Abstract
BACKGROUND: Atrophy and fatty infiltration of the supraspinatus (SS) muscle are prognostic indicators of poor functional outcomes and higher retear rates after rotator cuff repair. While older patients, female patients, and those with massive and retracted rotator cuff tears are at a higher risk for these indicators, it is unclear whether tear characteristics, acromion morphology, and acromioclavicular (AC) joint arthritis affect SS atrophy in older patients with chronic shoulder pain. PURPOSE: To investigate the multifactorial influences associated with SS atrophy in rotator cuff tears. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A review was conducted on 391 patients with atraumatic shoulder pain (mean age, 60.88 ± 8 years; range, 50-93 years; 200 men and 191 women) who underwent magnetic resonance imaging between May 2019 and April 2020. SS atrophy was calculated using the occupation ratio. Logistic regression was performed to evaluate the association of SS atrophy with patient age and sex, rotator cuff tear type (partial- vs full-thickness), anteroposterior (AP) tear size, AC and glenohumeral (GH) joint arthritis, and acromion shape. A subgroup analysis was performed in patients without tears to investigate whether SS atrophy and fatty infiltration were independent phenomena. RESULTS: Overall, 91 patients had full-thickness tears without retraction, 131 had partial-thickness tears, and 169 had no tears. The prevalence of SS atrophy was associated with patient age and was more prevalent in women (67.6%), full-thickness tears (91.1%), an AP tear size of >15 mm (92.6%), and GH joint arthritis (100%) (P < .001 for all). The severity of atrophy (indicated by a decrease in the occupation ratio) increased with older age. In the patients without tears, SS atrophy prevalence was 33.1%. Logistic regression analysis showed significant independent associations of SS atrophy with age (P < .001), female sex (P < .001), nonretracted full-thickness tears (P < .001), an AP tear size of >15 mm (P < .001), and hook-shaped acromion (P = .007). A subgroup analysis of the nontear group revealed a significant association of SS atrophy with fatty infiltration (P < .001). CONCLUSION: This study identified significant associations between SS atrophy and older age, female sex, full-thickness tear without retraction, an AP tear size of >15 mm, and hook-shaped acromion. Notably, partial-thickness tears were not significantly associated with SS atrophy.