The functional internal rotation scale: a novel shoulder arthroplasty outcome measure

Background: Shoulder arthroplasty, especially reverse shoulder arthroplasty (RSA), continues to increase in volume. Limitations in internal rotation can be challenging following RSA. Current patient-reported outcome measures are limited in assessing a patient's functional internal rotation following shoulder arthroplasty. To address this limitation, a questionnaire was developed. Methods: A single-center prospective comparative cohort study was performed to determine the reliability of the questionnaire. A pilot group of patients who had at least 1 year of follow-up following shoulder arthroplasty was asked to complete the questionnaire. Reliability testing was performed using Cronbach's alpha test. Additionally, individual questions and total questionnaire scores were compared between patients who underwent anatomic total shoulder arthroplasty (TSA) and RSA. Results: The questionnaire showed high reliability with all questions. A group of 23 anatomic TSA and 20 RSA patients were compared. RSA patients scored significantly lower on the questionnaire (35.2 out of 50 vs. 43.9, P =.001). Conclusion: The questionnaire can be used in conjunction with other patient-reported outcome measures to help surgeons better assess patients' results following shoulder arthroplasty. The initial findings from our internal reliability study found that RSA patients had significantly lower scores and higher variability in internal rotation function vs. patients with TSA. Further studies are needed to determine the clinical importance of this questionnaire.