Subscapularis re-tears associated with preoperative advanced fatty infiltration and greater subscapularis involvement, leading to inferior functional outcomes and decreased acromiohumeral distance.

PURPOSE This study aimed to investigate the influence of repaired subscapularis integrity on midterm results for anterosuperior massive rotator cuff tears (MRCTs) treated with partial rotator cuff repair. METHODS This study included 57 patients who underwent arthroscopic partial repair for an anterosuperior MRCT. They were assigned to the healed subscapularis group (Group H 37 patients) or subscapularis re-tear group (Group R 20 patients). Preoperative and postoperative functional scores and active ranges of motion (ROMs) were assessed. Preoperative and 6-month follow-up magnetic resonance arthrography (MRA)/computed tomography arthrography (CTA) images were compared between groups. RESULTS At the final follow-up, mean functional shoulder scores including ROMs improved significantly in both groups compared to preoperative values (p < 0.001), except for forward flexion and internal rotation in Group R. All final functional values and ROMs (excluding external rotation) were better in Group H than in Group R (p < 0.001). Preoperative stage of fatty infiltration in the subscapularis muscle was significantly worse in Group R (p < 0.001). On follow-up MRA/CTA, the immediate residual defect after partial repair increased in 81% (30/37; mean, 17.8 mm) of patients in Group H and 100% (mean 24.6 mm) in Group R (p < 0.001). At final follow-up, mean acromiohumeral distance significantly decreased from 8.2 to 6.0 mm in Group H (p < 0.001) and from 8.3 to 4.9 mm in Group R (p < 0.001). There was a significant difference in final acromiohumeral distance between groups (p < 0.001). CONCLUSION After a minimum 5-year follow-up after arthroscopic partial repair of anterosuperior MRCT, subscapularis re-tear was identified in 35% of patients (20/57) on early postoperative follow-up MRA/CTA. The subscapularis re-tear group exhibited more preoperative advanced fatty infiltration and greater extents of subscapularis involvement, which led to statistically inferior functional outcomes and decreased acromiohumeral distance at final follow-up. Nonetheless, in terms of a minimal clinically important difference, substantial clinical benefit, and patient-acceptable symptomatic state for clinical significance, there were no significant differences between the groups. LEVEL OF EVIDENCE III.