Wednesday, December 14, 2011

Accelerating failure rate of the ASR total hip replacement: 6 year post surgical rate of 48.8%

J Bone Joint Surg Br. 2011 Aug;93(8):1011-6.

 

Source

Northern Deanery, Goldcrest Way, Newcastle upon Tyne NE15 8NY, UK. djlangton22@doctors.org.uk

Abstract

There is widespread concern regarding the incidence of adverse soft-tissue reactions after metal-on-metal (MoM) hip replacement. Recent National Joint Registry data have shown clear differences in the rates of failure of different designs of hip resurfacing. Our aim was to update the failure rates related to metal debris for the Articular Surface Replacement (ASR). A total of 505 of these were implanted. Kaplan-Meier analysis showed a failure rate of 25% at six years for the ASR resurfacing and of 48.8% for the ASR total hip replacement (THR). Of 257 patients with a minimum follow-up of two years, 67 (26.1%) had a serum cobalt concentration which was greater than 7 μg/l. Co-ordinate measuring machine analysis of revised components showed that all patients suffering adverse tissue reactions in the resurfacing group had abnormal wear of the bearing surfaces. Six THR patients had relatively low rates of articular wear, but were found to have considerable damage at the trunion-taper interface. Our results suggest that wear at the modular junction is an important factor in the development of adverse tissue reactions after implantation of a large-diameter MoM THR

 xxxxx (information below is not a part of the article above but is taken from the Langton, Joyce slides which I published a week ago.

I wanted to reprint From the Langton slides the bands of progressive problem metal levels as it is the best one I have found and I get this question continuously....

If the ion levels are elevated above 7ppb for either Cr or Co (parts per billion or 7 micrograms/liter) second set of tests should be performed.

Cobalt ladder

1ppb
physiologic

2ppb
upper normal limit for patients with hip resurfacing

5ppb
abnormal ware

10 ppb
60% show ARMD (adverse reaction to metal debris) within 3 years

20ppb
metalosis

(remember ppb and micrograms per liter are the same.)


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