When and how much does the muscle strength recover after arthroscopic superior capsular reconstruction?

Background: Recently, arthroscopic superior capsular reconstruction (SCR) has been performed for irreparable large to massive rotator cuff tears and excellent clinical results have been reported. Although the muscle strength is reported to recover, it has not yet been clarified when and how much it recovers. The purpose of this study was to determine the recovery pattern of muscle strength after SCR. Methods: We retrospectively reviewed 35 patients (mean age, 65 years) who met the following inclusion criteria: (1) patients with large to massive irreparable tears of the rotator cuff including the supraspinatus and infraspinatus tendons; (2) those with severe muscle atrophy and fatty change; (3) those who underwent assessment of muscle quality and strength by magnetic resonance imaging and dynamometry at 6 months, 1 year, and 2 years; (4) those with a minimum follow-up period of 2 years; and (5) those without severe osteoarthritis. The isometric muscle strength of scaption (ie, scapular-plane elevation), internal rotation, and external rotation in adduction was measured twice for each motion by a dynamometer. Results: Relative to the muscle strength on the uninvolved side, the involved side showed 61% +/- 21% in scaption, 63% +/- 20% in external rotation, and 103% +/- 29% in internal rotation at 2 years after surgery. Whereas no significant differences were observed between the 1 -year and 2 -year follow-up assessments, a significant difference in muscle strength of scaption was found between 6 months and 1 year (P = .0174). Graft retear was seen in 5 cases (14%). There was a trend that the muscle strength of scaption and external rotation in the no-retear group was greater than that in the retear group despite no significant difference (P = .0717 and P = .0824, respectively). Conclusion: The recovery of the muscle strength after SCR was observed until 1 year after surgery, and the muscle strength of scaption and external rotation returned to 60% of that on the uninvolved side at 2 years. Level of evidence: Level IV; Case Series; Treatment Study (c) 2023 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.