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Assessing Trochlear Dysplasia With the Novel Lateral Trochlear Anterior Condyles Angle
Jason D Brenner1, Steven M Henick2, Leila Mehraban Alvandi1,2
1Albert Einstein College of Medicine, Bronx, New York, USA.
Background:
Trochlear dysplasia (TD) is considered by many to be an important risk factor for patellar dislocation (PD), and its accurate assessment is critical. Several methods to quantify TD exist, but none stand alone as the ideal measurement.
Hypothesis:
The authors hypothesized that a novel TD measurement, the lateral trochlear anterior condyles (LTAC) angle, is a simple yet comprehensive and reproducible technique for describing TD. Patients with PD will have lower LTAC angles (flatter trochlear groove [TG]) than controls; patients with recurrent PDs (RPDs) will have lower LTAC angles (flatter TG) than those with onetime PDs (OPDs).
Study Design:
Cross-sectional study; Level of evidence, 3.
Methods:
A retrospective case-control study was conducted of pediatric and adolescent patients with a history of PD versus a control group of age- and sex-matched patients (individuals with anterior cruciate ligament injuries but no history of PD). A subgroup analysis compared those with OPD versus RPDs. The LTAC angle was defined as the angle formed between (1) the lateral trochlear facet and (2) a line drawn connecting the most anterior portion of the medial and lateral femoral condyles. The LTAC angle was measured at 4 axial magnetic resonance imaging levels within the TG, assessing cartilaginous and osseous surfaces. LTAC mean differences were analyzed (all PDs vs controls; RPDs vs OPDs), and cutoffs for distinguishing all PDs from controls were based on the Youden index.
Results:
There were 170 patients (mean ± SD age, 15.29 ± 2.45 years; 58% female) with a history of PD (106 RPDs and 67 OPDs) and 98 controls (mean age, 15.56 ± 1.40 years; 47% female). Significant differences in mean LTAC values were observed between PD cases and controls at all levels of the TG on cartilaginous and osseous surfaces (P < .001). Patients with RPDs demonstrated significantly lower cartilaginous LTAC values than those with OPDs across all TG levels (P < .05), while osseous LTAC values showed no statistically significant differences at the proximal 3 axial levels (P > .05).
Conclusion:
The LTAC angle, a novel TD measurement, consistently shows lower values in PD cases as compared with controls throughout the TG. The LTAC angle combines the advantages of the lateral trochlear inclination angle and the sulcus angle (TG congruency) and assesses TD using a 1-image technique. The LTAC angle is a simple yet comprehensive measurement technique for TD that is able to stratify patients based on a history of PD events.
