Isokinetic strength differences between patients with primary reverse and total shoulder prostheses: muscle strength...

Area of Science:

• Orthopedic surgery
• Biomechanics
• Rehabilitation

Background:

• Total shoulder arthroplasty (TSA) offers better range of motion than reverse shoulder arthroplasty (RSA), yet clinical outcomes are comparable.
• Investigating differences in force-generating capacity between TSA and RSA is essential.

Purpose of the Study:

• To compare isokinetically produced joint torques between RSA and TSA.
• To determine if force-generating capacity correlates with functional outcomes in RSA and TSA patients.

Main Methods:

• 18 RSA patients and 12 TSA patients underwent isokinetic testing for abduction/adduction and external/internal rotation at 60°/s.
• Pre- and post-operative Constant-Murley scores were collected for functional assessment.

Main Results:

• TSA patients demonstrated significantly higher ab-/adduction and ex-/internal rotation torques compared to RSA patients.
• RSA patients showed significant correlations between strength and external rotation torques with functional scores.
• TSA patients exhibited moderate to strong correlations between strength and rotational torques with functional sub-scores.

Conclusions:

• Shoulders treated with TSA exhibit superior strength compared to those treated with RSA.
• The reduced strength in RSA may be attributed to rotator cuff muscle absence and a medialized center of rotation.
• External rotation strength is a key predictor of functional outcomes in RSA patients.