Causes for revision of dual-mobility and standard primary total hip arthroplasty : Matched case-control study based on a prospective multicenter study of two thousand and forty four implants.

INTRODUCTION: The causes for revision of primary total hip arthroplasty (THA) are various and quite well known. The developing use of dual-mobility THA (DM-THA) seems a relevant option to decrease the risk of instability. Due to lack of long-term follow-up, this innovative retentive concept is suspected to increase the risk of polyethylene (PE) wear. the aim of the study was to analyse the causes for DM-THA revision and assess whether or not its occurrence is different from that of fixed-standard (FS) THA , particularly for aseptic loosening or wear and/or osteolysis.

MATERIALS AND METHODS: The SoFCOT group conducted an observational prospective multicentre study from 1 January 2010 to 31 December 2011. Inclusion criteria comprised an exhaustive collection of 2044 first-revision THAs with 251 DM-THAs and 1793 FS-THAs. After excluding complications linked to patient factors (infection and periprosthetic fractures), we performed a matched case-control study (matching ratio 1:1) comparing two groups of 133 THAs.

RESULTS: Revisions for aseptic loosening or osteolysis/wear were as frequent in DM-THA (58.7 %) as in FS-THA (57.1 %) (p 0.32); 7.5 % of DM-THA were revised for dislocation versus 19.5 % of FS-THA (p 0.007).

DISCUSSION: Revision for osteolysis/wear and aseptic loosening were as frequent in DM-THA as in FS-THA; revision for dislocation was less frequent in DM-THA. This confirms the efficiency of the DM concept regarding the risk of dislocation. Causes for revision were different between groups, and revisions for dislocation were less frequent in DM-THA. Only prospective comparative studies could provide reliable information that may support broader use of the DM concept.