Systemic Exposure in Large and Small Diameter Metal-Metal Hip Replacements - Hena Ziaee, 2007
In this lecture, Biomedical Scientist Hena Ziaee BSc (Hons) discusses systemic metal exposure in large and small diameter metal-on-metal Total Hip Replacements (THRs).
The Metasul metal on metal bearing was introduced as a small diameter Total Hip Replacement (THR) nearly twenty years ago. The wear rates from these metal-on-metal devices were much lower than the conventional metal on polyethylene Total Hip Replacements.
Modern large diameter metal-on-metal bearings were introduced as Hip Resurfacings. These bearings worked very well and seemed to bridge the gap for young patients with hip disease and the desire for an active lifestyle.
Advantages of the large diameter metal-on-metal Total Hip Replacement include a reduced dislocation rate, low wear rate and an increased range of motion before impingement.
A study was undertaken to test the metal ion levels in large diameter metal-on-metal Total Hip Replacements in comparison to small diameter bearings. Systemic exposure was analysed with whole blood samples and urine measurements taken at twelve months post-op. The samples were analysed by High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICPMS).
The difference between the mean whole blood cobalt and chromium levels in the small diameter THRs and the large diameter THRs are not statistically significant. Daily urinary output of cobalt and chromium in both THR groups were also in the same range and without significant mean difference.
