Purpose The longest follow-up dual mobility series from inventor Gilles Bousquet focussing on implant survival and the incidence of dislocation. Methods This was a retrospective study from 1985 to 1990, on 240 hips using a PF® modular femoral stem and a dual mobility Novae® tripodal socket (SERF). Results The 22-year follow-up global survival rate was 74%. No dislocation occurred, 41 hips were revised, including ten retentive failures (RF), 12 hips were lost to follow-up, 87 patients (99 hips) died without revision, and 90 hips were still in situ. Conclusion The dual mobility socket global survival rate is comparable to similar series. The 0% dislocation rate demonstrates the success of dual mobility with regard to implant stability. The main issues were cup fixation, which might be improved by the use of macrostructures and HA coating, and osteolytic lesions, caused by polyethylene wear. Traditionally suitable for patients older than 60 years, dual mobility might be extended for use in patients over 50.

Publié suite au congrès : 15th International Conference on Wear of Materials, July-August 2005International audienceIn the biomedical field, about 6% of hip total joint prostheses have to be replaced after 9 years because of a loosening of the femoral stem. One of the main causes of a new surgical intervention is attributed to the phenomenon of fretting-corrosion, i.e. wear under small movements (lower than 100 µm) in corrosive aqueous medium. To understand this degradation, the fretting between 316L steel and PMMA has been investigated to simulate the fretting between femoral stem and bone cement. First, fretting in air has been studied as a reference environment. No significant wear was observed on the stainless steel. PMMA suffers a wear that exhibits a linear evolution as a function of the cumulated dissipated energy. Third body evolution could explain the particular W shape of the active wear track in PMMA, in dry conditions. In aerated Ringer's solution, at free corrosion potential, stainless steel suffers significant wear damage, and the wear volume increases linearly with time but not with dissipated energy. Moreover the optical observations and three-dimensional (3-D) profilometry show a 'W' shape of the wear track of 316L. A corrosion mechanism involving a crevice effect enhanced by fretting allows to explain the location of the maximum damage zones. Finally, the effect of electrochemical potential on the behaviour of 316L/PMMA contacts has been studied by recording current intensity and cumulated dissipated energy under potentiodynamic conditions. Dissipated energy exhibited a reproducible variation with potential. Lubrication regimes and effect of potential on the surface charges could account for such a behaviour

International audienceIn hip implants, UHMWPE (ultra high molecular weight polyethylene) liner wear is believed to be a key issue affecting the lifetime of the artificial joint. Dual mobility, a THA (total hip arthroplasty) concept where the liner moves inside the metallic shell, has become popular due to its low dislocation rate. To understand the tribological behavior of this particular implant, especially the role of the second mobility, 12 representative explants were selected from a bank of 250 explants. The implants used were Profil® femoral stem and Novae® metallic shell. The external surface, involved in the second mobility, was examined by 3D profilometry, SEM (scanning electron microscopy) and CMM (coordinate measuring machine). This study highlights a correlation between roughness and CMM evolutions and surgical parameters. A particular wear zone and a wear scenario were identified and validated according to the type of metal-back. A metal transfer between the metal back and the liner was isolated. CMM allowed to measure second mobility wear volume at a macroscopic scale. Thus a realistic wear mechanism has been suggested for this specific implant