Longitudinal Changes in the Range of Motion of the Shoulder and Scapular Function of Patients Undergoing Reverse Total Shoulder Arthroplasty and Their Relationship with Preoperative Factors

[Purpose] To investigate changes in shoulder range of motion (ROM) and scapular motion over time after reverse total shoulder arthroplasty (RTSA), and to identify preoperative factors that influence them. [Participants and Methods] Thirty-four shoulders were observed for at least 24 months after RTSA. The scapular rotational angles of scapular supination were calculated as 45° abduction (SI45) and supination (SI0) on the scapular plane, and the difference (ΔSI) between the two. The changes in ROM and SI over time and the influence of preoperative factors on SI45 at 6 and 24 months postoperatively were investigated. [Results] Flexion and abduction improved at all postoperative time points. The only independent variable for SI45 at 6 and 24 months postoperatively was preoperative SI45. [Conclusion] Scapular motion decreased postoperatively, but preoperative scapular motion continued to be an influence at 6 and 24 months postoperatively.