Emory University, Department of Orthopedic Surgery, Atlanta, GA.
Emory University, Department of Orthopedic Surgery, Atlanta, GA.
J Hand Surg Am. 2024 Nov;49(11):1139.e1-1139.e7. doi: 10.1016/j.jhsa.2023.01.026. Epub 2023 Mar 11.
Interest in intramedullary metacarpal fracture fixation (IMFF) with screws is increasing. However, the optimal screw diameter for fracture fixation is not yet established. In theory, larger screws should be more stable, but there is concern about long-term sequelae of larger metacarpal head defects and extensor mechanism injury created during insertion as well as implant cost. Therefore, the purpose of this study was to compare different diameter screws for IMFF to a popular and more cost-effective alternative of intramedullary wiring.
Thirty-two cadaveric metacarpals were used in a transverse metacarpal shaft fracture model. Treatment groups consisted of IMFF with 3.0 × 60 mm, 3.5 x 60 mm, and 4.5 x 60 mm screws as well as 4 1.1-mm intramedullary wires. Cyclic cantilever bending was performed with the metacarpals mounted at 45° to simulate physiologic loading. Cyclical loading at 10, 20, and 30 N was performed to determine fracture displacement, stiffness, and ultimate force.
At 10, 20, and 30 N of cyclical loading, all screw diameters tested provided similar stability as measured by fracture displacement and were superior to the wire group. However, ultimate force under load to failure testing was similar between the 3.5- and 4.5-mm screws and superior to 3.0-mm screws and wires.
For IMFF, 3.0, 3.5, and 4.5-mm diameter screws provide adequate stability for early active motion and are superior to wires. When comparing the different screw diameters, 3.5- and 4.5-mm diameter screws offer similar construct stability and strength superior to the 3.0-mm diameter screw. Therefore, to minimize metacarpal head morbidity, smaller screw diameters may be preferable.
This study suggests that IMFF with screws is biomechanically superior to wires in cantilever bending strength in the transverse fracture model. However, smaller screws may be sufficient to permit early active motion while minimizing metacarpal head morbidity.
人们对髓内掌骨干骨折固定（IMFF）用螺钉的兴趣日益增加。然而，用于骨折固定的最佳螺钉直径尚未确定。理论上，较大的螺钉应该更稳定，但人们担心插入过程中较大的掌骨头缺陷和伸肌机制损伤以及植入物成本的长期后果。因此，本研究的目的是比较 IMFF 不同直径螺钉与更流行且更具成本效益的髓内钢丝的替代物。
32 个尸体掌骨用于横向掌骨干骨折模型。治疗组包括用 3.0×60mm、3.5x60mm 和 4.5x60mm 螺钉以及 4 根 1.1mm 髓内钢丝进行 IMFF。将掌骨安装在 45°以模拟生理负荷，进行周期性悬臂弯曲。在 10、20 和 30N 的循环加载下进行骨折位移、刚度和极限力的测试。
在 10、20 和 30N 的循环加载下，所有测试的螺钉直径在测量的骨折位移方面都提供了相似的稳定性，并且优于钢丝组。然而，在负载失效测试下的极限力，3.5-和 4.5mm 螺钉之间相似，且优于 3.0mm 螺钉和钢丝。
对于 IMFF，3.0、3.5 和 4.5mm 直径螺钉可提供足够的早期主动运动稳定性，优于钢丝。在比较不同的螺钉直径时，3.5-和 4.5mm 直径螺钉提供相似的结构稳定性，强度优于 3.0mm 直径螺钉。因此，为了最大限度地减少掌骨头病损，较小的螺钉直径可能更为理想。
本研究表明，在横向骨折模型中，髓内掌骨干骨折螺钉固定在悬臂弯曲强度方面优于钢丝固定。然而，较小的螺钉可能足以允许早期主动运动，同时最大限度地减少掌骨头病损。
