The impact of supraspinatus tear on subscapularis muscle atrophy and fatty infiltration.

Background: Aimed to report the prevalence and predisposing factors affecting subscapularis muscle atrophy and fatty infiltration (MAFI) in patients without a subscapularis tear, and to analyze the effect of this condition on surgical outcomes.

Methods: Between 2020 and 2022, 153 patients (mean age 58.1 ± 10.2 years; 84 men and 69 women) who underwent repair of posterosuperior cuff tears, with no subscapularis tears identified during arthroscopy were retrospectively analyzed. Baseline characteristics, preoperative and follow-up (6 months) magnetic resonance imaging findings, arthroscopic findings, and clinical outcomes (>1 year) were recorded.

Results: The prevalence of subscapularis MAFI (Goutallier grade 1 or 2) was 73.9% (113/153), of which the prevalence of Goutallier grade 2 was 23.5% (36/153). From multivariable logistic regression analysis, female sex (odds ratio [OR], 5.6; 95% CI, 1.7-18.6; P=0.005), older age (OR, 1.1; 95% CI, 1.0-1.1; P=0.052), advanced supraspinatus MAFI by Goutallier grade (OR, 3.2; 95% CI, 1.5-6.9; P=0.004), and synovitis (OR, 2.8; 95% CI, 1.1-7.9; P=0.030) were identified as independent predisposing factors for subscapularis MAFI. However, patients with preoperative subscapularis MAFI exhibited similar final range of motion, pain and function, and belly press strength compared to those without preoperative subscapularis MAFI.

Conclusions: Subscapularis MAFI is frequently observed conditions even in the absence of subscapularis tears, and this condition could be affected by supraspinatus MAFI, female sex, older age, and synovitis. However, because subscapularis MAFI does not affect the surgical outcome, surgeons need not be concerned about this condition when repairing posterosuperior rotator cuff tear. Level of evidence: IV.