Intra- and Inter-Rater Reliability of Ultrasound Imaging to Measure Tensor Fasciae Latae Muscle Size

Objectives: The objectives of this study were to develop a procedure to measure the cross-sectional area and thickness of tensor fasciae latae muscle, and examine the intra- and inter-rater reliability of this procedure in healthy participants. Methods: The cross-sectional area and thickness of tensor fascia latae were evaluated by sonography in 14 healthy subjects (28 lower extremities) in a single session. Two examiners conducted ultrasound examinations and performed the measurements independently. Each examiner was blinded to the measurements of the other examiner. For examination, the transducer was placed transversally to the thigh at the anterior superior iliac spine level and was moved caudally along the tensor fascia latae muscle, ensuring that the volume of the muscle was in the center of the image. The examiners took ultrasound images when the maximum size was reached. Results: The intra-rater reliability for tensor fascia latae measurements was excellent in both examiners (cross-sectional area: ICC2,2 = 0.905-0.969, SEM = 0.29-0.82 mm², MDC = 0.80-2.27; thickness: ICC2,2 = 0.965-0.985, SEM = 0.20-0.60 mm, MDC = 0.55-1.66; all p < 0.001). The inter-rater reliability was good for the cross-sectional area (ICC2,2 = 0.783, SEM = 0.77 mm², MDC = 2.13 mm²). The inter-rater reliability was poor for thickness measurements (ICC2,2 = 0.445, SEM = 2.12 mm, MDC = 5.87 mm) and 2.12 mm for thickness. Conclusions: The procedure developed for measuring the size of the tensor fascia latae muscle with ultrasound images has demonstrated feasibility and excellent intra-rater reliability. The inter-rater reliability was good and poor for cross-sectional area and thickness measurements, respectively.