Inverse relationship between the critical shoulder angle and rotator cuff insertional footprints: an anatomical study

Area of Science:

• Orthopedics
• Anatomy
• Biomechanics

Background:

• Degenerative shoulder disorders present significant clinical and economic challenges.
• The critical shoulder angle (CSA) predicts rotator cuff tears and osteoarthritis.
• The anatomical basis for CSA's predictive power is not fully understood.

Purpose of the Study:

• To investigate the correlation between the critical shoulder angle (CSA) and rotator cuff muscle insertional footprint size.

Main Methods:

• Anatomical study on 28 cadaveric shoulders.
• Measurement of the critical shoulder angle (CSA) using Grashey view radiographs.
• Dissection and measurement of supraspinatus (SSP), infraspinatus (ISP), teres minor (TM), and subscapularis (SSC) insertional footprints.

Main Results:

• A moderate inverse correlation was observed between CSA and the footprint size of all rotator cuff muscles.
• Specifically, ISP (r=-0.52), TM (r=-0.60), SSP (r=-0.51), and SSC (r=-0.42) showed significant inverse correlations.
• Larger CSA values were associated with smaller muscle insertional areas.

Conclusions:

• A large CSA is anatomically associated with smaller rotator cuff insertional footprints.
• These findings offer an anatomical basis for biomechanical models of shoulder pathology.
• This could enhance risk assessment and preventive strategies for shoulder disorders.