Historical aspects, a comparison of models and a review of the literature
A.E. Salvi*, G. Grappiolo**, G. Moraca**, L. Spotorno**
*Azienda Ospedaliera “Mellino Mellini”, Presidio Ospedaliero di Iseo (Brescia), Divisione di Ortopedia e di Traumatologia
**Azienda Ospedaliera Ospedale “Santa Corona” di Pietra Ligure (Savona), Divisione di Chirurgia Protesica del Reumatismo Articolare, Fondazione “Scienza e Vita”
Cappelli editore, Bologna 2005 Chir. Organi Mov., XC, 323-337, 2005
The article describes the features of the most commonly-used acetabular components in first implants in light of development in construction as regards intrinsic features, materials used, biological behavior, and design. The following versions are examined: screwable cone-shaped trunk, cemented polyethylene, cemented metal- back, HA-coated press-fit, expansion, dysplastic hip, and anti-dislocating components. The screwable cone-shaped trunk acetabular component takes hold in the acetabular bone through torsion and compression, and threading provides greater stability as compared to equivalent models that have wings or screws. Cemented polyethylene acetabular components are characterized by low costs and good results, on the condition that some specific parameters are respected (the presence of a dry bone bed, pressurization of the cement, use in elderly patients who do very little physical activity). Cemented metal-back acetabular components have features similar to polyethylene components, from which they differ because of the possibility of being able to substitute the internal polyethylene component without having to revision the entire acetabulum. HA-coated press-fit components have solved the problems encountered in cemented versions, such as loosening and the generation of polyethylene particulate, at the same time obtaining excellent osteointegration. The expansion cup self-stabilizes thanks to a memory effect due to the contraction-relaxation mechanism with which it is lodged, adapting to the micromovements of the acetabulum. Components used in the dysplastic hip are particular versions with a reduced diameter that have specific hooks that provide stabilization, capable of settling in the pathologic bone with minimum reaming of the same. Anti-dislocation cups are special models that have bipolar inserts or a ring (plastic or metal) that blocks the head in the prosthetic acetabulum, obstructing its dislocation.
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