How repaired rotator cuff function influences Constant scoring

Area of Science:

• Orthopedic Surgery
• Shoulder Biomechanics
• Musculoskeletal Research

Background:

• The functional contribution of an intact rotator cuff to shoulder function, particularly the Constant score, is not fully understood.
• Rotator cuff integrity is crucial for shoulder stability and movement, but the extent of its influence on functional outcomes requires clarification.

Purpose of the Study:

• To evaluate the functional influence of an intact rotator cuff on the unweighted Constant score and its components.
• To determine the relationship between rotator cuff fatty degeneration and shoulder function.

Main Methods:

• Analysis of 29 non-osteoarthritic shoulders with intact sutured rotator cuff tears after a 9-year follow-up.
• Assessment of rotator cuff fatty degeneration index (FDI) and Constant scores.
• Application of linear regression analysis to correlate FDI with Constant scores.

Main Results:

• A strong negative correlation was observed between preoperative and follow-up FDI and all Constant scores.
• The impact of intact repaired rotator cuff function became negligible when FDI exceeded 2.25.
• Other shoulder muscles, including the deltoid, provide basic shoulder function (approx. 62 Constant score) when rotator cuff function is compromised.

Conclusions:

• Shoulder muscles other than the rotator cuff are responsible for approximately 60% of the unweighted Constant score, providing basic shoulder function.
• Lower FDI indicates greater improvement in basic function provided by an intact repaired rotator cuff.
• The findings are supported by similar Constant scores in reverse shoulder prostheses and painless shoulders with full-thickness rotator cuff tears.