The minimal clinically important difference for function and strength in patients undergoing reverse shoulder arthroplasty

Abstract

Despite a statistically significant improvement in functional scores after receiving a reverse shoulder arthroplasty (RSA) in a cuff-deficient shoulder, not all patients perceive a minimal clinically important difference (MCID) in every functional domain of the score. This was a prospective longitudinal study including 60 consecutive patients with a cuff-deficient shoulder treated with a RSA. The Constant score was recorded before surgery and at a 1-year follow-up assessment. At the 1-year follow-up, all patients also filled out a 15-item anchor questionnaire to assess their perception of change in their overall function, forward elevation, lateral rotation, internal rotation, and strength to determine the MCID. The mean Constant score was 30.1 (standard deviation, 10.7) before surgery and was 58.4 (standard deviation, 16.2) at the 1-year follow-up, with statistically significant improvement (P < .001). A statistically significant improvement was found in the domains of forward elevation (P < .001), lateral rotation (P < .001), and strength (P < .001) except for internal rotation (P = .15). The MCID for overall function, forward elevation, lateral rotation, internal rotation, and strength in the Constant score increased by 8, 6, 2, 2, and 11.5 points, respectively; only 46.7%, 20%, 50%, 45.8%, and 33.3% of the patients, respectively, exceeded the MCID on each domain after surgery. A statistically significant improvement in the Constant score is expected after receiving an RSA in a cuff-deficient shoulder, but a considerable number of patients do not reach the MCID in the function and strength domains. A small improvement in rotation is perceived to be beneficial by patients, whereas large improvements in forward elevation are required for the improvement to be perceived to be beneficial.