsional stiffness was 40% (P < .05), and FMC bending stiffness was 65% (P < .05). These 8 mm FMC percentages are comparable to human IN fracture model construct values, indicating that the 8 mm IN/four screw construct should provide adequate stabilization for many canine diaphyseal femoral fractures.
采用标准材料测试技术（弯曲刚度、扭转刚度以及破坏时的最大扭矩或屈服扭矩），测定了交锁髓内钉（IN）、犬股骨以及IN/股骨结构的结构特性。所测试的样本包括：直径6毫米和8毫米、带有5至10个螺孔的IN（n = 18），以及完整的犬股骨（n = 10），后者在插入IN后还形成了完整结构（IC）组（n = 10）。IC组样本首先使用直径8毫米、无螺钉的IN进行测试，随后在股骨近端和远端分别插入1枚和2枚（直径4.5毫米）螺钉进行测试。骨折模型结构（FMC）（n = 14）由股骨横向截骨、骨间隙为3毫米构成，使用6毫米或8毫米的IN。在6毫米FMC中，股骨近端和远端节段依次使用1枚和2枚3.5毫米螺钉。在8毫米FMC中，同样依次使用1枚和2枚3.5毫米螺钉以及1枚和2枚直径4.5毫米的螺钉。当平行于IN螺孔施加弯曲力时，IN的平均刚度比垂直于螺孔施加力时小20%（n = 18），（P <.05）。8毫米的IN在扭转时刚度比6毫米的IN大220%，在弯曲时刚度大270%（P <.05）。6毫米的IN的弯曲刚度和扭转刚度分别约为完整股骨的32%（P <.05）。8毫米的IN的弯曲刚度和扭转刚度分别为完整股骨的93%和79%。完整股骨结构（8毫米IN加4枚4.5毫米螺钉）的弯曲刚度为完整股骨的147%（P <.05），扭转刚度和最大扭矩与完整股骨相似（P >.05）。带有4枚（3.5毫米）螺钉的6毫米FMC的扭转刚度和弯曲刚度的平均值分别为完整股骨值的21%和33%。在扭转测试中，8毫米FMC因骨折而失效；相比之下，6毫米FMC发生了塑性变形。将每个骨段用2枚（直径4.5毫米）螺钉固定的8毫米IN稳定的FMC与完整股骨进行比较，最大扭矩相似，FMC的扭转刚度为40%（P <.05），弯曲刚度为65%（P <.05）。这些8毫米FMC的百分比与人类IN骨折模型结构的值相当，表明8毫米IN/4枚螺钉结构应为许多犬股骨干骨折提供足够的稳定性。
