Correlation found between the angle of replacement joints and levels of metal ions

The Journal of Bone and Joint Surgery, British Volume published more ground breaking research on the subject of metal-on-metal hip resurfacings and metal ion levels. October’s article investigates the link between the angle of the replacement joint and blood levels of chromium and cobalt ions.

The study found "significantly higher levels of metal ions in patients with steeply-inclined components". While the long term consequences of the release of these ions are currently unknown, "high concentrations of Co and Cr are toxic and are known to interfere with a number of biological functions". The release of ions is caused by wearing of the metal-on-metal component and yet "no correlation was found between the level of activity and the concentration".

In addition, the steeper the inclination of the acetabular component the higher the concentration of ions, most especially in women, and therefore the authors recommend that "surgeons need to be aware of the internal arc angle of the acetabular component…and should ensure that these are never more than 55º open".

(Source: Journal of Bone and Joint Surgery: British Editorial Society of Bone and Joint Surgery: October 2008)