Caja V L, Larsson S, Kim W, Chao E Y
Orthopedic Biomechanics Laboratory, Department of Orthopedics, Mayo Clinic/Mayo Foundation, Rochester, MN.
Clin Orthop Relat Res. 1994 Dec(309):257-66.
Six configurations of the Monticelli-Spinelli external fixator were tested for axial compression, bending, and torsion. The ring wire clamp unit was separately tested under repeated cyclic loading and retightening of the clampnuts. The configurations studied were the following: 3 standard (4-ring and 3-ring with 5-mm between the wires and 3-ring with 40 mm between the wires); and 3 hybrid (3-ring and 1 pin, and 2-ring and 2 pins with the rings either placed closer or distant to the fracture). For each configuration, 5 frames were constructed. Axial stiffness was nonlinear for both fixator types. Four-ring fixators and 2-ring 2-pin fixators had similar stiffness, yet were stiffer than 3-ring configurations. Anteroposterior bending stiffness was highest in the 4-ring configurations, whereas oblique bending for standard fixators was similar to lateral bending stiffness for the hybrid configurations. Torsion was higher in the 4-ring construction and in hybrid frames compared to the standard 3-ring frames. For the ring wire clamp unit, stiffness increased and hysteresis diminished after each retightening of the clampnuts because of the increase of contact between clamps and ring. The hybrid configurations provide an alternative that enables more simple configurations with less transfixing elements and sufficient stiffness.
对Monticelli-Spinelli外固定器的六种构型进行了轴向压缩、弯曲和扭转测试。环钢丝夹单元在反复循环加载和拧紧螺母的情况下单独进行测试。所研究的构型如下：3种标准构型（4环、钢丝间距5毫米的3环和钢丝间距40毫米的3环）；以及3种混合构型（3环和1根针，以及2环和2根针，环与骨折处的距离较近或较远）。每种构型制作5个框架。两种固定器类型的轴向刚度均呈非线性。四环固定器和二环双针固定器具有相似的刚度，但比三环构型更硬。前后弯曲刚度在四环构型中最高，而标准固定器的斜向弯曲与混合构型的侧向弯曲刚度相似。与标准三环框架相比，四环结构和混合框架的扭转更大。对于环钢丝夹单元，由于夹钳与环之间接触增加，每次拧紧螺母后刚度增加，滞后减小。混合构型提供了一种替代方案，能够以更少的穿针元件和足够的刚度实现更简单的构型。
