The Usefulness of Newly Developed Ultrasonographic Measurement Method for Predicting Postoperative Stiffness after Arthroscopic Rotator Cuff Repair

Introduction Postoperative shoulder stiffness (POSS) is one of the most common complications following arthroscopic rotator cuff repair (ARCR) and is thought to be caused by pathological changes in the anterosuperior soft-tissue structures of the glenohumeral joint. The aim of this study was to determine whether objective ultrasonographic evaluation can predict the occurrence of POSS at one year after surgery and to investigate the reliability of a newly developed ultrasonographic measurement method. Methods This retrospective cohort study included patients who underwent ARCR at a single institution between April 2017 and June 2018. Ultrasonographic external rotation (UER) and the subscapularis (SSC) sliding rate, representing anterosuperior soft-tissue sliding mobility assessed by ultrasonography, were evaluated at 1 and 3 months postoperatively. POSS was defined as passive external rotation <30° and forward elevation <120° at 12 months. Patients were assigned to one of the two groups: Group N (without POSS) or Group S (with POSS). Propensity score matching was performed to minimize baseline differences between groups. UER and SSC sliding rate were compared between the groups. Receiver operating characteristic (ROC) curve analysis was also used to determine predictive thresholds values for POSS at 12 months after surgery, and intra- and inter-rater reliability were assessed using intraclass correlation coefficients (ICCs). Results After propensity score matching, 40 shoulders (20 per group) were analyzed. The SSC sliding rate at 1 and 3 months and UER at 3 months were significantly greater in Group N than in Group S. The greatest between-group difference was observed for the SSC sliding rate at 1 month postoperatively. Regarding ROC curve analysis, the thresholds for POSS at one year postoperatively were 48% for the SSC sliding rate at 1 month after surgery, 38% for the SSC sliding rate at 3 months postoperatively, and 7° for UER at 3 months postoperatively. Reliability analysis showed substantial to almost perfect intra- and inter-rater reliability for both SSC sliding rate and UER. Conclusion Early postoperative ultrasonographic evaluation is useful for predicting the development of POSS at one year after ARCR. Reduced SSC sliding rate and limited UER in the early postoperative period were significantly associated with subsequent POSS. Level of Evidence Level III, Retrospective Cohort Design, Prognosis Study