Do subscapularis tears really result in superior humeral migration?

Area of Science:

• Orthopedic Surgery
• Musculoskeletal Imaging
• Shoulder Biomechanics

Background:

• Superior humeral excursion (SHE) and acromiohumeral distance (AHD) are critical indicators of shoulder joint health.
• Rotator cuff tears, particularly those involving the supraspinatus and subscapularis tendons, can significantly impact shoulder biomechanics.

Purpose of the Study:

• To analyze the effect of subscapularis tears on superior humeral excursion (SHE) and acromiohumeral distance (AHD).
• To test the hypothesis that subscapularis tears do not result in superior humeral excursion.

Main Methods:

• A diagnostic study (Level III) involving shoulder arthroscopy patients (2011-2015).
• Patients were categorized into four groups: isolated Bankart lesion, isolated supraspinatus tear, isolated subscapularis tear, and combined tear.
• Magnetic resonance imaging (MRI) was used to measure SHE and AHD, comparing these measurements across groups to assess superior humeral migration (SHM).

Main Results:

• Thirty patients were included in each of the four groups.
• Group 1 (Bankart lesion) and Group 3 (subscapularis tear) showed higher mean AHD and SHE compared to Group 2 (supraspinatus tear) and Group 4 (combined tear).
• AHD and SHE demonstrated a strong positive correlation (Pearson correlation coefficient = 0.184), with excellent inter-observer and intra-observer reliability for SHE measurements on MRI.

Conclusions:

• Isolated subscapularis tears do not lead to superior humeral migration (SHM) or subacromial impingement.
• Superior rotator cuff tears, even with an intact subscapularis tendon, can cause SHM and subacromial impingement.