Abstract
Concerns with long-term fixation of cemented all-poly sockets have led to the near-universal acceptance of cementless fixation of the acetabulum.
The sockets most often utilised today are bone-ingrowth porous metal, made of titanium, cobalt-chrome, or hyper-porous materials such as tantalum trabecular metal.
Porous ingrowth sockets are extraordinarily reliable, with reports of 99–100% achieving stable fixation. The problem with sockets is not the fixation, but the bearing. Modular polyethylene liners are most commonly used, but wear on the primary bearing surface as well as backside wear can lead to osteolysis and late failure. Holes in the socket designed for supplemental screws act as a conduit for particles to enter the ace tabular bone where a cascade of inflammatory responses activate osteoclastic activity and bone destruction.
One alternative is a socket without holes, using spikes or fins for additional stability. The concern here is that the socket may not be completely seated and the surgeon is unaware.
Another alternative is the use of a monoblock acetabular component with the polyethylene molded to the metal shell. While excellent results are reported, the downside is an inability to exchange the polyethylene.
Resurfacing sockets are also monoblocks, and some offer peripheral supplemental screws. Here again, incomplete seating may occur, leaving a gap behind the dome. Serial x-rays almost always reveal that this gap gradually fills in.
Improvements in polyethylene, better locking mechanisms and alternative bearing materials such as ceramic and metal are the final steps to ensure acetabular durability.
