Rothenfluh Esin, Jain Sambhav, Taylor William R, Hosseini Nasab Seyyed Hamed
Department of Plastic and Hand Surgery, Inselspital, Bern University Hospital, 3010 Bern, Switzerland.
Laboratory for Movement Biomechanics, Department of Health Sciences and Technology, ETH Zürich, 8092 Zürich, Switzerland.
Bioengineering (Basel). 2025 Jul 22;12(8):790. doi: 10.3390/bioengineering12080790.
The scaphoid is the most commonly fractured carpal bone. Headless compression screws became the gold standard for fixation, but the ideal screw diameter remains debated. This study investigates the relative benefit of using a larger screw diameter to improve stability in typical scaphoid fractures. It also examines the effects of preload and screw length on mechanical behaviour. A finite element (FE) model of a mid-waist scaphoid fracture was created. Screws from Medartis (1.7 mm, 2.2 mm, and 3.0 mm diameter; 23 mm length) were placed along the longitudinal axis. Boundary and loading conditions matched prior studies. Interfragmentary displacement (IFD) and von Mises stress were compared across screw sizes. The effects of screw length and preload were also evaluated. Maximum in-plane IFD was 2.08 mm (1.7 mm screw), 0.53 mm (2.2 mm), and 0.27 mm (3.0 mm). The 1.7 mm screw exceeded the scaphoid's average ultimate stress (60.51 MPa). Increasing preload reduced IFD, especially above 60 N. Screws longer than 1.5 times the mid-waist diameter offered no added benefit. Larger screws provide better biomechanical fracture stability. However, the gain from 2.2 mm to 3.0 mm is minor, while 1.7 mm screws lack sufficient strength. The 2.2 mm screw offers a good balance of stability and bone preservation, making it the preferred choice.
舟骨是最常发生骨折的腕骨。无头加压螺钉成为固定的金标准，但理想的螺钉直径仍存在争议。本研究探讨使用更大直径螺钉以提高典型舟骨骨折稳定性的相对益处。它还研究了预紧力和螺钉长度对力学行为的影响。创建了一个舟骨腰部骨折的有限元（FE）模型。将Medartis公司的螺钉（直径1.7毫米、2.2毫米和3.0毫米；长度23毫米）沿纵轴放置。边界条件和加载条件与先前的研究相匹配。比较了不同尺寸螺钉的骨折块间位移（IFD）和冯·米塞斯应力。还评估了螺钉长度和预紧力的影响。最大平面内IFD分别为2.08毫米（1.7毫米螺钉）、0.53毫米（2.2毫米）和0.27毫米（3.0毫米）。1.7毫米的螺钉超过了舟骨的平均极限应力（60.51兆帕）。增加预紧力可减少IFD，尤其是在60牛以上时。长度超过腰部直径1.5倍的螺钉没有额外益处。更大的螺钉提供更好的生物力学骨折稳定性。然而，从2.2毫米增加到3.0毫米的益处较小，而1.7毫米的螺钉强度不足。2.2毫米的螺钉在稳定性和骨质保留之间提供了良好的平衡，使其成为首选。
