Reliability of Ultrasound Measurements in the Assessment of Femoral Trochlear Morphology in Healthy Adolescents

Background/Objectives: CT and MRI are standard modalities for assessing femoral trochlear morphology. Ultrasound may also be useful, as it allows visualization of both the femoral trochlear cartilage and the subchondral bone surface. We aimed to investigate the reliability of ultrasound measurements of femoral trochlear morphology. Methods: This was a pilot study including healthy adolescents. Two examiners sequentially performed ultrasound examinations to assess inter-rater reliability, and one week later the first examiner repeated the examination to assess intra-rater reliability. The following measurements were obtained using the contours of the trochlear cartilage and subchondral bone as reference points: sulcus angle, trochlear depth, trochlear facet asymmetry, and ventral trochlear prominence. Results: There were 35 participants (16 males and 19 females) with a mean age of 15.1 years (range, 11.1–18.2 years). Inter-rater reliability was moderate to excellent, with ICCs of 0.78–0.89 for bony and 0.67–0.91 for cartilaginous measurements. Intra-rater reliability was also moderate to excellent, with ICCs of 0.66–0.91 for bony and 0.73–0.94 for cartilaginous measurements. Sulcus angle and trochlear depth were the most reliable measurements, followed by ventral trochlear prominence, whereas trochlear facet asymmetry was less consistent. Bland–Altman analysis showed small mean differences and narrow 95% limits of agreement for both inter-rater and intra-rater reliability. Conclusions: Sulcus angle, trochlear depth, trochlear facet asymmetry, and ventral trochlear prominence can be reliably measured using ultrasound in healthy adolescents. Overall measurement reliability varies depending on the raters, the specific parameter measured, and whether bony or cartilaginous landmarks are used, but is generally good.