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O R T H O PA E D I C S T O D AY
MEGASYSTEM-C
a replacement system for large
bone deficiencies
®
Compensation of major bone loss after
tumor surgery or repeated revisions requires
implants that can be adapted individually to the
patient and still provide satisfactory function.
The modular LINK® MEGASYSTEM-C® was conceived with such situations in mind. It is based on
tried and tested prosthetic implant systems and can
be combined with existing prosthetic components in the
knee or hip.
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On the subject
About MEGASYSTEM-C®
The reconstruction of bone
structures that have been
destroyed, whether after extensive
tumor resection, repeated
loosening of prosthetic joints,
or after complicated traumatic
injury, is a challenge. Frequently,
large bone and soft tissue
defects have to be functionally
replaced. MEGASYSTEM-C®
offers Orthopaedic Specialists a
highly modular system that allows
individual solutions for the femur.
This implant system was developed
by LINK in collaboration with
Professor R. Capanna of
the Centro Traumatologico
Ortopedico in Florence,
Italy. Based on the tried and
tested Endo-Model® knee joint
prosthesis system and on the
MP® reconstruction prosthesis for
proximal femoral revision, this
makes the system compatible
with existing knee and hip joint
revision prostheses.
Case History
and cementless components
are available. In addition, the
surgeon can vary the length of the
system intraoperatively. The pushthrough stems, provided in various
diameters and lengths, make it
possible to replace the entire femur.
Anamnesis
A system for all occasions
Another advantage of
MEGASYSTEM-C® is that it can
be combined with preexisting
implant components. This
underlines the fundamental idea
in the development of the system,
which is to be able to solve the
problems in variety of clinical
situations using standardized
techniques. This also makes
the modular system attractive
from a cost point of view: only
one instrument set is needed, and
expensive custom-made parts are
not required.
Flexible combination
Replacements are available for
the proximal tibia, the distal
femur, and isolated diaphyseal
or proximal femoral defects;
even total replacement of
the femur is possible. The
individual components
can be flexibly combined
with each other. For the
knee component, for
instance, either the rotation
or the hinge connection
component can be chosen
without the need to remove
the tibial stem or the joint
components. Both cemented
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Push-through
Dr. med.
habil. Jens Decking,
Orthopädische Universitätsklinik
Mainz, Germany
MEGASYSTEM-C®
from top to bottom:
E Sturdy Neck Segment
E Coupling Component
E Stem Segments in E
various sizes
(on push-through stem, not visible here)
Femoral and Tibial Components (cemented or cementless) = paired joints
A 62-year-old woman underwent
total replacement of the right
knee because of gonarthritis.
Aseptic loosening, and later septic
loosening (with proven presence of
MRSA among other things), led to
several revisions and four total knee
arthroplasties exchanges. 3.5 years
later a LINK® Endo-Model®
rotational prosthesis with fully
cemented tibial and femoral
stems was implanted. The patient
suffered no further complications
for four years. Then, at the age of
71, she fell and suffered a spiral
fracture of the femur directly
proximal to the cemented stem
of the rotational prosthesis. The
femoral fracture was managed
externally with a 14-hole LCDC
plate and cerclage. During the
period of building weight bearing,
the patient presented to us again
with severe pain in her right upper
thigh.
Findings
The patient, 110 kg in bodyweight
and 170 cm in height, appeared
in a wheelchair; severe pain in her
right upper thigh made weight
bearing on that leg impossible.
The right thigh showed a swelling
that was painful to pressure.
X-ray showed refracture of the
femur immediately proximal to
the cemented stem of the knee
prosthetic implant with distal femoral replacement in a case of periprosthetic femoral fracture after repeated
exchange total knee arthroplasty
prosthesis. The osteosynthesis
plate had loosened distally, the
fracture had dislocated, and all of
the screws distal to the fracture line
had torn out or broken (Fig. 1).
Treatment
Simply removing the femoral
component from the distal femur
was pointless: at best, thin bone
lamellae without meaningful
stability would remain. The tibial
component, on the other hand,
had not loosened, but was fixed
as strongly as ever. For this reason,
in a first procedure (March 2006)
the distal femur including the
cemented femoral component
(20 cm from the joint line) was
resected and the osteosynthesis
plate, screws, and other metal
parts were removed. The tibial
component was left in place.
Because of the history of several
exchange arthroplasties for sepsis
including evidence of MRSA, a
20-cm Palacos spacer was inserted
into the distal femur (Fig. 2).
