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Since biomechanical studies have shown the
MPFL as the main restraint against lateral
patellar displacement [4, 6], MPFL-recons
truction became a widely accepted technique to
restore normal patellar tracking and stability [5,
9, 10]. Although the clinical outcome studies
after MPFL reconstruction report promising
results related to stability, there are some cases,
reporting about increased pain or loss of function
postoperatively [8, 11, 13, 15, 16]. Main reason
therefore seems to be a non-anatomical
reconstruction, since the importance of correct
graft positioning for ligament reconstruction has
been recognized already in 1938 by Palmer [12],
and its influence on the clinical outcome is well
known in ACL reconstruction [1]. While the
patellar insertion, where the medial facet can be
prepared completely, even with relatively small
skin incisions, the femoral insertion, which is
described to be close to the medial epicondlye
and the adductor tubercle can be difficult to
palpate, not only when covered by soft tissue,
but also in skinny patients.
Since biomechnical studies [2, 7] have shown
the influence of a non-anatomical femoral
insertion onto the patelllofemoral pressure, this
insertion became the key point in MPFL
reconstruction.
The reason for this estimated increase of medial
patellofemoral pressure is founded by the idea
that a too proximal fixation point would lead to
an increased distance to the patella, when the
knee flexes, and vice versa for a too posterior
attachment [2], a proper tunnel placement is
necessary to restore physiological kinematics
and pressure postoperatively.
However, although numerous studies have
focused the MPFL anatomy in preparation
studies, guidelines for a intraoperative use for
minimal invasive surgery is missing. Compared
to ACL reconstruction, where radiographic
guidelines for proper tunnel placement were
given to improve clinical results [3], same
guidelines are mandatory for an anatomical
MPFL reconstruction, achieving not only
stability, but also full range of motion/function
without presence of patellofemoral pain by
increasing the retropatellar pressure [2, 7, 15].
In this work, a proper radiographic landmark is
demonstrated to identify the anatomical femoral
MPFL insertion intraoperatively or to use it as
a postoperative control.
To initially verify this point, a number of eight
cadavers have been prepared and the center of
the femoral MPFL insertion have been
identified and marked with a radiodense ball
with a small diameter. Then, a straight lateral
view, with both posterior condyles projected in
the same plane, were taken and the position of
Importance and Radiographic
Identification of the
Femoral Insertion in Medial
Patellofemoral Ligament
Reconstruction
P.B. Schoettle