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Updated: Jul 6, 2025
10:10
Reverse Total Shoulder Arthroplasty
Published on: July 5, 2011
43.2K
External Rotation Strength After TSA in Osteoarthritic Shoulders with Eccentric Deformity Is Not Impacted by
Margaret S Coats-Thomas1,2,3, Guido Marra4, Daniel Ludvig1,2
1Biomedical Engineering, Northwestern University, Evanston, Illinois.
JB & JS Open Access
|January 10, 2024
Summary
Total shoulder arthroplasty (TSA) patients with eccentric deformity did not show external rotation weakness. However, reduced infraspinatus activity suggests persistent posterior rotator cuff deficiency after TSA in these patients.
Area of Science:
- Orthopedic surgery
- Biomechanics
- Shoulder reconstruction
Background:
- Total shoulder arthroplasty (TSA) is an option for persistent glenohumeral osteoarthritis.
- Higher TSA revision rates are noted in patients with eccentric glenoid deformity compared to concentric.
- Persistent posterior rotator cuff deficiency may contribute to TSA failures.
Purpose of the Study:
- To investigate if patients with eccentric glenoid deformity exhibit relative external rotation weakness after TSA.
- To determine if this potential weakness is linked to posterior rotator cuff deficiency.
Main Methods:
- Prospective recruitment of patients over 1 year post-TSA for osteoarthritis.
- Measurement of torque and electromyography during isometric contractions.
- Comparison of strength balance and rotator cuff muscle activity between eccentric and concentric deformity groups.
Main Results:
- No significant difference in relative external rotation strength was found between eccentric and concentric deformity groups.
- Patients with eccentric deformity showed reduced infraspinatus activity (43.9% MVC) compared to concentric (51.3% MVC).
Conclusions:
- Relative external rotation weakness was not observed after TSA in patients with eccentric deformity.
- Reduced infraspinatus activity indicates potential persistent posterior rotator cuff deficiency.
- Further longitudinal studies are needed to assess muscle imbalance and TSA failure rates.
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