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Patellofemoral disorders are a transversal link
in knee pathologies. They present with a wide
range of symptoms from pain and feeling of
instability to documented episodes of true
patellar dislocation. This special pathology
gives symptoms from childhood and
adolescence with a high-demand in sports
activities to the degenerative arthritic knee.
One of the least understood pathologies in an
otherwise thoroughly studied knee joint is
patellar dislocation. Patients with recurrent
patellar dislocation experience a disabling
everyday life, are predisposed to future
patellofemoral arthritis and the causes of
dislocation and arthritis seem to overlap [1-3].
A huge volume of surgical and bibliographic
interest on the treatment of this disease has
enriched the orthopedic literature. In the last
decades the surgeons’ arsenal gained new
techniques on both soft-tissue and bony
surgeries. But even after many different
operations on these patients, there is still a
small subgroup of this population with near-to-
normal knee kinematics or even unsatisfactory
post-operative results [3]. This is probably
attributed to the multifactorial cause of patellar
dislocation and the inability to provide to all of
these patients a definitive treatment with the
present techniques [1, 3].
The causes of patellar dislocation include bony
abnormalities, soft-tissue trauma or even anato
mical abnormalities and impaired function of
the surrounding musculature [1, 3, 4]. Although
patellar dislocation leads to deficiency of the
medial patellofemoral ligament (MPFL), the
medial patellomeniscal ligament (MPML) and
the medial patellotibial ligament (MPTL) [5],
whose chief role in patellar stability is clear [3,
6, 7], the principal causes of dislocation are
osseous anomalies [4]. Their importance lies
on the fact that patellar dislocation has been
associated with threshold values of their normal
anatomy, and therefore the amount for their
surgical correction has been identified [4, 8].
MPFL rupture or elongation is the consequence
of patellar dislocation, while the basic causes
of patellar dislocation are anatomic anomalies
such as trochlea dysplasia, patella alta and
extensor mechanism malalignment [3, 4, 8-11].
All of them have to be well identified in order
to correct the primitive anatomic anomalies
and to repair the
consequence
of patellar
dislocation.
Regardless of the age of onset or the pattern
(permanent, habitual or recurrent) of patellar
dislocation, four main anatomic anomalies with
statistical thresholds have been identified in
this population since 1987 [12]: trochlear
dysplasia, patella alta, excessive trochlear
groove-tibial tuberosity distance (TT-TG) and
excessive lateral patellar tilt are the underlying
key factors predisposing to instability [4].
The history of the trochlear
dysplasia in patella
dislocation
D. Dejour, P.G. Ntagiopoulos