Acute, Traumatic Rotator Cuff Tears Have Smaller Critical Shoulder Angles Than Degenerative Tears.

Area of Science:

• Orthopedic Surgery
• Shoulder Biomechanics
• Musculoskeletal Imaging

Background:

• The critical shoulder angle (CSA) is a radiographic measurement used to assess shoulder structure.
• Previous studies have described a specific CSA range for chronic degenerative rotator cuff tears (RCTs).
• The characteristics of the CSA in acute, traumatic RCTs remain less understood.

Purpose of the Study:

• To compare the critical shoulder angle (CSA) in patients with acute, traumatic rotator cuff tears (RCTs) to the established CSA in chronic degenerative RCTs.
• To investigate potential differences in shoulder anatomy between acute traumatic and chronic degenerative rotator cuff pathologies.

Main Methods:

• A multicenter retrospective analysis of 134 patients with acute, traumatic full-thickness RCTs was conducted.
• Preoperative advanced imaging and Grashey radiographs were used to measure the CSA and tear characteristics.
• Exclusion criteria included prior shoulder issues, overhead athletic activity, or significant fatty infiltration.

Main Results:

• The mean CSA in acute traumatic RCTs was 33.5°, significantly lower than the mean of 38.0° in degenerative tears.
• 60% of acute traumatic tears exhibited a CSA below the 35° threshold typically associated with degenerative tears.
• Older age and male sex were predictive of larger tear size, while older age and biceps avulsion predicted greater tear retraction.

Conclusions:

• Acute traumatic rotator cuff tears present with a smaller critical shoulder angle (CSA) compared to degenerative tears.
• The findings suggest that traumatic RCTs are a distinct pathological entity, not merely an acute exacerbation of chronic degeneration.
• This distinction supports the current clinical practice of managing traumatic RCTs differently from degenerative ones.