The critical shoulder angle (CSA) has been proposed as a cause of degenerative rotator cuff tears, but all prior evidence was retrospective and cross-sectional. This longitudinal study of asymptomatic cuff tears asks whether the CSA can be reliably measured, whether it tracks with tear size, whether it predicts tear enlargement, and whether it changes over time. It tries to sort out whether the CSA is a cause or an effect of cuff disease.
Do not use the critical shoulder angle to predict which asymptomatic cuff tear will grow, and do not counsel a patient toward surgery based on a high CSA alone.
This paper is the first longitudinal look at the CSA, and it directly attacks the causation problem that plagued the earlier cross-sectional studies. A causal driver of cuff disease should predict tear size and progression and should be stable over time. The CSA is stable, but it fails to predict size or progression, so the authors read it as at most a weak marker, not a cause.
The 2° difference they found is smaller than in prior work, and they credit their Suter-Henninger radiograph quality control for that. When you read older CSA papers, ask whether radiograph quality was controlled, because a poorly positioned scapula distorts the angle by roughly the same 2° that separated their groups.
The practical lesson: cuff degeneration is largely an age-related intrinsic tendon process, and skeletal morphology is a smaller player than the extrinsic-impingement theory once claimed.
The critical shoulder angle (CSA) has been proposed as a cause of degenerative rotator cuff tears, but all prior evidence was retrospective and cross-sectional. This longitudinal study of asymptomatic cuff tears asks whether the CSA can be reliably measured, whether it tracks with tear size, whether it predicts tear enlargement, and whether it changes over time. It tries to sort out whether the CSA is a cause or an effect of cuff disease.
Do not use the critical shoulder angle to predict which asymptomatic cuff tear will grow, and do not counsel a patient toward surgery based on a high CSA alone.
This paper is the first longitudinal look at the CSA, and it directly attacks the causation problem that plagued the earlier cross-sectional studies. A causal driver of cuff disease should predict tear size and progression and should be stable over time. The CSA is stable, but it fails to predict size or progression, so the authors read it as at most a weak marker, not a cause.
The 2° difference they found is smaller than in prior work, and they credit their Suter-Henninger radiograph quality control for that. When you read older CSA papers, ask whether radiograph quality was controlled, because a poorly positioned scapula distorts the angle by roughly the same 2° that separated their groups.
The practical lesson: cuff degeneration is largely an age-related intrinsic tendon process, and skeletal morphology is a smaller player than the extrinsic-impingement theory once claimed.