C Department of Orthopaedics, Roger Salengro Hospital, Lille 2 University, Lille University Teaching Hospital Center, 59037 Lille cedex, France.
Orthop Traumatol Surg Res. 2009 Oct;95(6):443-6. doi: 10.1016/j.otsr.2009.07.003. Epub 2009 Sep 8.
Hard-on-hard bearings for total hip replacement may require a modular acetabular inlay for which polyethylene is often used in a sandwich-type configuration. However, differences in the elastic modulus of the materials make fixation of this metal insert uncertain. The aim of this study is to report a case of bilateral separation of the metal insert from the polyethylene sandwich in a metal-on-metal bearings prosthesis.
A bilateral total hip arthroplasty was performed in two operations, four months apart, in a 53-year-old woman following a corticosteroid-induced osteonecrosis. The total hip replacement system included a cementless stem, and a press-fit hemispheric cup containing a polyethylene sandwich with a metallic insert (Sikomet).
Three years later, the patient consulted because of abnormal noise in her right hip which appeared normal on conventional X-ray. Three months later she consulted again for persistent noise. Separation of the metal insert from the polyethylene sandwich was diagnosed and an acetabular revision was performed selecting a metal-on-polyethylene articulation system. The postoperative course, for this revision, was uneventful, but the patient returned with the similar symptoms in her left hip four months later, resulting in the same type of revision. During the revisions, osteolysis secondary to metallosis was diagnosed, requiring synovectomy and acetabular reconstruction with morcelized allograft impaction. The left side postoperative course included three dislocations in nine months which were conservatively treated and have not since recurred.
This is the first reported case recording an almost simultaneous bilateral dissociation of a hard-on-hard inlay from its polyethylene sandwich. This bilateral case suggests that the fixation of the metal insert inside the polyethylene was probably defective. This case is also a reminder that mechanical complications (separation, implant fracture) should be searched for in presence of any abnormal noise occurring after hard-on-hard bearings prosthetic implantation. This confirms the necessity of periodical follow-up of hip arthroplasties and the importance of knowing their radiological features. The low carbon content of the Sikomet bearing may have been the cause of this failure by increasing frictional torque on the bearing surface, causing metallosis which has already been described in the literature in this type of hip replacement system.
全髋关节置换中的硬对硬轴承可能需要一个模块化的髋臼内衬，通常在三明治结构中使用聚乙烯。然而，由于材料的弹性模量不同，这种金属嵌体的固定效果并不确定。本研究旨在报告一例金属对金属轴承假体中聚乙烯三明治金属嵌体双侧分离的病例。
一名 53 岁女性因皮质激素诱导的骨坏死接受了两次手术，分别在四个月内进行双侧全髋关节置换术。全髋关节置换系统包括一个非骨水泥的股骨柄和一个压配半球形髋臼杯，其中包含一个聚乙烯三明治和一个金属嵌体（Sikomet）。
三年后，患者因右髋关节异常响声就诊，常规 X 线片未见异常。三个月后，她再次因持续的响声就诊。诊断为金属嵌体从聚乙烯三明治中分离，并进行了髋臼翻修，选择了金属对聚乙烯关节系统。这次翻修的术后过程顺利，但四个月后，患者因左侧髋关节出现类似症状而再次就诊，需要进行同样的翻修。在翻修过程中，诊断为金属溶解引起的骨溶解，需要进行滑膜切除术和异体骨颗粒打压植骨髋臼重建。左侧术后九个月内发生了三次脱位，均采用保守治疗，未再复发。
这是首例报告的硬对硬嵌体几乎同时从其聚乙烯三明治中双侧分离的病例。这种双侧病例表明，金属嵌体在聚乙烯内的固定可能有缺陷。这个病例也提醒我们，在硬对硬轴承假体植入后出现任何异常响声时，应寻找机械并发症（分离、植入物断裂）。这证实了髋关节置换术需要定期随访的必要性，以及了解其影像学特征的重要性。Sikomet 轴承的低碳含量可能是导致这种失败的原因，它增加了轴承表面的摩擦力矩，导致金属溶解，这种情况在这种类型的髋关节置换系统中已有文献报道。
