Denver Health/University of Colorado, Denver, CO, USA.
J Orthop Trauma. 2010 Apr;24(4):207-11. doi: 10.1097/BOT.0b013e3181bdd1da.
The purpose of this study was to compare the biomechanical behavior of using two versus three locking screws per bone segment in a cadaveric humerus fracture gap model.
Six matched pairs of elderly osteoporotic fresh-frozen human cadaveric humerii were used. An eight-hole locking compression plate was placed posteriorly on the humeral shaft and secured with either four or six bicortical locking screws. A 5-mm middiaphyseal gap osteotomy was created to simulate a comminuted fracture without bony contact. Specimens were tested in offset axial compression, four-point anteroposterior bending, four-point medial-lateral bending, and torsion. After the initial testing in each of these modalities, the constructs were cyclically loaded in torsion and again tested in the four loading modalities. Lastly, the fixation constructs were then tested to failure in torsion.
There were no significant differences in stiffness between the group fixed with two screws per segment and the group fixed with three screws per segment. The peak torque to failure was higher in the four-screw construct compared with the six-screw construct. The mean torque to failure was 23.5 +/- 3.7 Nm in the construct with two locking screws per segment compared with 20.4 +/- 2.8 Nm in the construct with three locking screws per segment (P = 0.030).
The addition of a third screw in the locked plate construct did not add to the mechanical stability in axial loading, bending, or torsion. In testing to failure, the addition of a third screw resulted in lower load to failure.
本研究旨在比较在尸体肱骨干骨折间隙模型中，每骨段使用 2 枚与 3 枚锁定螺钉的生物力学行为。
使用 6 对匹配的老年骨质疏松性新鲜冷冻人肱骨干。在后侧肱骨干上放置 8 孔锁定加压钢板，并使用 4 或 6 枚皮质锁定螺钉固定。创建一个 5mm 的骨干中部间隙截骨术来模拟无骨接触的粉碎性骨折。标本在偏心轴向压缩、四点前后弯曲、四点内外弯曲和扭转中进行测试。在这些模式中的每种模式的初始测试后，将构建物在扭转中循环加载，然后再次在四种加载模式中进行测试。最后，在扭转中对固定构建物进行失效测试。
每节固定 2 枚螺钉的组与每节固定 3 枚螺钉的组之间的刚度没有显著差异。四螺钉组的峰值破坏扭矩高于六螺钉组。每节固定 2 枚锁定螺钉的构建物的平均破坏扭矩为 23.5 +/- 3.7 Nm，而每节固定 3 枚锁定螺钉的构建物的平均破坏扭矩为 20.4 +/- 2.8 Nm（P = 0.030）。
在锁定钢板构建物中增加第三枚螺钉不会增加轴向加载、弯曲或扭转的机械稳定性。在失效测试中，增加第三枚螺钉会导致更低的失效负载。
