Stem Migration and Fretting Corrosion of the Antirotation Pin in the K2/Apex Hip System

Michael Kent, Mark Edmondson, Jay Ebert, Nils Nivbrant, Alan Kop, David Wood, Richard De Steiger

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
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Background: Many exchangeable neck hip systems have been withdrawn because of fretting corrosion at the neck/stem coupling. Method: Our prospective randomized study evaluating stem stability (Roentgen stereophotogrammetric analysis, dual-energy x-ray absorptiometry) and clinical outcomes between the K2/Apex hip systems was ceased early because of a withdrawal of the stems which had an unfavorably high early revision rate reported in the Australian Orthopaedic Association National Joint Registry (9.3% at 3 years). Results: At 2 years, there are no clinical differences between the stems. Roentgen stereophotogrammetric analysis has identified a high proportion of potentially concerning subsidence and retroversion in both groups, more marked in the K2 stem, although mostly in asymptomatic patients. Dual-energy x-ray absorptiometry has shown similar bone density around the stems. Retrieval analysis of 3 study patients showed fretting corrosion of the antirotation pin and aseptic lymphocyte-dominated vasculitis-associated lesion, with no relationship to bearing type or size. Analysis of 7 further nonstudy K2/Apex stems confirmed similar corrosion. Conclusion: This study shows potentially concerning subsidence of both stems and is the first to describe corrosion at the neck-stem interface and a relationship to metal-related pathology.

Original languageEnglish
Pages (from-to)727-734
Number of pages8
JournalJournal of Arthroplasty
Issue number3
Publication statusPublished - 1 Mar 2016


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