Department of Orthopedics and Trauma Surgery, Medical Center, Faculty of Medicine, Albert-Ludwigs University of Freiburg, Germany; G.E.R.N. Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Medical Center, Faculty of Medicine, Albert-Ludwigs University of Freiburg, Germany.
G.E.R.N. Tissue Replacement, Regeneration & Neogenesis, Department of Orthopedics and Trauma Surgery, Medical Center, Faculty of Medicine, Albert-Ludwigs University of Freiburg, Germany.
J Shoulder Elbow Surg. 2021 Feb;30(2):365-372. doi: 10.1016/j.jse.2020.06.007. Epub 2020 Jun 30.
Biodegradable implants have gained increasing importance for the fixation of simple displaced radial head fractures to supersede implant removal and to minimize cartilage destruction. Commonly used polylactide pins still lead to higher rates of secondary loss of reduction compared with metal implants. Alternatively, implants made from a magnesium alloy meanwhile are available in a pin design that hypothetically could perform better than polylactide pins. Because biomechanical data of clinical applications are lacking, the goal of the present study was to biomechanically compare magnesium pins to polylactide pins using a Mason type II radial head fracture model.
Fourteen pairs of fresh-frozen human cadaver radii with a standardized Mason type II radial head fracture were stabilized either by two 2.0-mm polylactide pins (PPs) or two 2.0-mm magnesium pins (MPs). Biomechanical in vitro testing was conducted as 10 cycles of static loading at 0.1 Hz axially and transversally between 10 and 50 N. Afterward, loosening was tested by dynamic load changes at 4 Hz up to 100,000 cycles. Early fracture displacement was measured after 10,000 cycles. Afterward, maximum loads were raised every 10,000 cycles by 15 N until construct failure, which was defined as fracture displacement ≥2 mm.
MP osteosynthesis showed a tendency toward higher primary stability on both axial (MP: 0.19 kN/mm, PP: 0.11 kN/mm; P = .068) and transversal loading (MP: 0.11 kN/mm, PP: 0.10 kN/mm; P = .068). Early fracture displacement was significantly higher following PP osteosynthesis (MP: 0.3 mm, PP: 0.7 mm; P = .030). The superiority of MP was also significant during cyclic loading, represented in a higher failure cycle (MP: 30,684, PP: 5113; P = .009) and in higher failure loads (MP: 95 N, PP: 50 N; P = .024).
According to our findings, in simple radial head fractures, osteosynthesis with magnesium pins show superior biomechanical properties compared with fractures treated by polylactide pins. Prospective investigations should follow to evaluate clinical outcomes and resorption behavior.
可生物降解的植入物对于固定简单移位的桡骨头骨折变得越来越重要，以取代植入物的去除并最大程度地减少软骨破坏。与金属植入物相比，常用的聚乳酸钉仍导致更高的复位丢失率。另一方面，目前可提供一种由镁合金制成的钉设计的植入物，理论上这种植入物的性能可能优于聚乳酸钉。由于缺乏临床应用的生物力学数据，本研究的目的是使用 Mason Ⅱ型桡骨头骨折模型对镁钉和聚乳酸钉进行生物力学比较。
将 14 对带有标准化 Mason Ⅱ型桡骨头骨折的新鲜冷冻人尸体桡骨通过两根 2.0mm 的聚乳酸钉（PP）或两根 2.0mm 的镁钉（MP）固定。生物力学体外测试包括 0.1Hz 轴向和横向 10 至 50N 之间的 10 个循环静态加载。然后，通过 4Hz 的动态载荷变化测试松动，直至 100,000 次循环。在 10,000 次循环后测量早期骨折位移。然后，每 10,000 次循环增加 15N 的最大载荷，直到结构失效，定义为骨折位移≥2mm。
MP 内固定在轴向（MP：0.19kN/mm，PP：0.11kN/mm；P=0.068）和横向加载（MP：0.11kN/mm，PP：0.10kN/mm；P=0.068）时均显示出较高的初始稳定性。PP 内固定后的早期骨折位移明显更高（MP：0.3mm，PP：0.7mm；P=0.030）。在循环加载中，MP 的优势也很明显，表现为更高的失效循环（MP：30,684，PP：5113；P=0.009）和更高的失效载荷（MP：95N，PP：50N；P=0.024）。
根据我们的发现，在简单的桡骨头骨折中，与聚乳酸钉治疗的骨折相比，镁钉内固定具有更好的生物力学性能。应进行前瞻性研究以评估临床结果和吸收行为。
