The critical shoulder angle does not change over time: a radiographic study.

Area of Science:

• Orthopedic surgery
• Radiology
• Anatomy

Background:

• Scapular anatomy can influence shoulder pathologies.
• The critical shoulder angle (CSA) is a key anatomical measurement.
• Long-term stability of the CSA in adults is not well-established.

Purpose of the Study:

• To determine if the critical shoulder angle (CSA) changes over long-term follow-up.
• To assess if scapular morphology is a stable parameter in adults.
• To investigate the influence of aging on scapular morphology.

Main Methods:

• Analysis of shoulder radiographs from 2002-2019 with at least a 10-year interval.
• Measurement of the critical shoulder angle (CSA).
• Assessment of acromion type, posterior acromial height, and posterior acromial tilt.

Main Results:

• The mean CSA remained stable at 34° between initial and follow-up assessments (P = .597).
• Posterior acromial height was stable (P = .186), while posterior acromial tilt showed a significant change (P < .001).
• CSA stability was observed irrespective of rotator cuff tear status.

Conclusions:

• The critical shoulder angle (CSA) is a stable anatomical parameter in adults after physeal closure.
• Scapular morphology, specifically the CSA, does not significantly change with age.
• These findings have implications for understanding shoulder biomechanics and pathology development.