The Destiny of the Subscapularis Tendon after Arthroscopic Supraspinatus Repair

Background: The purpose of this study was to identify the changes in untreated subscapularis in patients who underwent supraspinatus repair and to evaluate the factors related to the changes in the subscapularis. Methods: A cohort of patients who underwent isolated supraspinatus repair with preservation of the subscapularis was reviewed. Changes in the subscapularis, including any newly formed lesion and aggravation of an existing lesion, were evaluated 12 months postoperatively on magnetic resonance imaging along with an examination to identify causative factors after supraspinatus repair. Clinical scores were compared between patients with and without subscapularis changes. Results: A total of 528 patients were reviewed. Changes in the subscapularis, including newly formed lesions and aggravation of an existing lesion, were shown in 90 patients (17.0%). Upon regression analysis, changes in the subscapularis were associated with the initial existence of a subscapularis lesion (grade I: p = 0.042, grade II: p = 0.025), an accompanying biceps lesion (p = 0.038), and a retear of the repaired supraspinatus (p = 0.024). No significant differences were shown in clinical scores between patients with and without subscapularis changes after supraspinatus repair. Conclusions: Untreated asymptomatic subscapularis may undergo morphological changes even after repair of the torn supraspinatus. Preoperative subscapularis lesions, biceps long head pathology, and retears of the repaired supraspinatus were associated with subscapularis pathology in patients who underwent supraspinatus repair.