Abstract
Introduction: The wear particles produced from the metal-on-metal hip prosthesis causes measurable rise of metal ion levels in the patient’s body fluids. Wear of the bearing is directly related to its use. The goal of this study is to test two hypotheses. Firstly, that exercise causes increased wear particles in vivo which can cause immediate measurable rise in the serum metal ion levels. Secondly, that this rise in metal ion level is different for different types of bearings.
Material and Methods: Eighteen participants were allocated to four different groups i.e. Birmingham Hip Resurfacing prosthesis group, Cormet 2000 resurfacing prosthesis group, Thrust plate prosthesis group (28mm metasul articulation) and group four with out any metal work. Blood samples were taken immediately before, immediately after and one hour after exercise. Plasma cobalt and chromium was determined using Inductively-Coupled-Plasma-Mass-Spectrometry and Dynamic-reaction-cell respectively with detection limit of 2nmol/l each.
Results: The four patient groups were comparable. A significant increase (p< 0.005) in serum cobalt and chromium of 13% and 11% respectively, was noticed after the exercise. Rise of cobalt levels in patients with a resurfacing MOM was 8.5 times (BHR group) and 6.5 times (Cormet group) larger than in those with a Metasul (p=0.021 and p=0.047). Neither rise of metal levels nor baseline levels correlated with any other factor (p> 0.27).
Discussion: Physiologic exercise causes immediate detectable rise in the serum metal ion levels. The increase is predominantly related to the size of the bearing surface. Exercise-related-cobalt-rise could be used to assess the tribology of the different metal on metal designs in vivo for future research
Correspondence should be addressed to The Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
