A three-dimensional approach to pennation angle estimation for human skeletal muscle

Area of Science:

• Biomechanics
• Anatomy
• Medical Imaging

Background:

• Pennation angle (PA) is crucial for skeletal muscle force generation.
• Two-dimensional (2D) ultrasonography is the standard method for measuring PA.
• Inferring 3D muscle architecture from 2D ultrasound is challenging due to complexity and variation.

Purpose of the Study:

• To investigate the accuracy of 2D ultrasound in assessing PA compared to 3D muscle architecture.
• To develop a reliable 3D method for quantifying PA based on geometric analysis.

Main Methods:

• Developed a 3D method using dissection and digitization of cadaveric muscle specimens.
• Acquired 3D architectural data.
• Simulated 2D ultrasound imaging from the 3D data for comparative analysis.
• Based the 3D method on geometric analysis of fascicle attachment for consistency.

Main Results:

• Significant discrepancies observed between 2D and 3D PA measurements, ranging from 1.1% to 47.1%.
• 2D ultrasound can either underestimate or overestimate PA depending on the specific muscle architecture.

Conclusions:

• Direct 3D quantification provides a more accurate assessment of pennation angle.
• Relying solely on 2D ultrasound may lead to inaccuracies in understanding muscle function and force contribution.