The Relationship Between Body Mass Index and Fatty Infiltration in the Shoulder Musculature

Fatty infiltration in the rotator cuff muscles has been well studied in the setting of rotator cuff tendon tears to help predict outcomes of surgical repair. Fatty infiltration in the rotator cuff has also been independently correlated to the variables of age and sex. The purpose of our study was to determine if there is a relationship between body mass index and fatty infiltration in patients with no imaging evidence of rotator cuff tendinosis or tear.

Radiology reports of all magnetic resonance imaging examinations of the shoulder were searched over a 2-year period. Studies with imaging findings of rotator cuff tendinosis, partial tear, or full thickness tear were excluded from the study, resulting in a total of 143 patients with normal rotator cuffs who were included in the study. These studies were reviewed by consensus by 2 fellowship-trained musculoskeletal radiologists who used the Goutallier 5-stage scoring system to grade the supraspinatus, infraspinatus, subscapularis, teres minor, teres major, and deltoid muscles.

Sex was shown not to be significantly associated with fatty infiltration with the exception of the deltoid muscle, which showed a statistically significant increase in fatty infiltration associated with female sex (P = 0.038). Age was shown to be a statistically significant predictor of fatty infiltration for all 6 muscles (P < 0.05). Body mass index was shown to be a statistically significant predictor of fatty infiltration for all of the evaluated shoulder musculature (P < 0.05) with the exception of the teres minor.

Our results suggest that increased body mass index is associated with increased fatty infiltration in the supraspinatus, infraspinatus, subscapularis, teres major, and deltoid muscles. This relationship could help guide the decisions of orthopedic surgeons when considering rotator cuff repair.