Evaluation of trochlear dysplasia using MRI: correlation between the classification system of Dejour and objective parameters of trochlear dysplasia

Abstract

Quantitative measurements of the femoral trochlea have shown to be of limited value for the assessment of trochlear dysplasia. None of the quantitative measurements of the trochlea on transverse images could be assigned to the four-grade descriptive classification of trochlear dysplasia of Dejour. Additionally, measurements could not be reliably performed in high-grade trochlear dysplasia. However, trochlear inclination, trochlear facet asymmetry and depth of trochlear groove may help to distinguish between low-grade and high-grade dysplasia.

Are the Current Classifications and Radiographic Measurements for Trochlear Dysplasia Appropriate in the Skeletally Immature Patient?

“…7 Additionally, there are inconsistences in the adult literature regarding the inter- and intraobserver agreement of the Dejour classification as well as poor correlation between the objective measurements of trochlear dysplasia and the Dejour classification. 12,13,17 …”

Patient-specific modeling of the trochlear morphologic anomalies by means of hyperbolic paraboloids

“…[14] This finding is in agreement with recent works in the literature reporting that morphometric parameters can optimistically discriminate between the Grade A and the three remaining grades. [15,16] Equivalently, the Dejour classification was shown to be meaningfully effective in separating low-grade from high-grade cases. There are however two main clinical issues that are not adequately addressed by such a technique.…”

“…The main advantage is that the model provides a continuous representation of morphologic variations in HP parameter space taking into account the full geometrical complexity of trochlea unlike the traditional morphometric parameters, as the trochlear depth or the sulcus angle, which basically encode the shape variation into a single axial plane. [2,16,17] This approach is novel in the literature with respect to alternative 3D techniques based on statistical shape models that in contrast cannot easily correlated parameter variations with specific morphologic features. [29,30] Second, we found that similar morphologic anomalies of the trochlear aspect, as encoded by similar HP parameters, are actually attributed to different severity grades in the Dejour classification.…”

“…However, this grading has been extensively questioned in the literature due to difficulty in clustering the large variability of the morphologic anomalies into such specific classes, suggesting that morphometric measures can yield more reliable criteria to score the anomaly degree. [2,16,17] Morphometric parameters, such as the trochlear depth, the sulcus angle, the lateral trochlear facet inclination and the trochlear facet asymmetry ratio, to cite the most relevant, are based on anatomical landmarks manually digitized in computed tomography (CT) and magnetic resonance (MR) images. [12,[18][19][20][21] The use of such parameters have been criticized as well because of difficulties in the precise localization of landmarks, especially in case of large morphologic deviations, [20] dependency on the adopted measurement protocol [2,5,17] and interobserver variability.…”

“…The work aims at showing that similar morphologic anomalies, encoded by homogeneous HP parameters, are actually identified with different grades of Dejour dysplastic severity, thus restating that the difference among the grades, according to qualitative signs of the trochlear aspect, cannot be simply mapped to monotonic variations of morphometric parameters as recently hypothesized in the literature. [15,16] Distal femur surfaces of symptomatic patients (aspecific anterior knee pain) were retrospectively included in this study to verify the hypothesis.…”