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Delta
Cup :
The Delta system was designed in 1999 in cooperation with Prof.
Giacometti Ceroni (Galeazzi Institute - Milan, Italy).
The objective of this system is that of enhancing the hip joint
stability by reducing the risk of dislocation in hip
arthroprosthesis, and the tribology performance of articulating
components.
On the basis of Charnley’s experience, the use of small diameter
artificial articulations for metal polyethylene, ceramic-polyethylene
couplings, can be correlated to the reduction in torque transmitted
by friction between the femoral and the acetabular component and
hence also by the reduced volumetric wear.
The long term use of small femoral head has brought at the evidence
another factor as well able to induce deteriorating phenomena for
the polyethylene liners.
The more the spherical area decreases the more the contact stress is
less distributed, that accentuating the penetrating effect in case
of couplings requiring the use of polyethylene.
The diameter of the articulation plays also important leading role
in defining the range of the joint motion.
A large diameter coupling, for example 36mm, offers considerable
advantages in terms of safety.
The use of this type of geometry in ceramic-ceramic couplings
involves torques weighing on the acetabular perimeter that are
inferior or equal to those exerted by 28 mm couplings, thus assuring
a higher articular junction stability with a lower dislocation risk,
since:
• in large diameters the increase in the articular range of motion
reduces the danger of contact between the femoral neck and the
acetabular rim.
• the increase of the typical coupling radius increases the distance
the femoral neck would need to cover in order to come out of the
acetabular seat.
The Delta system was devised keeping these objective facts in mind.
The system also includes the two most common fixation concepts (press-fit
and screw), that have been revised and improved to offer suitable
surgery performance (a better control of the implant position, an
easy insertion of articular liner, a better initial stability,
ergonomic instrumentation) as well as clinical performance (bone
saving, integration).
The Delta system also offers the most advanced
orthopaedic technology in terms of design, with a new liner/metal
back cone coupling section, and of materials, with the
implementation of the innovative Biolox® Delta ceramic as well as of
a new cross-linked polyethylene for which Lima-Lto has studied and
approved a specific manufacturing process.
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