الفهرس 
Functional anatomy of the hip jointOnly 14 pages are availabe for public view
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Abstract
Summary
The hip joint is multi-axial, synovial, and of ball and socket variety . The hip joint provides a remarkable example of a high degree of stability and range of motion.
Its stability is largely the result of the adaptation of the articulating surfaces of acetabulum and femoral head to each other and its great range of mobility results from the femur having a neck that is much narrower than the equatorial diameter of the head.
Instability remains a significant issue after both primary and revision THA. Dual mobility or tripolar unconstrained acetabular components can provide a viable alternative in preventing and treating instability. Hence there is increasing interest in dual-mobility bearings as an alternative to standard articulations, as they are associated with a low risk of instability following primary and revision THA. Additionally, they may serve as an alternative to traditional solutions for instability including large-diameter heads and constrained liners.
Reported outcomes of studies using DM cups with mid- to long term follow up support their effectiveness. DM cups are recommended to reduce the frequency of dislocation, particularly in patients at high risk. The two primary concerns with dual mobility cups remain wear and IPD. However , recent studies reported decreased incidence with newer generations and they seem to be less significant in older, low-demand patients.
Dual Mobility cups should not be used in active patients younger than 50 years, owing to the long term risk of osteolysis, loosening, and intraprosthetic dislocation. In contrast, DM cups may be advocated in patients younger than 50 years with neuromuscular impairment (Parkinson’s disease, dementia, palsy), who are at high risk of dislocation but usually have a low activity level and low risk of osteolysis.