Garcia-Lopez Edgar, Siu Jeremy Wafong, Kwong Jeffrey W, Kamal Robin N, Schroeder Nicole, Shapiro Lauren M
Department of Orthopedic Surgery, University of California, San Francisco, CA.
Department of Orthopedic Surgery, University of California, San Francisco, CA.
J Hand Surg Am. 2024 Oct 1. doi: 10.1016/j.jhsa.2024.08.009.
Although metacarpal fractures are typically managed nonoperatively, when surgical management is indicated, metacarpal fractures are commonly treated with crossed Kirschner wires (K-wires), which may limit early range of motion. Intramedullary implants are increasing in use with the potential advantage of early range of motion; however, stability in oblique metacarpal neck fractures remains a theoretical concern. The purpose of this study was to determine the biomechanical stability of noncompressive intramedullary fixation for oblique metacarpal neck fractures compared with crossed K-wire fixation.
The index, long, and small metacarpals were harvested from three matched pairs of fresh-frozen cadavers. Oblique fractures at the metadiaphyseal region were created in each metacarpal. Each metacarpal was randomized to noncompressive, threaded intramedullary nail fixation or fixation with two crossed K-wires. Specimens were mounted in a Materials Testing System load frame and axially loaded until failure. Load to failure (LTF), stiffness, and load to 2 mm displacement were calculated from load-displacement curves. Differences in peak LTF, stiffness, and load to 2 mm displacement between noncompressive intramedullary fixation and crossed K-wire fixation were evaluated.
The noncompressive intramedullary fixation cohort had a significantly higher LTF (1,190.9 ± 534.7 N vs 297.0 ± 156.0 N) and stiffness (551.3 ± 164.6 N/mm vs 283.0 ± 194.5 N/mm) when compared with the crossed K-wire fixation cohort. Load at 2 mm displacement was greater in the noncompressive intramedullary fixation cohort compared with crossed K-wire fixation (820.5 ± 203.9 vs 514.1 ± 259.6).
For oblique metadiaphyseal metacarpal fractures, noncompressive intramedullary fixation provides a biomechanically superior construct under axial loading in terms of LTF, stiffness, and load to 2 mm of displacement compared with crossed K-wire fixation.
Noncompressive intramedullary nails may be an alternative to K-wire fixation for the treatment of oblique metadiaphyseal metacarpal fractures.
虽然掌骨骨折通常采用非手术治疗，但在需要手术治疗时，掌骨骨折常用交叉克氏针（K 针）治疗，这可能会限制早期活动范围。髓内植入物的使用越来越多，具有早期活动范围的潜在优势；然而，斜形掌骨颈骨折的稳定性仍是一个理论上的问题。本研究的目的是确定与交叉 K 针固定相比，非加压髓内固定治疗斜形掌骨颈骨折的生物力学稳定性。
从三对匹配的新鲜冷冻尸体上获取示指、中指和小指掌骨。在每个掌骨的骨干中段区域制造斜形骨折。每个掌骨随机分为非加压螺纹髓内钉固定或两根交叉 K 针固定。将标本安装在材料测试系统加载框架中并轴向加载直至失效。根据载荷 - 位移曲线计算失效载荷（LTF）、刚度和位移 2 mm 时的载荷。评估非加压髓内固定和交叉 K 针固定之间在峰值 LTF、刚度和位移 2 mm 时的载荷差异。
与交叉 K 针固定组相比，非加压髓内固定组的 LTF 显著更高（1190.9±534.7 N 对 297.0±156.0 N），刚度也更高（551.3±164.6 N/mm 对 283.0±194.5 N/mm）。与交叉 K 针固定相比،非加压髓内固定组在位移 2 mm 时的载荷更大（820.5±203.9 对 514.1±259.6）。
对于斜形掌骨干骨折，与交叉 K 针固定相比，非加压髓内固定在轴向加载下，在 LTF、刚度和位移 2 mm 时的载荷方面提供了生物力学上更优越的结构。
非加压髓内钉可能是治疗斜形掌骨干骨折时 K 针固定的一种替代方法。
