Ultrasound-measured patellar tendon-trochlear groove distance: A reliable and valid method with moderate correlation to computed tomography-based knee lateralization parameters

To evaluate the reliability and validity of ultrasound-measured patellar tendon-trochlear groove (USPT-TG) distance as a novel method for assessing knee lateralization, and to determine its correlation with conventional computed tomography (CT)-based measurements, including the tibial tubercle-trochlear groove (TT-TG), patellar tendon-trochlear groove (PT-TG) and tibial tubercle-posterior cruciate ligament distances.

This cross-sectional study included patients who had undergone knee surgeries within the period from February 2023 to January 2024. The USPT-TG measurements were performed using ultrasound imaging, 1 cm distal to the inferior patellar border. Inter-rater and intra-rater reliabilities were assessed using intra-class correlation coefficients (ICCs). Correlations between the USPT-TG and CT-based parameters were analyzed using Pearson's correlation coefficient, and measurement agreement was evaluated using the Bland-Altman analysis.

A total of 75 patients (47 females and 28 males) with a mean age of 51.0 ± 23.5 years were included in this study. The USPT-TG demonstrated excellent intra-rater reliability (ICC: 0.98, 95% confidence interval [CI]: 0.97-0.99) and good inter-rater reliability (ICC: 0.82, 95% CI: 0.75-0.88). The USPT-TG had a strong correlation with the PT-TG (r = 0.71, p < 0.0001) and a moderate correlation with the TT-TG (r = 0.42, p = 0.0002). The mean measurements were: USPT-TG, 8.3 ± 2.8 mm; TT-TG, 12.5 ± 3.5 mm and PT-TG, 9.0 ± 2.9 mm. The Bland-Altman analysis showed acceptable agreement between the inter-rater reliability of the USPT-TG distance (bias: 0.59 ± 2.21 mm, 95% limits of agreement [LOA]: -3.73 to 4.92 mm), USPT-TG versus TT-TG measurements (bias: 4.20 ± 3.47 mm, 95% LOA: -2.61 to 11.01 mm) and USPT-TG versus PT-TG measurements (bias: -0.71 ± 2.17 mm, 95% LOA: -4.96 to 3.54 mm).

The USPT-TG is a reliable and valid method for assessing knee lateralization and demonstrates a moderate-to-strong correlation with the TT-TG and PT-TG measurements. This radiation-free technique may offer a practical alternative to traditional imaging methods, particularly in settings where radiation exposure should be minimized or access to advanced imaging is limited. Further research is needed to establish the diagnostic thresholds and validate this technique in patients with patellar instability.

Level II.