ANCA Medical Centre, Ghent, Belgium.
Clin Orthop Relat Res. 2013 Feb;471(2):377-85. doi: 10.1007/s11999-012-2526-x.
The interpretation of metal ion concentrations and their role in clinical management of patients with metal-on-metal implants is still controversial.
QUESTIONS/PURPOSES: We questioned whether patients undergoing hip resurfacing with no clinical problems could be differentiated from those with clinical (pain, loss of function) and/or radiographic (component malpositioning, migration, bone loss), problems based on metal ion levels, and if there was a threshold metal level that predicted the need for clinical intervention. Furthermore, we asked if patient and implant factors differed between these functional groups.
We retrospectively identified 453 unilateral and 139 bilateral patients with ion measurements at minimum followup of 12 months (mean, 4.3 years; range, 1-12.9 years). Patients were designated as well functioning or poorly functioning based on strict criteria. The acceptable upper levels within the well-functioning group were determined from the 75th percentile plus 1.5× interquartile range. The sensitivity and specificity of these levels to predict clinical problems were calculated.
Well-functioning group ions were lower than the poorly functioning group ion levels. The acceptable upper levels were: chromium (Cr) 4.6 μg/L, cobalt (Co) 4.0 μg/L unilateral and Cr 7.4 μg/L, Co 5.0 μg/L bilateral. The specificity of these levels in predicting poor function was high (95%) and sensitivity was low (25%). There were more males in the well-functioning group and more females and smaller femoral components in the poorly functioning group.
Metal levels higher than these proposed safe upper limits can predict problems with metal-on-metal resurfacings and are important parameters in the management of at-risk patients.
Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
金属离子浓度的解读及其在金属对金属植入物患者临床管理中的作用仍存在争议。
问题/目的：我们质疑是否可以根据金属离子水平将无临床问题（疼痛、功能丧失）和/或影像学（部件错位、迁移、骨丢失）问题的髋关节表面置换患者与有临床问题的患者区分开来，以及是否存在预测临床干预需求的金属阈值水平。此外，我们还询问了这些功能组之间是否存在患者和植入物因素的差异。
我们回顾性地确定了 453 例单侧和 139 例双侧接受离子测量的患者，随访时间至少为 12 个月（平均 4.3 年；范围为 1-12.9 年）。根据严格标准，将患者指定为功能良好或功能不良。从 75 百分位加上 1.5×四分位距确定功能良好组的可接受上限。计算这些水平预测临床问题的灵敏度和特异性。
功能良好组的离子水平低于功能不良组的离子水平。可接受的上限为：单侧 Cr4.6μg/L，Co4.0μg/L；双侧 Cr7.4μg/L，Co5.0μg/L。这些水平预测功能不良的特异性很高（95%），敏感性很低（25%）。功能良好组中男性较多，功能不良组中女性和较小的股骨部件较多。
高于这些建议的安全上限的金属水平可以预测金属对金属表面置换的问题，并且是高危患者管理的重要参数。
二级，诊断研究。有关证据水平的完整描述，请参见作者指南。
