Cobalt Chromium Toxicity Resource Center


Metal on metal (MoM) hip replacements and resurfacings are under increasing criticism because of high revision rates and poor patient outcomes. Metal on metal wear and corrosion particles causes adverse local tissue reactions (ALTR). ALTR is associated with elevated levels of metal ions, such as cobalt and chromium, in the blood, and pseudotumors.

Many metal on metal joints, like Stryker and Depuy, are recalled as a result of ALTR to metal on metal wear and corrosion particles. MoM hip replacement issues are correlated with the release of metal ions, metal on metal wear, and corrosion from the implant. Corrosion damage of femoral head-neck tapers and stem-neck junction are well-known sources for these issues. Recently, reports indicated the acetabular liner-shell taper as an additional source of corrosion and fretting wear. These sources are considered in vivo, “within the living”, metal corrosion products. This study focuses primarily on the liner-shell taper.

Data for the study was collected from 36 patients with MoM hips, and modular acetabular cups, undergoing revision surgery between 2011 and 2013. Twenty two percent (8 of the 36) cobalt-chromium alloy liners exhibited obvious and extensive corrosion of the liner-shell taper and material removal. Blood samples were collected from the patients to analyze the presence of cobalt and chromium metal ions. In addition, the liner taper junction was evaluated and scored for damage and severity of corrosion.

The articulating surfaces of metal on metal implants are possibly the main source of elevated metal ion levels. As aforementioned, the head-neck taper connection and wear at the articulating surface are also known to cause metal on metal corrosion, wear and elevated ion levels. The taper junctions of modular femoral heads cause corrosion product release. Corrosion product release results in ALTR and systemic toxicity from metal ion accumulation. The corrosion rates are similar between these taper junctions. Evidence suggests that liner-shell tapers and head-neck taper corrosion pose the same risk to patients.

In recent years, the use of MoM hips has significantly declined.  However, liner corrosion is a present concern for other implants where the modular acetabular shell and liner are joined by a taper junction.

Metal on metal corrosion from acetabular liner taper              Hip implant joints


Source: The Journal of Arthroplasty Corrosion on the Acetabular Liner Taper from Retrieved Modular Metal-on-Metal Total Hip Replacements

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