The usefulness of a newly developed ultrasonographic measurement method for predicting post-operative stiffness after arthroscopic rotator cuff repair.

BACKGROUND: Post-operative shoulder stiffness (POSS) is one of the most common complications following arthroscopic rotator cuff repair (ARCR) and is thought to be caused by pathologic 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 1 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 post-operatively. POSS was defined as passive external rotation <30° and forward elevation <120° at 12 months. Patients were assigned to 1 of the 2 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 curve analysis was also used to determine predictive thresholds values for POSS at 12 months after surgery, and intrarater and inter-rater reliability were assessed using intraclass correlation coefficients.

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 post-operatively. Regarding receiver operating characteristic curve analysis, the thresholds for POSS at 1 year post-operatively were 48% for the SSC sliding rate at 1 month after surgery, 38% for the SSC sliding rate at 3 months post-operatively, and 7° for UER at 3 months post-operatively. Reliability analysis showed substantial to almost perfect intrarater and inter-rater reliability for both SSC sliding rate and UER.

CONCLUSION: Early post-operative ultrasonographic evaluation is useful for predicting the development of POSS at 1 year after ARCR. Reduced SSC sliding rate and limited UER in the early post-operative period were significantly associated with subsequent POSS.