Reliability and validity of a standardised ultrasound examination protocol to quantify vastus lateralis muscle.
Theresa Maria Betz, Michaela Wehrstein, Fabian Preisner and 2 others
PMID 34121129WHAT IT FOUND
Ultrasound reliably measures vastus lateralis thickness in people with varying body fat.
Thickness readings match MRI well. However, cross-sectional area measurements become less accurate as subcutaneous fat increases, so clinicians should not rely on ultrasound area data for patients with higher body fat.
Key findings
01Ultrasound measurements of muscle thickness showed excellent reliability and good agreement with MRI, regardless of subcutaneous fat thickness.
02Ultrasound measurements of muscle cross-sectional area showed lower agreement with MRI, and this inaccuracy increased significantly with greater subcutaneous fat thickness.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only 16 healthy subjects and did not include patients with known sarcopenia, morbid obesity, or elite athletes. The reliability and validity of the measurements in people with extreme body compositions remain unknown. Ultrasound was performed with a roll under the knees, which may affect muscle relaxation compared to the MRI position.
Declared interests
No specific funding sources or conflicts of interest are explicitly declared in the provided text, though equipment manufacturers (GE Healthcare, Siemens) are named.
The easy way to misread this
Do not assume that all ultrasound muscle measurements are equally accurate. While muscle thickness is reliable, cross-sectional area measurements are significantly less accurate in patients with higher subcutaneous fat.