Does Undergoing a Prehabilitation Protocol Aimed at Optimizing Scapulothoracic Mobility and Strengthening Improve Internal Rotation After Reverse Shoulder Arthroplasty? A Randomized Controlled Trial

Reverse total shoulder arthroplasty (RSA) provides excellent restoration of overhead motion and pain relief, with durability demonstrated up to 20-years postoperatively.6 However, despite advancements in surgical technique and implants, internal rotation (IR) remains challenging for many patients after RSA, with a recent study demonstrating as many as 63% of patients reporting significant difficulty or inability to perform some activities of daily living (ADLs) requiring IR.5

Many studies have been conducted to identify demographic, surgical, and implant-related predictors of improved IR after RSA. To date, the only consistent predictor of superior IR after RSA in the literature is more favorable preoperative IR. Nearly all interventions that have been evaluated to improve IR after RSA focus on glenohumeral relationships, such as repairing the subscapularis, increasing humeral component anteversion, and preventing impingement between the humeral polyethylene and the scapular neck. However, IR is a complex shoulder movement involving motion beyond the glenohumeral joint, including scapulothoracic, sternoclavicular, acromioclavicular, and truncal motion.

Studies evaluating shoulder girdle mechanics during abduction and forward elevation after RSA have shown increased dependence on scapulothoracic motion to compensate for less glenohumeral motion. Furthermore, Sulkar et al. performed bi-plane fluoroscopy to compare shoulder kinematics in low and high IR performers after RSA. Patients in the high rotation group had 7° greater scapular upward rotation and used a 15°-30° change in scapular tilt to perform IR in adduction, whereas tilt barely changed (<5°) in most patients in the low group. Interestingly, scapular notching occurred at similar rates in high and low performing cohorts, suggesting that scapular motion can compensate for bony impingement at the glenohumeral joint.

It stands to reason that a prehabilitation program focused on strengthening internal rotators and improving patients' neuromuscular control of the scapula may enable them to adapt more effectively to the altered biomechanics of RSA, and improve their ability to perform ADLs that require IR. Previous studies have demonstrated a moderate correlation between patients' preoperative shoulder strength and range of motion and their postoperative function. However, to date, no studies have attempted to determine whether preoperative improvement in shoulder mobility and strength might confer a durable improvement in shoulder function after RSA, particularly in IR. In the lower extremity, meta-analyses of randomized controlled trials of the total knee arthroplasty literature have found superior knee range of motion and sit-to-stand test performance in patients that underwent a prehabilitation program compared to controls.

The overarching objective is to assess the impact of prehabilitation IR strengthening and mobility on patients undergoing RSA. The specific aim of this study is to determine whether a preoperative rehabilitation program aimed at strengthening shoulder internal rotators and improving scapular mobility can improve patient-reported ability to perform IRADLs postoperatively, as evaluated using the Activities of Daily Living which require Internal Rotation (ADLIR) score.