POSTER ABSTRACTS - ISAKOS

etween using the dominant or the non-dominant
hand in instrumenting when measured by
evaluating the graft placement using the method
of ''the sum score of the graft placement'' and
duration of surgery. However, there was a
significant difference in the femur positions of the
knees operated by the right-handed surgeon (P =
0.007).
E-poster #331
Computer-Assisted Comparison of Two Doublebundle
Techniques for ACL Reconstruction
Stefano Zaffagnini, Bologna, ITALY, Presenter
Sandra Martelli, Bologna, ITALY
Marco Bontempi, Bologna, ITALY
Simone Bignozzi, Bologna, ITALY
Laboratorio di Biomeccanica, Bologna, ITALY
Introduction:
In this study we present a new method to analyse
the double-bundle ACL reconstruction, based on
the use of a navigation system to track passive
motion and to digitize anatomical data and
successive computer elaboration of the
kinematics. The accuracy of the system allows a
reliable analysis also of secondary kinematic
constraints and, on cadaveric specimen, also a
reliable study of the relationship with anatomical
features [1, 2].
This study describes the acquisition and
elaboration protocol of the methodology and
reports a case study to investigate the effect of
tunnel orientation in double-bundle ACL
reconstruction on the kinematics of the
reconstructed knee.
Materials and Methods:
We performed the comparison of two doublebundle
techniques for ACL reconstruction in two
cadaver knee, using an optical navigation system
(FlashPoint, Image Guided, Boulder, Colorado) to
record relative motion of the tibia and the femur
and to digitize anatomical data. The acquisition
protocol of our study was the following:
1.1 Limb preparation.
Femur was fixed horizontally with tibia, at 90deg
of flexion, perpendicular to floor in order to
minimize external forces, like varus rotation, and
have a physiological passive range of motion.
Two rigid bodies with infra-red emitters were fixed
respectively to femur and tibia in order to record
the relative position during passive motion.
1.2 Tests
The passive range of motion during flexion, the
internal/external rotation at 90deg of flexion, at
maximum force, and the drawer test, at maximum
force, were recorded twice by the same operator in
the ACL intact knee.
Then the ACL was dissected, and the ACLdeficient
knee kinematics was examined
performing again the passive range of motion, the
internal-external rotation at 90? and the drawer
test with the patella in situ, like in the previous
case.
The gracilis and semitendinous tendons were
harvested and sutured together with the tibial
insertion left intact. A tibial tunnel was performed
in a way to reach the natural tibial insertion area
of ACL, in particular its postero-medial part. The
tunnel started in the medial part of cresta tibialis
and had an orientation of 9deg respect to the
anatomical axis in the frontal plane and 30deg
respect to the sagittal plane.
From the femoral insertion two femoral tunnel
with different orientation were performed, one at
40deg with respect to the tibial plateau in flexion,
that we call horizontal, and one at 65deg that we
call vertical. The tendons were passed through the
tibial tunnel, over the top, in the horizontal tunnel
and in the tibial tunnel again. The tendons were
then clamped and cinematic tests were repeated.
Same protocol was followed for the vertical
tunnel.
The final bundle of ACL goes from tibial tunnel to
over the top in order to reproduce the posteromedial
bundle of the reconstructed ACL. The
other bundle of the reconstructed knee went from
the tibial tunnel to the femoral tunnel in both
cases, and was identified as the antero-medial
bundle.
In order to have a complete description of the
joint the knee was then dissected and bone
surfaces, tunnel and ligaments insertions were
digitized.
1.3 Computer analysis
The computer analysis of the knee joint and the
kinematic data was performed with a custom
software that allows the reconstruction of relative
motion of the joint and the computation of
laxities, as well as instantaneous rotations and
translations [1].
During anatomical acquisitions transepicondylar
line and mechanical axis on femur and medial
lateral direction and anatomical axis on tibia were
acquired and used as local reference coordinate
systems for the two bones.
Results