Wallace Melissa, Johnson David B, Pierce William, Iobst Christopher, Riccio Anthony, Wimberly R Lane
Department of Orthopaedic Surgery, Texas Scottish Rite Hospital, Dallas, TX.
Department of Orthopedic Surgery, Nationwide Children's Hospital, Columbus, OH.
J Pediatr Orthop. 2019 Mar;39(3):e210-e215. doi: 10.1097/BPO.0000000000001270.
We assessed the effect on the torsional stability by different pin diameters and varied pin configurations in a biomechanical supracondylar humerus fracture model.
After scanning a model of a pediatric humerus, the image was imported into software. Variable pin trajectories were planned. Acrylonitrile butadiene styrene plastic models were 3-dimensionally printed with predetermined pin trajectories. Models were osteotomized and potted with a polyurethane resin. Five-pin configurations were designed to test coronal and sagittal patterns of pin placement. Each included 3 lateral pins and a medial pin. Pin diameters of 1.6, 2.0, and 2.4 mm were tested in all configurations. Three models for each pin diameter/configuration were tested to ensure uniformity. Stability of the construct was tested to determine the torque needed to deflect the osteotomy 10 degrees in internal/external rotation. Each model was tested 3 times.
In all models/configurations, the 2.4 mm pin diameter was statistically stiffer than 1.6 mm diameter pins; this lost statistical significance in certain patterns when comparing 2.0- and 2.4-mm pins. When comparing a divergent to a parallel configuration in the coronal plane, there was no significant difference in stability when pin diameter or number were controlled. The convergent pin configuration was, in general, the least stable pattern. Use of a medial pin conferred statistically significant stiffness throughout most models as demonstrated with pin deletion. Use of 2 pins was significantly less stiff than most 3-pin models.
Larger pin diameters confer greater stiffness among all patterns. The use of 3 lateral and 1 medial pin was not statistically different than 2 lateral and 1 medial pin in our models. Both patterns were stiffer than 3 lateral pins only or other fewer pin constructs. The alignment of pins in the sagittal plane did not affect overall construct stiffness.
我们在一个生物力学肱骨髁上骨折模型中评估了不同直径的克氏针以及不同克氏针构型对扭转稳定性的影响。
扫描一个儿童肱骨模型后，将图像导入软件。规划可变的克氏针轨迹。按照预定的克氏针轨迹对丙烯腈-丁二烯-苯乙烯塑料模型进行三维打印。将模型截骨并用聚氨酯树脂封装。设计了五种克氏针构型来测试冠状面和矢状面的克氏针置入模式。每种构型都包括3根外侧克氏针和1根内侧克氏针。在所有构型中测试1.6、2.0和2.4毫米的克氏针直径。每种克氏针直径/构型测试三个模型以确保一致性。测试固定结构的稳定性，以确定使截骨处在内旋/外旋时偏移10度所需的扭矩。每个模型测试3次。
在所有模型/构型中，2.4毫米直径的克氏针在统计学上比1.6毫米直径的克氏针更硬；在比较2.0毫米和2.4毫米克氏针时，在某些模式下这种差异失去统计学意义。在冠状面比较发散构型和平行构型时，当克氏针直径或数量得到控制时，稳定性没有显著差异。一般来说，汇聚克氏针构型是最不稳定的模式。如通过去除克氏针所证明的，在大多数模型中使用内侧克氏针在统计学上赋予了显著的硬度。使用2根克氏针的硬度明显低于大多数3根克氏针的模型。
在所有模式中，较大直径的克氏针具有更大的硬度。在我们模型中，使用3根外侧和1根内侧克氏针与使用2根外侧和1根内侧克氏针在统计学上没有差异。这两种模式都比仅使用3根外侧克氏针或其他较少克氏针结构更硬。矢状面克氏针的排列不影响整体固定结构的硬度。
