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the tibia to the femoral tunnel. The femoral
fixation is then achieved with bioabsorbable
interference screw (SBM SA, Lourdes,
France).
The knee is then cycled to achieve graft
tensioning. Finally, the tibial fixation is per
formed using a bioabsorbable interference
screw with the knee flexed at 10°-20° and
applying a posterior drawer in order to correct
the anterior tibial translation. Lastly, it is
mandatory to evaluate the graft tension, knee
stability, full range of motion and the eventual
graft impingement.
DISCUSSION
The femoral tunnel can be performed through
different techniques including TT, IO, and OI.
However, in the TT procedure the anatomical
placement of the femoral tunnel is challenging
because of the tibial constraint [2, 9]. As result,
the interest of IO and OI techniques is
increasing because of the possibility to create
an independent femoral tunnel. Nevertheless,
IO technique has some disadvantages, such as
a short femoral tunnel, a possible posterior wall
breakage and a poor visual field [10, 11].
ADVANTAGES
Better footprint coverage
The principal advantages of OI technique are
the more predictable anatomic placement and
footprint coverage, achieving better antero-
posterior and rotatory stability [2].
In a cadaveric study comparing the three
different techniques (TT, IO, and OI), Robert
& al.
[12] show that the average distance from
the tunnel center to the native femoral footprint
center is 6,8±2,68mm for the TT, 2,84±1,26mm
for the IO, and 2,56±1,39mm for the OI
techniques. The average percentages of the
femoral tunnel within the ACL footprint are
32%, 76%, and 78% for the TT, IO, and OI
techniques, respectively. In addition to the
femoral position, the surgeon has to consider
also the orientation of the tunnel drilling to
improve the coverage of the femoral ACL
stump. Matsubara
& al.
[13], in a 3D CT study,
evaluate the optimal position for the OI femoral
tunnel position in order to achieve a better
coverage of the ACL stump. They report that
the mean percentages of the femoral footprint
covered are significantly higher with an
inclination of 45° in the proximal-distal plane.
This orientation provides an oval shape tunnel
that covers and restores the native ACL stump
as nearly as possible.
No risk in posterior tunnel breakage
OI technique is a safer procedure because the
posterior wall preservation is better ensured
and there is no risk of medial condyle cartilage
damaging during femoral tunnel drilling com
pared to IO technique [2] (fig. 5). The intact
posterior wall allows femoral press-fit fixation
in case of BPTB graft. Posterior wall breakage
is one of the disadvantages of IO procedure,
reporting an incidence of 23,8-33% [14].
Remnant preservation
To our knowledge, in literature there are no
studies that compare the remnant preservation
using the three different techniques. However,
it is advantageous to conserve the remnant
because it improves the graft vascularization,
the ligamentization and the proprioception of
the knee [15].
Revision surgery
OI technique can be used easily in revision
surgery where it may be necessary to drill a
femoral tunnel with a different orientation
avoiding previously enlarged and misplaced
tunnels [8].