Assessing gluteus medius volume with freehand 3DUS: validating a practical imaging tool for complex muscle morphology

Area of Science:

• Musculoskeletal imaging
• Biomedical engineering
• Anatomy

Background:

• Accurate muscle morphology assessment is crucial for clinical and research applications.
• Existing imaging techniques may have limitations in accessibility or applicability to complex muscle structures.
• The gluteus medius (GMed) muscle's complex shape presents challenges for volumetric analysis.

Purpose of the Study:

• To evaluate the validity and reliability of freehand three-dimensional ultrasound (3DUS) using a multiple-sweep technique for GMed muscle volume measurement.
• To compare 3DUS measurements against magnetic resonance imaging (MRI) as the reference standard.
• To assess the intra- and inter-processor reliability of the 3DUS method.

Main Methods:

• Twelve healthy participants underwent both 3DUS and MRI scans of the GMed.
• 3DUS utilized three overlapping sweeps for volumetric data acquisition.
• Independent segmentation of 3DUS and MRI images by two processors to calculate muscle volume.
• Bland-Altman analysis for agreement between 3DUS and MRI; ICC, CV%, TE, and MDC for reliability assessments.

Main Results:

• Minimal mean difference observed between 3DUS and MRI, with good agreement and no systematic bias.
• Excellent inter- and intra-processor reliability for 3DUS measurements (ICC = 0.972 and 0.999, respectively).
• Good between-position reliability (ICC = 0.94) was found in a subgroup analysis comparing prone and side-lying positions.

Conclusions:

• Freehand 3DUS with a multiple-sweep technique is a valid and reliable method for measuring GMed muscle volume.
• This 3DUS approach offers a practical and accessible alternative to MRI for both clinical and research settings.
• The technique demonstrates high consistency across different processors and measurement positions.