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Revizyon :
The Revision stem is the result of the experience
gained with the LCR system: different round section
stem designs, mechanically connectable to a series
of modular necks, fixed by Morse taper and safety
screw.
The LCR (1982) cementless revision prosthesis
demonstrated the efficiency of the modular design in
revision cases.
From the clinical point of view, the use of a
tapered stem with round finned section gave very
good results with the success of Wagner revision
prostheses.
These positive results, widely confirmed by the
literature, as well as the experience gained with
LCR prosthesis, lead to the study of a new femoral
prosthesis for reimplantation called Revision.
The first application of the implant dates back to
1996.
Starting from the experience acquired with Wagner
type prostheses, the Revision stem project was
characterised by the search for an appropriate
modular solution to overcome the surgical and
functional limits typical of the monolithic design.
The surgical technique applied with the Revision
stem is similar to that used with a traditional
Wagner cementless revision prosthesis.
However, the two-time approach and the stem modular
design make it extremely flexible: the primary
fixation objective is separated from the restoration
of the articular function and can be easily obtained
without the risk of precluding or modifying the
final articular anatomical frame, thanks to the
availability of proximal modules of different
heights.
The flexibility of the implant is also supported by
the search for overall reliability.
Particular attention was paid to the design of the
coupling taper.
Different approaches were adopted.
The anatomical aspect was analysed to allow the
implant adaptation to the configuration normally
taken by the femur with respect to the lateromedial
plane, thus making the Revision stem unique in its
gender, though having a straight design.
The structural mechanical behaviour was calculated
and simulated in a virtual environment (finite
element analysis). Severe experimental laboratory
tests were carried out to check the dynamic
performance in the worst load and posture conditions,
to guarantee the reliability of the coupling in
time.
The technological know-how acquired in the
metallurgical field allowed Lima-Lto to develop and
industrialise a specific heat treatment for the
Ti6Al4V titanium alloy which increases the alloy
general mechanical performance and in particular its
resistance to fatigue, increasing it by 20% with
respect to that of the alloy in its starting
conditions.
The mechanical machining of the tapered surfaces is
also critical as it determines the roughness, a
parameter which affects the tribological behaviour.
In the Revision stem, the typical roughness of the
tapers prevents the onset of corrosion due to
mechanical reasons.
The number and the configuration of the components
supplied intraoperatively, with the support of a
simple and efficient instrument set, allow the
operator to easily manage surgical-related limits,
by dividing the femoral operating time into two
segments, one dedicated to the choice of the stem
and the other to the choice of the articular portion,
always having the possibility of checking the best
overall dimensions.
Since 2007 the availabilty of new odd intermediate
sized reamers allows for a precise gauging of the
femoral canal.
The flexibility of the surgical act guides the
operator with safety during the operation phases and
the implant modular design widens the treatable
morphological range, allowing a balanced recovery of
articular motions.
The restoration of a correct biomechanics associated
to optimum primary stability are possible in all the
revision cases presenting considerable loss of bone
stock and alterations of the proximal anatomical
frame
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