Based on our experience with an anatomically shaped-femoral stem - helitorsion stem - and on the concept of rotatory locking, we presents our results in osteointegration and bone remodeling.

The study is documented in a prospective study of 84 consecutive helitorsion implants with 6 years 8 month follow-up with no exclusion critera relative to age, gendre, morphology of the femur, bone density, etiology. The stem: forged titanium alloy; roughness 6.5 achieved with corundum treatment; conical proximally, cylindrical distally; double curvature in the sagittal plane; in the horizontal plane, replicates the natural helix of the femurits main feature-; HA coating(200μm) over its proximal 2/3. Stem insertion: helicoidal motion along the long axis of the femur and rotation in the horizontal plane. Rotation is mandatory. The stem is pushed down until the oval shape of the stem matches the oval shape of the femur – at each metaphyseal level – over a more or less extended height depending on the femoral morpho-type; this horizontal locking prevents further downard motion.

This uncemenred helitorsion stem yelds remarkably good radiological results: there is a radiological silence. We think that is attribuable to helitorsion with ensures an even distribution of loads, and applies oblique and not perpendicular loads to the bone-implant interface

Our experience with metal/metal desings in France date from 1994. The goal of this study is to communicate our primary and comparative clinical results of 90 implants followed a minimum of 6 years

Material and method: We have reviewed the first 94 patients from our first year using metal/metal.90 case files were complete and we compare thes patients (group 1) to a control group of 90 patients receiving ceramic/poly couple, operated in the same time period (group two) with the same hybrid TH system. Average follow up: Five years and eight months.

Results and discussion: 4 of the 94 were unavailable for follow up at six years. None of these patients experienced clinical problems relared to the metal/metal. The clinical results (Merle and Harris score) are all good or excellent and there is no difference between the 2 groups. The x-ray results: For acetabular cup the two groups are identical and for femoral component (Barrack evaluation) all two groups have the same quality of cementation and maintain the cement mantle integrity achieved post-op. We decided therefore to examine specially the RLL changes in zone seven (comparison 3 month x-ray/latest follow-up x-ray); significant differences between the two groups were found in this study: The lower incidence of zone seven radiolucent changes in group one indicates a better clinical tolerance in the metal/metal configuration (p=0.0256). Considering the results reported here and the advanced studies, we can confirm that metal/metal systems are not the unique answer to PE-wear and THA longevity, but it is one solution that is available today and seems trustable.