[Diffusion Tensor Imaging of Rotator Cuff: Influence of Arm Position]

Area of Science:

• Musculoskeletal imaging
• Biomedical engineering
• Orthopedic research

Background:

• Diffusion tensor imaging (DTI) characterizes muscle physiology and microstructure.
• Rotator cuff DTI indices can vary with muscle contractile state and forearm position.

Purpose of the Study:

• To investigate the effect of forearm position on DTI indices in rotator cuff muscles.
• To analyze changes in fractional anisotropy (FA) and mean diffusivity (MD) across different forearm positions.

Main Methods:

• DTI scans of the right rotator cuff were performed in nine healthy volunteers.
• Scans were acquired in neutral, external rotation, and internal rotation forearm positions.
• FA and MD values were calculated and compared between positions for each muscle.

Main Results:

• Significant differences in FA and MD were observed between external and internal rotation for infraspinatus, teres minor, and subscapularis.
• These variations are attributed to altered muscle fiber cross-sectional area and contractile state.
• Increased diffusion of intercellular water along the short axis (increased λ2 and λ3) influences FA and MD.

Conclusions:

• Forearm position demonstrably affects DTI indices in rotator cuff muscles.
• Muscle contraction state, influenced by forearm position, alters DTI measurements.
• DTI is sensitive to the biomechanical changes within the rotator cuff during different functional positions.