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F. WEIN
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To avoid perforating the posterior cortex,
damaging the nerves and drilling a femoral
tunnel that is too short, it is recommended that
the knee should be flexed at 110° or more [3,
5]. However, as Lubowitz [1] points out,
positioning the knee in hyperflexion during
ligament reconstruction raises operative
challenges:
“inability to maintain the position
of a properly seated aimer when the knee is
brought into the requisite, hyperflexion
position; difficulty bringing the acorn reamer
over the Beath pin and through the AM portal
with the knee in hyperflexion, because
hyperflexion causes the portal to tighten;
difficulty avoiding iatrogenic damage to the
cartilage of the medial femoral condyle as the
acorn reamer is advanced over the Beath pin in
the hyperflexed knee; difficulty passing the
reamer over the Beath pin because of a bend in
the pin when the knee slips out of hyperflexion;
difficulty visualizing the reamer because of
ingress of the fat pad, which also occurs when
the acorn reamer is advanced over the pin in
hyperflexion; difficulty maintaining the position
of the arthroscope (generally held by an
assistant) in the hyperflexion position; difficulty
visualizing the depth markings on the acorn
reamer despite proper arthroscope positioning
during socket creation, because of the
combination of reaming debris and poor flow
of arthroscopic fluid, which occurs in
hyperflexion.”
It is precisely to overcome these surgical
difficulties that it is worthwhile using
instrumentation with a flexible system, first
introduced by Cain and Clancy [8], as the
positioning of the pin is achieved, not through
changing the angle of the knee, but through the
positioning of the aimer. The joint is easier to
visualise [4] and the femoral tunnel easier to
position [6].
The purpose of our study was to confirm the
ability of the flexible system to drill a femoral
tunnel
via
an antero-medial portal without the
risk of causing posterior bone/cartilage lesions
and common peroneal nerve damage, with the
knee at 90°. To compare the risks involved
when drilling the tunnel, our study measured
the position of the femoral tunnel on post-
operative profile X-rays [10]. As the posterior
structures are most likely to be compromised,
we noted a correlation between the degree of
anteversion and a lowering of the risk of
damage to these structures.
In our work, the anteversion obtained using the
flexible system, with a knee flexed at 90°, was
40°; it was only 20° with the rigid system, at a
flexion of 120°. The difference between these
two angularities was significant.
The length of the femoral tunnel drilled with a
flexible system was also on average 41mm, a
length significantly longer than the one
obtained with a rigid system at a flexion of
120° (34mm).
Our study therefore confirmed the option of
using flexible instrumentation via the antero-
medial portal at 90° of flexion, with a longer
femoral tunnel and with fewer risks of posterior
perforation of the lateral condyle and posterior/
external lesions when drilling the femoral
tunnel compared with rigid instrumentation at
a flexion of 120°.
CONCLUSION
With the flexible system, it is possible to drill a
femoral tunnel via an antero-medial portal,
with the knee flexed at 90°. This option makes
it easier to perform ligament reconstructions,
as the intra-articular view and surgical
procedure are easier at 90° compared with
higher flexion angles. With this system, the risk
of posterior bone/cartilage lesions and common
peroneal nerve damage, described when using
the antero-medial portal, is lower. The femoral
tunnel is also long enough to allow the use of
all types of fixation and encourage good
osteointegration.