الفهرس 
Biomechanics oF the total hip ProsthesesOnly 14 pages are availabe for public view
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Abstract
The dual-mobility concept in THA was developed in the 1970s by Gilles Bousquet and Andre´ Rambert from France. The idea was to combine the ‘‘low-friction arthroplasty’’ principle of charnley together with the advantage of a big femoral head principle of MacKee. The initial design of the cup had tripod fixation points on the rim of the shell along with an alumina ceramic outer coating. The newer-generation sockets have a dual-layer hydroxyapatite and alumina ceramic coating to enhance bony in-growth.
The shell is hemispherical with 0.5-mm polar effacement for better seating in the native acetabulum. The polyethylene insert is modified with a chamfer margin to reduce impingement on the neck of the femur prosthesis.
The Serf Novae_ Dual Mobility Acetabular cup has the advantage of increased range of movement (up to 186_), better coaptation between the components and less stress on the bone implant interface, and is available in a range of sizes (43–69 mm for un-cemented, 43–63 mm for cemented fixation) and has options for cemented, cementless or reconstructive surgery. It can be used with either a 22.25- mm or a 28-mm femoral head.
One of the potential disadvantages levelled against dual mobility articulation is the theoretical increased risk of polyethylene wear, because both the concave and convex surfaces of the polyethylene liner articulate with the metal components. However, a retrieval analysis study of 40 dual-mobility sockets showed that both the mean total wear of the polyethylene liner was not more than that for conventional metal–polyethylene bearings.
A unique complication of the dual-mobility socket is intra-prosthetic dislocation (IPD). In this scenario, the femoral head dislodges from the mobile polyethylene liner. The metal head can then articulate with the metal socket, leading to devastating complications, including severe metallosis*.
The indication for using a dual-mobility socket is like hip trauma, primary hip arthroplasty and revision THA..
Studies have shown that meticulous surgical technique with careful soft tissue repair is essential to avoid instability, irrespective of the approach used.
Even though prosthetic hip stability depends on many factors other than the implant-related ones, the good results shown in this study reinforce the excellent outcomes reported in the literature, in both primary and revision THA, for the efficacy of dual-mobility cups in managing hip dislocation.