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INTRODUCTION
The anterior cruciate ligament (ACL) is divided
into two bundles, based on their insertion in the
tibial footprint, the anteromedial (AM) and the
posterolateral (PL). They are parallel in
extension, but change into being crossed in
flexion. AM bundle is tight in knee flexion,
conversely PL is tight in knee extension.
The native ACL femoral footprint occupies a
very large area, extended about 115-230mm
2
[1] and it was demonstrated that a 9 mm graft
would cover about 33% of the footprint cross-
sectional area and 50% of the isometric profile
of the native ACL profile [2].
Because of that it’s very difficult to duplicate
the large anatomic footprint and surgical
techniques that try to reproduce anatomical
insertion represent a challenge as well for more
experienced surgeons. Isometric point is
located in a small area of the ACL insertion, the
over-the-top position, sited high in the femoral
notch. Isometric placement of the graft is easier
to reproduce and allows avoiding change in
graft length and tension during flexion and
extension of the knee.
DISCUSSION
In order to understand how to restore the better
stability and kinematics in ACL reconstruction,
several studies have investigated about
anatomy and biomechanics of the femoral
insertion of the ACL.
An anatomical study [3] has demonstrated that
femoral insertion area of ACL is a large oval
area, whose mean length of the long axis is
17.7 ± 2.7mm; it could be divided into a direct
insertion with a four-layered structure and a
two-layered indirect insertion, where Sharpey
like fibers were found.
The direct insertion plays a more important role
in the mechanical link between ligament and
bone than indirect insertion. Instead indirect
insertion is a dynamic anchorage of soft tissue
to bone, allowing shear movements, but it has a
weaker strength than direct insertion [4].
Kawaguchi
et al.
[5] has demonstrated that a
sequential cutting of the different areas of the
femoral ACL attachment produces a
progressive reduction of the force required to
realize a 6mm anterior displacement at any
IS THE ANATOMIC FEMORAL
TUNNEL MANDATORY?
S. ZAFFAGNINI, G. CARBONE, A. GRASSI, F. RAGGI,
T. ROBERTI DI SARSINA, C. SIGNORELLI