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Changes in pennation angle in rotator cuff muscles with torn tendons
Jianlin Zuo1, Hirotaka Sano, Eiji Itoi
1Department of Orthopaedic Surgery, China-Japan Union Hospital of Jilin University, Changchun, China.
Summary
Rotator cuff tears alter muscle pennation angles, with larger tears causing greater increases in the supraspinatus and infraspinatus muscles. This study quantifies these changes in cadaveric shoulders.
Area of Science:
- Orthopedic Surgery
- Musculoskeletal Anatomy
- Biomechanical Research
Background:
- Pennation angles of intact rotator cuff muscles are documented.
- The link between altered pennation angles and rotator cuff tears requires further clarification.
Purpose of the Study:
- To measure pennation angles in human cadaveric rotator cuff muscles with tendon tears.
- To investigate the relationship between tear size and pennation angle alterations.
Main Methods:
- Compared pennation angles in 10 rotator cuff tear shoulders versus 10 intact control shoulders.
- Measured pennation angles from digital images of dissected rotator cuff muscles.
- Statistically analyzed correlations between tear size and pennation angles of supraspinatus and infraspinatus muscles.
Main Results:
- Significantly greater pennation angles were observed in the supraspinatus and infraspinatus muscles of the tear group compared to the control group.
- Positive correlations were found between pennation angle and tear size (length and area) for both supraspinatus and infraspinatus muscles in full-thickness tears.
- Partial-thickness tears did not significantly affect pennation angles.
Conclusions:
- Pennation angles of rotator cuff muscles increase with the size of the tear.
- Tear size is a significant factor influencing pennation angle changes in rotator cuff injuries.
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