No decrease of muscle strength, function and exercise found after reverse shoulder arthroplasty follow-up

Purpose: To assess muscle strength and the correlation with physical functioning, pain, time interval since surgery and self-reported exercise after reverse shoulder arthroplasty (RSA). Materials and methods: Fourteen patients with primary RSA (mean age 68.9 years; mean follow-up 48.6 months), were assessed twice within a 9-month interval. Outcome measures were the Bostrom function test, the Shoulder Pain and Disability Index (SPADI), isometric strength measured with a handheld dynamometer, and the self-reported amount of specific shoulder exercises. Results: The mean isometric strength did not significantly change on the operated side over 9 months (flexion: -1.6 N, p = .638; abduction: 6.1 N, p = .433) nor between the operated and nonoperated sides (flexion: 5.1 N, p = .551; abduction: 2.8 N, p = .826). There was no significant correlation between strength and time interval since surgery or self-reported amount of exercise. Abduction strength showed a small to moderate correlation with SPADI at baseline (-0.529, p = .05) and the Bostrom function score at follow-up (0.573, p = .05). Strength difference between the operated and nonoperated sides for abduction showed a small to moderate correlation with the Bostrom pain score at baseline (-0.565, p = .05). Conclusions: In this study, we found that strength after RSA did not decrease over time and was not associated with self-reported exercise. A small to moderate correlation was found between absolute strength in abduction and SPADI at baseline and the Bostrom function score at follow-up. Strength difference between the operated and nonoperated sides for abduction showed a small to moderate correlation with the Bostrom pain score at baseline.