180 / 460
179
Introduction
Trochlear dysplasia is known to be an important
cause for patellofemoral instability. Henri
Dejour
et al.
[11] found that 96% of patients
with a history of a true patellar dislocation had
evidence of trochlear dysplasia.
The lateral X-ray has always been a necessary
part of the radiographic evaluation of the knee.
Not only is it critical for assessing patellar
height [2] but in 1989Walch and H. Dejour [25]
as well as 1992 Grelsamer and Tedder described
the lateral trochlear sign [14] bringing to light
its value in diagnosing trochlear dysplasia.
In addition to the lateral trochlear sign, which
he later called crossing sign, H. Dejour
described the supratrochlear bump or spur and
the double contour as typical radiological signs
of trochlear dysplasia [11].
H. Dejour
et al.
[10, 11] initially described
three types of trochlear dysplasia on conven
tional lateral radiographs. Due to the lack of
intra- and interobserver agreement, D. Dejour
later proposed his classification of four types
on two-dimensional radiographs and three-
dimensional CT-scans (fig. 1) [8, 9].
Recently magnetic resonance imaging has
become the diagnostic tool of choice to assess
patellofemoral instability, because soft tissue
injuries, potential flake fractures and the tibial
tuberosity groove distance can also be eva
luated [1, 7, 21, 22, 23]. On axial MRI trochlear
dysplasia is diagnosed on the first craniocaudal
image, where the complete cartilaginous
trochlea can be seen.
Dejour’s radiographic and axial CT
classifications [11] are widely used in clinical
practice and in the orthopaedic literature to
assess the severity of trochlear dysplasia [6, 13,
19, 21]. The aim of this study was to assess the
intra- and interobserver agreement of the
radiographic and MRI based classification as
described by D. Dejour.
Intra- and Interobserver
agreement of Dejour´s
classification of trochlear
dysplasia
S. Lippacher, H. Reichel, M. Nelitz