Intraoperative culture swabs and
sample biopsy were negative. In a
second operation (April 2006) the
femur was replaced using the LINK®
MEGASYSTEM-C®, employing the
hip replacement variant with a
push-through stem through the
proximal femur and distal condylar
prosthetic component, which
connected with the existing tibial
component (Fig. 3).
On the subject
Replacement of just the distal femur,
retaining the patient’s own hip
joint, would also have been possible
with this modular system. However,
because of the patient’s obesity
and inability to reduce the load on
the joint, and because the proximal
femur was weakened by screwholes
remaining after the osteosynthesis,
this alternative would quickly have
resulted in another fracture.
For this reason the following
procedure was adopted. Through
a mediopatellar approach, E
Fig. 1:
Refracture of the femur after plate osteosynthesis with a cemented Endo-Model®
rotational prosthesis in the right knee. The
dislocated spiral fracture begins at the end
of the femoral cement; all the screws distal
to the fracture have torn out or broken.
The tibial component has not loosened.
In brief
Female patient, born 1935, grossly
obese, diabetes mellitus type IIb,
myocardial infarction 1999, left
total knee replacement 2002
⇒E Right total knee replacement
1997 due to gonarthrosis
⇒E Right exchange total knee
arthroplasties 1998, 2000,
2002 (in part due to MRSA)
⇒E Periprosthetic fracture of right
femur with the prosthesis in
place 2005
⇒E Refracture of right femur with
LCDC plate and prosthesis in
place 2006
⇒E Push-through prosthetic
implant/partial replacement
of the right femur using
MEGASYSTEM-C® 2006
Fig. 2:
The distal part of the
femur was removed
from 20 cm below the
joint line, together
with the femoral
component, and
– because of the
history of sepsis – a
20-cm Palacos spacer
with integrated
metal rod was
inserted. The stable
tibial component of
the Endo-Model®
rotational prosthesis
was left in place.
The proximal femur
is weakened by the
multiple holes left
behind after the
osteosynthesis screws.
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Case History
E a condylar prosthesis with
modular stem segments (in this
case 20 cm in length overall),
with the push-through stem
(14 × 200 mm) attached, was
introduced into the femur from
the caudal end. Next, via an
anterolateral approach to the hip
joint, the roof of the joint was
resected, a spherical cementless
acetabular component was
implanted and finally, the
65-mm-long MEGASYSTEM-C®
neck component was introduced
into the proximal femur from the
cranial end. The neck component
was connected to the push-through
stem with a locking screw, care
being taken to preserve anatomical
rotation. A prosthetic head of the
right size (12/14 mm taper) was
attached. The MEGASYSTEM-C®
condylar prosthesis was connected
to the existing tibial component
by the usual tapping mechanism
(Fig. 4).
Fig. 3:
The MEGASYSTEM-C®
modules assembled
immediately before
implantation. The modules
used were: neck segment
(65 mm long, CCD angle
126°, 12/14 mm taper),
push-through stem
(14 × 200 mm) with support
ring, two stem segments
respectively 30 and 100 mm
in length, and the condylar
prosthesis, which connects
to the tibial component.
Fig. 4:
Postoperative image of the whole leg. Hip joint
replacement with a spherical press-fit acetabular
component and neck segment. The push-through
stem runs through the proximal femur in order to
preserve the trochanter region and the proximally
attached musculature; the distal part of the femur
has been replaced with modular stem segments and
a condylar prosthesis.
Postoperative course
Conclusion
The patient rested the leg
completely (no weight bearing) for
6 weeks, with hip flexion restricted
to 90°. Four months after surgery,
the patient, now aged 72, was
mobile with underarm crutches
and full weight bearing on the leg.
Flexion/extension was 90°/0°/20° at
the hip and 90°/0°/0° at the knee.
In the present case, because
the LINK® MEGASYSTEM-C® is
compatible with the components of
the LINK® Endo-Model® rotational
prosthesis, we were able to leave
the existing stable tibial component
in situ instead of being forced to
exchange it. Owing to the modular
design, it was also easy to correct
WALDEMAR LINK GmbH & Co. KG
Barkhausenweg 10 • D-22339 Hamburg
P.O. Box 63 05 52 • D-22315 Hamburg
Phone +49 (0) 40/5 39 95-0
Fax +49 (0) 40/5 38 69 29
e-mail info@linkhh.de
Internet www.linkhh.de
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the leg length intraoperatively.
Using the variant with the pushthrough stem for the proximal
femur, we were able to preserve
the patient’s proximal femur
together with all its muscular and
tendinous attachments. Given the
patient’s limited ability to avoid
weight bearing, the primary load
stability of the chosen variant was
a further advantage.
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