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Structural properties of the subscapularis tendon.
A Halder1, M E Zobitz, E Schultz
1Orthopedic Biomechanics Laboratory Mayo Clinic/Mayo Foundation, Rochester, Minnesota 55905, USA.
Summary
Glenohumeral joint stability varies regionally within the subscapularis tendon. The superior portion is stiffer and stronger, potentially protecting against tears, while the inferior portion
Area of Science:
- Orthopedic Surgery
- Biomechanics
- Anatomy
Background:
- The subscapularis muscle is crucial for glenohumeral joint movement and stability.
- Understanding its tendon's structural properties is vital for diagnosing and treating shoulder pathologies.
Purpose of the Study:
- To investigate regional differences in subscapularis tendon structural properties.
- To assess the influence of glenohumeral joint position on these properties.
Main Methods:
- Cadaveric shoulder subscapularis tendons were sectioned into superior, midsuperior, midinferior, and inferior parts.
- Tendon sections were mechanically tested to failure at 0 and 60 degrees of glenohumeral abduction.
Main Results:
- Arm position significantly affected tendon stiffness, with regional variations observed.
- The inferior tendon region exhibited lower stiffness and ultimate load compared to superior regions.
- The superior and midsuperior portions demonstrated higher stiffness and failure loads in both tested positions.
Conclusions:
- Regional differences in subscapularis tendon properties influence rotator cuff tear patterns and glenohumeral instability.
- The robust superior region may resist tear progression, while the weaker inferior region could be implicated in anterior shoulder dislocations.
- Surgical repair of the inferior subscapularis tendon is recommended for glenohumeral instability.