Abstract
We investigated the validity of panoramic ultrasound (US) compared to magnetic resonance imaging (MRI) for the assessment of hamstrings cross-sectional area (CSA) and volume. Hamstrings CSA were acquired with US (by an expert operator) at four different sites of femur length (FL) in 85 youth competitive alpine skiers (14.8 ± 0.5 years), and successively compared to corresponding scans obtained by MRI, analyzed by a trained vs. a novice rater. The agreement between techniques was assessed by Bland–Altman analyses. Statistical analysis was carried out using Pearson’s product moment correlation coefficient (r). US-derived CSA showed a very good agreement compared to MRI-based ones. The best sites were 40% FL (0 = mid patellar point) for biceps femoris long head (r = 0.9), 50% for semitendinosus (r = 0.9), and 30% for semimembranosus (r = 0.86) and biceps femoris short head (BFsh, r = 0.8). US-based vs. MRI-based hamstrings volume showed an r of 0.96. Poorer r values were observed for the novice compared to the trained rater, with the biggest difference observed for BFsh at 50% (r = 0.001 vs. r = 0.50, respectively) and semimembranosus at 60% (r = 0.23 vs. r = 0.42, respectively). Panoramic US provides valid CSA values and volume estimations compared to MRI. To ensure optimal US-vs.-MRI agreement, raters should preferably possess previous experience in imaging-based analyses.
Highlights
The assessment of skeletal muscle size is central within many athletic performance and clinical scenarios
Pearson’s correlation coefficient ranged from 0.64–0.86 for SM (p < 0.0001 for all region of interest (ROI)), from 0.84–090 for ST (p < 0.0001 for all ROIs), from 0.75–0.90 for biceps femoris long head (BFlh) (p < 0.0001 for all ROIs), and from 0.37–080 for BFsh (p < 0.0001 for 30% and 40% ROIs, p < 0.01 for 50% ROI)
Over the specific ROI in which the scans were acquired, maximal cross-sectional area (CSA) measured from magnetic resonance imaging (MRI) was 8.09 ± 2.19 for SM located at the 40%, 8.64 ± 2 for ST located at the 50%, 10.36 ± 2.19 for BFlh located at the 50%, and 5.71 ± 1.38 for BFsh located at the 30%
Summary
The assessment of skeletal muscle size is central within many athletic performance and clinical scenarios. MRI is not cheap and not always accessible as other imaging techniques[9], especially in athletic-related settings, when many measures should be acquired over time (and preferably independently of fixed imaging facilities) in order to meticulously monitor the athletic development process or the successfulness of return to sport programs In such context, ultrasound (US) could represent a cheaper, yet reliable alternative for the quantification of muscle size. In the specific context of competitive alpine skiers, hamstrings muscles play an especially important role, as they may act as an ACL-synergist by producing a posteriorly directed shear force to the tibia (i.e., by eccentrically resisting the boot-induced anterior drawer of the tibia relative to the femur that is known to be typical for skiing-related ACL injury mechanisms)[21,22,23,24] In all of these examples, the US-based evaluation of hamstrings CSA and volume may serve as a meaningful monitoring tool
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