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Published on: September 28, 2018
Glenohumeral stability in simulated rotator cuff tears
F Steenbrink1, J H de Groot, H E J Veeger
1Department of Orthopaedics, Leiden University Medical Center, The Netherlands.
Journal of Biomechanics
|May 20, 2009
Summary
Rotator cuff tears disrupt shoulder force balance, impacting arm elevation. Massive tears compromise stability, requiring specific muscle actions like adverse adductor co-contraction to maintain joint integrity.
Area of Science:
- Biomechanics
- Orthopedics
- Musculoskeletal Research
Background:
- Rotator cuff tears disrupt shoulder biomechanics, affecting arm elevation torques and the glenohumeral joint.
- The relationship between glenohumeral torque generation and joint stability following rotator cuff tears remains unclear.
Purpose of the Study:
- To investigate the trade-off between glenohumeral torque and stability in simulated rotator cuff tears.
- To understand compensatory muscle activation patterns required to maintain glenohumeral stability after injury.
Main Methods:
- Utilized inverse dynamic simulation (Delft Shoulder and Elbow Model) to estimate muscle forces.
- Simulated five combinations of rotator cuff tears in a single arm position.
- Assessed glenohumeral stability by ensuring the glenohumeral reaction force intersected the glenoid surface.
Main Results:
- An isolated supraspinatus tear minimally increased muscle effort (8%) without causing instability.
- Massive tears (beyond supraspinatus) led to significant instability, with deltoids unable to fully compensate lost abduction torque.
- The subscapularis and biceps longum showed unfavorable compensatory roles, while the teres minor was crucial for stability.
- Adverse adductor muscle co-contraction was essential for preserving glenohumeral stability.
Conclusions:
- Glenohumeral instability is a prominent factor in massive rotator cuff tears.
- Specific muscles (teres minor) and compensatory actions (adductor co-contraction) are vital for maintaining shoulder joint stability after significant rotator cuff injury.
