Yamanaka Kenta, Mori Manami, Yamazaki Ken, Kumagai Ruriko, Doita Minoru, Chiba Akihiko
*Institute for Materials Research, Tohoku University, Sendai, Japan †Department of Materials and Environmental Engineering, Sendai National College of Technology, Natori, Japan; and ‡Department of Orthopedic Surgery, School of Medicine, Iwate Medical University, Morioka, Japan.
Spine (Phila Pa 1976). 2015 Jul 1;40(13):E767-73. doi: 10.1097/BRS.0000000000000881.
Retrieval analysis of 2 Ti-6Al-4V alloy rods that fractured after spinal instrumentation surgery.
To determine the mechanism that underlies fractures of Ti-6Al-4V alloy rods after spinal instrumentation surgery from a materials science viewpoint.
Rod failures after spinal instrumentation surgery are often reported and many case-based studies have been published. However, the details of the mechanism that underlies the fractures have not yet been fully elucidated.
Two patients, a 71-year-old female and an 11-year-old male, underwent radiography and removal of their fractured rods. The latter patient had been treated using the growing-rod method. Metallurgical failure analysis of the retrieved rods was conducted, and material properties were compared between the unused and fractured rods.
The microstructures and mechanical properties of the Ti-6Al-4V alloy rods that failed after spinal instrumentation surgery were similar to those of unused rods. Analysis of the fracture surfaces clearly identified fatigue cracking in both cases that would have lowered the resistance of the rods to failures caused by external stresses. Shot blasting the surfaces of Ti-6Al-4V alloy rods and bending the rods to fit particular contours, which is always conducted during spinal instrumentation surgery, probably introduced fatigue cracking because the alloy is highly notch sensitive.
Improvements should be made to rod design and/or rod material, because the fatigue resistance of titanium alloys is intrinsically lower than that of other commercially available rod materials, including cobalt-chromium alloys. These imperfections may have greater consequences for the growing-rod method and pseudarthrosis, where the rods are not completely fixed, and they subsequently suffer from severe long-arm moments.
N/A.
对2根在脊柱内固定手术后发生断裂的Ti-6Al-4V合金棒进行检索分析。
从材料科学角度确定脊柱内固定手术后Ti-6Al-4V合金棒断裂的潜在机制。
脊柱内固定手术后棒材失效的情况经常被报道，并且已经发表了许多基于病例的研究。然而，骨折潜在机制的细节尚未完全阐明。
两名患者，一名71岁女性和一名11岁男性，接受了X线检查并取出了断裂的棒材。后一名患者采用生长棒方法进行治疗。对取出的棒材进行了冶金失效分析，并比较了未使用棒材和断裂棒材的材料性能。
脊柱内固定手术后失效的Ti-6Al-4V合金棒的微观结构和力学性能与未使用的棒材相似。对断裂表面的分析清楚地确定了两种情况下的疲劳裂纹，这会降低棒材对外力引起的失效的抵抗力。对Ti-6Al-4V合金棒材表面进行喷丸处理并将棒材弯曲以适应特定轮廓，这在脊柱内固定手术中总是会进行，可能会引入疲劳裂纹，因为该合金对缺口高度敏感。
应改进棒材设计和/或棒材材料，因为钛合金的抗疲劳性本质上低于其他市售棒材材料，包括钴铬合金。这些缺陷对于生长棒方法和假关节可能会产生更大的影响，在这些情况下棒材没有完全固定，随后会承受严重的长臂力矩。
无。
