Biceps Femoris Long-Head Architecture Assessed Using Different Sonographic Techniques.

PURPOSE: To assess the repeatability of, and measurement agreement between, four sonographic techniques used to quantify biceps femoris long head (BFlh) architecture: i) static-image with linear extrapolation technique; ii) extended field-of-view (EFOV) with linear ultrasound probe path (linear-EFOV) using either a straight or segmented analyses; and iii) EFOV with nonlinear probe path and segmented analysis (nonlinear-EFOV) to follow the complex fascicle trajectories.

METHODS: Twenty individuals (24.4±5.7 years; 175±0.8 cm; 73±9.0 kg) without history of hamstring strain injury were tested in two sessions separated by 1-hour. An ultrasound scanner coupled with 6-cm linear probe was used to assess BFlh architecture in B-mode.

RESULTS: The ultrasound probe was positioned at 52.0±5.0% of femur length and 57.0±6.0% of BFlh length. We found an acceptable repeatability when assessing BFlh fascicle length (ICC3,k = 0.86-0.95; SEM = 1.9-3.2 mm) and angle (ICC3,k = 0.86-0.97; SEM = 0.8-1.1) using all sonographic techniques. However, the nonlinear-EFOV technique showed the highest repeatability (fascicle length ICC3,k = 0.95; fascicle angle, ICC3,k = 0.97). The static-image technique, which estimated 35.4±7.0% of the fascicle length, overestimated fascicle length (8-11%) and underestimated fascicle angle (8-9%) compared to EFOV techniques. Also, the rank order of individuals varied by ~15% between static-image and nonlinear-EFOV (segmented) when assessing the fascicle length.

CONCLUSIONS: Although all techniques showed good repeatability, absolute errors were observed using static-image (7.9±6.1 mm for fascicle length) and linear-EFOV (between 3.7±3.0 and 4.2±3.7 mm), probably because the complex fascicle trajectories were not followed. The rank order of individuals for fascicle length and angle were also different between static-image and nonlinear-EFOV, so different muscle function and injury risk estimates could likely be made when using this technique.