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NexGen MIS LPS-Flex Mobile Implant System
Surgical Technique
MIS LPS-Flex Mobile Tibial Implant
The MIS tibial component is the first tibial implant
designed to simplify the insertion of the tibial plate
through a minimally invasive incision. The stem/fin
geometry fits within the minimal 20 mm gap created
after bone resection. The stem lengths are 17 mm or
19 mm, depending on implant dimension. The MIS
LPS-Flex mobile tibial component incorporates the
same bottom geometry (Figure 3).
Broad fins are located in the proximal tibial region
with the highest bone density providing resistance to
bending moments.
1
This fin position was established
based on the experience with the post position in the
Trabecular Metal™ monoblock tibial plates.
NexGen MIS LPS-Flex
Mobile Bearing Knee
The NexGen
®
MIS LPS-Flex Mobile Bearing Knee
is a posterior stabilized prosthesis designed to
accommodate greater range of motion for appropriate
patients, such as those who are physically capable or
whose cultural customs or recreational/work activities
require deep flexion.
The development of the LPS-Flex mobile bearing knee
is the result of an analysis of a knee prosthesis as it
undergoes deep flexion beyond 120 degrees. For
example, the interaction of the posterior condyles on
the articular surface was carefully studied. As a result,
efforts have been made to optimize the contact area as
the posterior condyles roll back to flexion angles up to
155 degrees (Figure 1). This is addressed by thickening
the posterior condyles, thereby extending the radius.
The tibial articular surface was also considered in
the design. In deep flexion, the extensor mechanism
experiences a high level of stress as the soft tissues are
stretched and pulled tightly against the anterior tibia
and distal femur. The LPS-Flex mobile bearing knee
is designed to help relieve these stresses through a
larger, deeper anterior cutout on the articular surface
(Figure 2). This cutout accommodates the extensor
mechanism in deep flexion.
Additionally, the cam/spine mechanism has been
modified to provide greater jump height as the knee
prosthesis undergoes deep flexion between 120
degrees and 155 degrees. The cam/spine mechanism
induces mechanical rollback while inhibiting posterior
subluxation of the tibia.
These design features accommodate high-flexion
activities and, together with proper patient selection,
surgical technique, and rehabilitation, increase the
potential for greater range of motion. The LPS-Flex
mobile bearing knee components can be implanted
using any of the NexGen Knee Instrument Systems.
Figure 1 – Contact area at 155°
Figure 2
Figure 3
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