An implant fracture is an unusual reason for total hip arthroplasty (THA) revision; however, it may cause serious clinical complications. The stress in femoral stems may increase considerably with the loss of bone support around the implant, leading to implant failure. This paper investigates the main reasons for the in vivo fracture of a Ti6Al4V revision femoral ZMR stem. Various methods were used: examination of the patient’s by radiographies; optical emission spectrometry; and Scanning Electron Microscopy (SEM). The titanium (Ti) alloy was also characterized through optical microscopy and a Vickers hardness test was carried out. A finite element analysis (FEA) was conducted to evaluate the stress distribution occurring in the femoral stem revision under loading.

The chemical composition and microstructure of the prosthesis did not reveal any non-conformity. The SEM analysis revealed fretting damage near the crack initiation site and the fractured surfaces exhibited characteristic ratchet marks, poorly formed striations and a small final fracture area. The FEA showed a stress concentration located at the proximal–distal taper junction, with a smaller diameter, coinciding with the crack initiation site.

The conclusion was that fatigue failure was due to a lack of bone sustainability that increased the stress, associated with design characteristics that caused a localized concentration of stress, and these were potentialized by a fretting mechanism, leading to the failure.

植入物骨折是全髋关节置换术（THA）翻修的不寻常原因。但是，这可能会导致严重的临床并发症。随着植入物周围骨支撑的丢失，股骨柄中的应力可能会大大增加，从而导致植入物失效。本文探讨了Ti6Al4V修订型股骨ZMR茎在体内断裂的主要原因。使用了多种方法：通过射线照相检查患者的病情；发射光谱 和扫描电子显微镜（SEM）。还通过光学显微镜表征了钛（Ti）合金，并进行了维氏硬度测试。进行了有限元分析（FEA），以评估在负荷下股骨干翻修中发生的应力分布。

假体的化学成分和微观结构未发现任何不合格之处。SEM分析表明，裂纹萌生点附近的微动损伤和断裂表面表现出特征性的棘轮痕迹，不良的条纹形成和较小的最终断裂面积。有限元分析显示应力集中在近端至远端的锥形连接处，直径较小，与裂纹萌生部位一致。

结论是疲劳衰竭是由于缺乏骨骼的可持续性而增加了应力，而骨骼的可持续性与导致局部应力集中的设计特征有关，并且这些疲劳通过微动机制被潜在化，从而导致了疲劳。