Investigation of elevation strength relative to upper-limb muscle mass in dwelling older adults with asymptomatic rotator cuff tears

Background Many rotator cuff tears (RCTs) in community-dwelling older adults remain asymptomatic. Here, we compared shoulder elevation strength relative to upper-limb muscle mass in this population. Methods We analyzed 433 shoulders from 303 community-dwelling older adults without shoulder pain symptoms. RCTs were diagnosed using ultrasound imaging and classified into no tear (intact group); supraspinatus or infraspinatus tears (SSP/ISP group); and multiple tears, including the subscapularis (SSP/ISP + SSC group). The relative strength per muscle mass and relative strength per body mass were calculated. Results After applying the study criteria, 423 shoulders were analyzed: 358, 49, and 16 in the intact, SSP/ISP, and SSP/ISP + SSC groups, respectively. The mean strength-to-muscle mass ratios were 172.46 ± 55.87%, 150.41 ± 49.07%, and 107.47 ± 84.81% in the intact, SSP/ISP, and SSP/ISP + SSC groups, respectively. In the linear mixed-effects model, estimated relative strength per muscle mass tended to be lower in the SSP/ISP group than in the intact group; however, the difference was not statistically significant after Bonferroni adjustment. Shoulder elevation strength and relative strength per body mass did not differ significantly between the intact and SSP/ISP groups. No significant between-group difference was observed in upper-limb muscle mass. Conclusion This study did not provide confirmatory evidence of an association between rotator cuff tear classification and shoulder elevation strength relative to upper-limb muscle mass. However, relative strength per muscle mass may warrant further investigation as a complementary measure for identifying subtle functional differences that may not be apparent from absolute strength alone.