Background: Trochlear dysplasia is known to be an important cause of patellofemoral instability. D. Dejour’s radiographic and magnetic resonance imaging (MRI) classifications are widely used in clinical practice and in the orthopaedic literature to assess the severity of trochlear dysplasia. The indication for deepening trochleoplasty to treat trochlear dysplasia is also mainly based on the severity of trochlear dysplasia according to Dejour’s criteria.
Purpose: To our knowledge, there is no study evaluating the efficacy of the Dejour classification. The aim of this study was to assess the intraobserver and interobserver agreements of the radiographic and MRI-based classification as described by Dejour.
Study Design: Cohort study (diagnosis); Level of evidence, 2.
Methods: From 50 patients, 50 lateral radiographs as well as 50 MRI scans were read twice independently within 4 weeks by 4 surgeons (2 senior and 2 junior examiners). Analysis was made according to Dejour’s 4 grades of radiological criteria of trochlear dysplasia as well as differentiating between 2 grades: low-grade (type A) and high-grade trochlear dysplasia (types B-D).
Results: The 4-grade analysis showed fair intraobserver and interobserver agreements (24%-78%), while the 2-grade analysis showed good to excellent agreement (56%-96%). The best overall agreement was found for the 2-grade analysis on MRI scans (62%-96%). The lateral radiographs tended to underestimate the severity of trochlear dysplasia compared with axial MRI.
Conclusion: D. Dejour’s classification is valid for typing trochlear dysplasia and is particularly useful in separating low-grade from high-grade dysplasia.
Background
The tools for measuring the congruence angle with digital radiography software can be difficult to use; therefore, the authors sought to develop a new, easy, and reliable method for measuring patellofemoral congruence. The abstract goes here and covers two columns.
Hypothesis
The abstract goes The linear displacement measurement will correlate well with the congruence angle measurement. here and covers two columns.
Study Design
Cohort study (diagnosis); Level of evidence, 2.
Methods
On Merchant view radiographs obtained digitally, the authors measured the congruence angle and a new linear displacement measurement on preoperative and postoperative radiographs of 31 patients who suffered unilateral patellar dislocations and 100 uninjured subjects. The linear displacement measurement was obtained by drawing a reference line across the medial and lateral trochlear facets. Perpendicular lines were drawn from the depth of the sulcus through the reference line and from the apex of the posterior tip of the patella through the reference line. The distance between the perpendicular lines was the linear displacement measurement. The measurements were obtained twice at different sittings. The observer was blinded as to the previous measurements to establish reliability. Measurements were compared to determine whether the linear displacement measurement correlated with congruence angle.
Results
Intraobserver reliability was above r2 = .90 for all measurements. In patients with patellar dislocations, the mean congruence angle preoperatively was 33.5°, compared with 12.1 mm for linear displacement (r2 = .92). The mean congruence angle postoperatively was 11.2°, compared with 4.0 mm for linear displacement (r2 = .89). For normal subjects, the mean congruence angle was –3° and the mean linear displacement was 0.2 mm.
Conclusion
The linear displacement measurement was found to correlate with congruence angle measurements and may be an easy and useful tool for clinicians to evaluate patellofemoral congruence objectively.
