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IS THE ANATOMIC FEMORAL TUNNEL MANDATORY?
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notch, change during passive range of motion.
With respect to the tibial plateau AM bundle is
more vertical in the first 80 degrees of flexion,
whereas PL bundle is more vertical between
80° and 120°. Considering angle between ACL
and femoral notch, it increases progressively
with flexion, and at 120° of flexion AM and PL
have the same orientation, whereas there is a
difference in orientation of 10° at full
extension. Comparing AM and PL bundles
behaviour during flexion, a major increase of
the angle of PL with femoral notch during
flexion could be noted.
These findings suggest that ACL forms a very
complex system and the goodness of its
reconstruction cannot be depend only on the
reproduction of the exact insertion location, but
also the orientation of the graft should be
considered. ACL creates an isotropic system,
difficult to reproduce inACL reconstruction; so
the best compromise to restore normal
biomechanics and normal kinematics after
ACL injury is an isometric reconstruction.
The isometric placement of the graft avoids
changes in graft length and tension during knee
flexion and extension to avoid graft failure by
overstretching. Several studies have shown
that positioning the femoral tunnel position
inside the anatomical footprint results in knee
kinematics closer to a normal knee than
isometric tunnel [7]. To capture the entire
footprint, a double boundle reconstruction is
desirable, but the greater technical expertise
and potential for complication make it non-
universally accepted. So surgeon that decide to
perform an anatomical femoral tunnel should
select a portion of the native femoral attachment
where prepare the tunnel. The rationale for an
anatomic AM reconstruction is that the AM
bundle is large and more isometric [8].
However Cross
et al.
[9], comparing antero-
medial versus central single bundle position,
has demonstrated that two compared
anatomical technique were equally effective in
controlling anterior tibial translation during a
Lachman examination, but neither is able to
restore native knee kinematics, as indicated by
decreased control of anterior translation of the
lateral compartment during pivot shift.
Over the top technique associated to lateral
plasty, described by Marcacci
et al.
[10], allows
good results associating an intra-articular
reconstruction and an extra-articular re
construction in order to reproduce the antero-
lateral ligament and its function. Positioning
graft in over the top position reproduce the
anatomical insertion of the major functional
part of the ACL. It’s showed that creating a
groove in the lateral femoral condyle at the
junction with the roof (11 or 1 o’clock position)
led to a modified over-the-top position with
approximation to an isometric placement.
Long-term follow up has demonstrated good
results in terms of rate of failure and rate of
osteoarthritis [11].
Moreover it was demonstrated that over the top
associated to lateral plasty provides to restore a
good stability and kinematics of the knee: it
reduces anterior displacement of the lateral
compartment of the tibia and controls internal
and external rotation at 90° of flexion [12]. It’s
less effectiveness in controlling dynamic laxity
than anatomic double bundle procedure, but
it’s easier and more reliable. Moreover it’s less
aggressive to the joint, as it doesn’t require a
femoral tunnel and it doesn’t violate any lateral
structure.
Furthermore McCarthy
et al.
[13] demonstrated
good results of over the top technique in
pediatric reconstruction, similar to all
epyphiseal reconstruction.
CONCLUSION
Among several technique proposed for ACL
reconstruction, “over the top” technique shows
many advantages that make it the ideal surgery.
“Over the top” technique allows an isometric
placement, respecting anatomical origin of
ACL; not using femoral tunnel, it avoids
malposition of the femoral tunnel and,