94 / 244
ANTEVERSION AND LENGTH OF THE FEMORAL TUNNEL IN ACL RECONSTRUCTION…
93
DISCUSSION
The lesions described when drilling the femoral
tunnel, via the antero-medial portal, using rigid
instrumentation are
1)
lesions of the posterior/
external structures when passing the guide pin
[1-3] and
2)
perforation of the posterior bone/
cartilage [1, 2] during the drilling.
On cadaveric knees, using the rigid
instrumentation, Basdekis
et al.
[5]
systematically reported contact between the
guide pin and the posterior cortex with a 90°
flexion and, Steiner
et al.
[6], reported a 50%
perforation of the posterior cortex at 110° of
flexion. Clinically, this violation of the
posterior femoral cortex could compromise
graft fixation and healing.
Hall
et al.
[3] assessed the relationship between
knee flexion and the risk of the common
peroneal nerve injury. The mean distance from
the guide pin at 120° of flexion was 44.3mm,
compared with 28.6mm at 90° of flexion and
22.8mm at 70° of flexion. The differences
between all 3 groups were statistically
significant.
The other risk mentioned when using the
antero-medial portal was producing too short a
femoral tunnel [1, 4], which could potentially
compromise the fixation and osseointegration
of the transplant. A minimum femoral tunnel
length for ACL reconstruction has not been
established, but a minimum length of 25mm
for interference screw fixation and a minimum
length of 35mm for suspensory-type fixation
have been suggested [7, 9].
However, in the antero-medial portal technique,
with rigid pins, the length of the femoral tunnel
is often inadequate, particularly when the knee
is not in hyperflexion. Basdekis
et al.
[5]
compared the length of the femoral tunnel
according to the knee flexion; at a flexion of
90°, the length of the tunnel was 27mm; while
at 110°, 130° and at maximum flexion, the
mean length was approximately 39mm.
Fig. 5:
Pos-op X-Ray with rigid instruments
Fig. 6 :
X-Ray with flexible instruments