Comparison of Dynamic In Vivo Shoulder Kinematics Before and After Superior Capsular Reconstruction for Irreparable Rotator Cuff Tears

BACKGROUND: Superior capsular reconstruction (SCR) is an alternative surgical option for young active patients with irreparable rotator cuff tears without arthritis. Although cadaveric studies have shown superior stability of the humerus, it remains unclear whether the humerus migrates superiorly after SCR in vivo. PURPOSE: To analyze the change in glenohumeral translation in patients before and after SCR. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A total of 22 patients who underwent SCR by a single surgeon for irreparable rotator cuff tears were included. Among them, 14 patients had intact grafts, and 8 patients were diagnosed with retears on 1-year postoperative magnetic resonance imaging (MRI) scans. Fluoroscopy was performed in all patients preoperatively and at 3-month, 6-month, and 1-year follow-up. Moreover, 3-dimensional bone models from computed tomography, MRI, and fluoroscopic scans during scapular plane abduction of the shoulder joints were analyzed. RESULTS: In the intact graft group, 3-dimensional dynamic shoulder kinematics at 6 months (P = .026) and 1 year (P = .032) postoperatively showed statistically significant decreases in humeral head superior translation compared with preoperatively. The ≥6-mm acromiohumeral distance (AHD) subgroup had a larger decrease in humeral head superior translation from preoperatively than did the <6-mm AHD subgroup (6 months: P = .026; 1 year: P = .032). The retear group had significantly greater humeral head superior translation at 1 year postoperatively than did the ≥6-mm and <6-mm AHD subgroups (post hoc test: P < .001; ≥6-mm AHD vs retear group: P = .001; <6-mm AHD vs retear group: P = .012). CONCLUSION: SCR with intact grafts resulted in decreased humeral head superior translation after 6 months. Patients with retears showed no improvement in humeral head superior translation. Patients with a preoperative AHD <6 mm had less improvement in humeral head superior translation than did those with a preoperative AHD ≥6 mm. Early surgical treatment before an excessive decrease in preoperative AHD could be helpful for postoperative humeral head translation recovery.