Atrophy patterns in isolated subscapularis lesions

Area of Science:

• Orthopedics
• Radiology
• Musculoskeletal Imaging

Background:

• Existing methods for supraspinatus atrophy lack characterization for isolated subscapularis muscle atrophy.
• Subscapularis (SSC) muscle atrophy patterns following isolated SSC tendon repair require detailed description.

Purpose of the Study:

• To describe patterns of subscapularis muscle atrophy after isolated SSC tendon repair.
• To establish a reliable and reproducible method for quantifying subscapularis atrophy using MRI.

Main Methods:

• Analyzed MRI scans from 49 controls and 11 patients with isolated SSC tears.
• Measured subscapularis cross-sectional area (CSA) and calculated the ratio of the upper half CSA to total CSA.
• Defined bony landmarks for accurate CSA measurement and assessed inter-rater reliability.

Main Results:

• Control group mean CSA ratio was 0.446 (±0.046).
• Subscapularis repair group showed a significantly lower mean CSA ratio of 0.269 (±0.065) (p < 0.05).
• The CSA ratio demonstrated reliability and reproducibility in quantifying atrophy.

Conclusions:

• The subscapularis muscle cross-sectional area (CSA) ratio is a reliable tool for quantifying atrophy.
• Proposed a classification for subscapularis atrophy: Stage I (<0.4), Stage II (<0.35), and Stage III (<0.3).
• This classification aids in assessing the severity of subscapularis muscle atrophy post-repair.