In vivo shoulder kinematic changes and rotator cuff healing after surgical repair of large-to-massive rotator cuff tears

Background: Few studies have investigated the correlation between shoulder kinematics and clinical outcomes in patients undergoing rotator cuff repair using dynamic analysis. This study assessed shoulder kinematics before and after surgical repair in patients with rotator cuff tears (RCTs) and determined the relationship among shoulder kinematics and between shoulder kinematics and clinical outcomes.

Methods: Ten patients with large-to-massive RCTs and 10 control participants were included. In vivo shoulder kinematics during scapular plane abduction were measured preoperatively and 1 year postoperatively using validated image-registration techniques and compared among the control, preoperative, and postoperative groups. Mixed models were used to compare the effects of the groups on shoulder kinematics, followed by Tukey's honest significant difference test. Pearson's correlation coefficient was used to identify the correlations among shoulder kinematics and between each kinematic and clinical outcome.

Results: The scapula, tilted more anteriorly preoperatively, was not different from the control group postoperatively. Additionally, the change in scapular posterior tilt (PT) throughout dynamic abduction was 18.17° ± 3.59° in the postoperative group, greater than that in the control group (11.54° ± 2.29°; p = 0.0037). The postoperative change in PT significantly correlated with acromiohumeral distance (AHD) and rotator cuff integrity (Sugaya classification) (AHD: r = 0.71, p = 0.023; Sugaya classification: r = - 0.75, p = 0.013), but not preoperative change in PT. Functional score improved from preoperative to postoperative (p < 0.0001). Abduction angle and functional score significantly correlated with Sugaya classification (abduction angle: r = - 0.67, p = 0.034; functional score: r = - 0.70, p = 0.025) but not with shoulder kinematics. Mean superior translation of the humeral head and AHD throughout abduction changed from 1.77 ± 1.34 to 0.61 ± 1.37 and 1.44 ± 1.59 to 2.71 ± 2.27 mm, respectively, from preoperative to postoperative (both p < 0.0001).

Conclusions: After the surgical repair of large-to-massive RCTs, glenohumeral stability normalized, and the more anteriorly tilted orientation of the scapula improved. Additionally, the preoperative increased scapular motion throughout dynamic abduction was further enhanced postoperatively. Interestingly, in postoperative patients, scapular motion toward PT during dynamic abduction correlated with minimum AHD and cuff healing.