HIP UPDATE IN 2012 

Minerva Ortopedica e Traumatologica 2012 April;63(2):85-99

Copyright © 2012 EDIZIONI MINERVA MEDICA

language: English

Metal on metal bearing in total hip arthroplasty

Alghamdi A. ^{1, 2}, Lavigne M. ^{1, 2}, Vendittoli P. A. ^{1, 2}

¹ Department of Orthopedic Surgery, Maisonneuve-Rosemont Hospital, Montréal, QC, Canada; ² University of Montréal,, Montréal, QC, Canada

mplants with metal-on-metal articulation have been used in over 300,000 total hip replacements.Improved tribological properties of the new metal-on-metal bearings were the cornerstone in the successful of the current designs. Although the importance of each factor is not clear, recognized tribological key points are: reduced surface roughness, improved roundness, smaller clearance, harder CoCr alloy and higher carbon content. Variousclinical results were reported with up to 100% at 60 months (5 years mean follow up) to 93% at 120 months (10 years mean follow up) survival rate. However, lingering concerns about the biologic consequences of metal release including potential systemic and local effects as a consequence of chronic elevations in serum cobalt and chromium content and excessive metal debris production.The best method that has to be considered in order to reduce the metal ions levels is to reduce the bearing’s wear debris production.The minimal follow-up required for metal-on-metal THA might be 5 years based on 1% incidence of ARMD reported in the first 5 years. Radiographic analysis and metal ions level are considered to be the gold standard measures used in aiding the diagnosis of early implants failure and soft-tissue complications, even in asymptomatic patient.The controversy now a day is about when to intervene, when soft tissue changes are found, and weather early intervention can be associated with more favorable outcome. To better define the real benefits of metal-on-metal bearings, we must differentiate the bearing-related problems from fixation related issues and implant positioning related issues.