Long-term follow-up of patients with a high critical shoulder angle and acromion index: is there an increased retear risk after arthroscopic supraspinatus tendon repair?

BACKGROUND: The effect of the acromion index (AI) and critical shoulder angle (CSA) on the short-term healing rate after arthroscopic repair of the supraspinatus tendons is already known. Long-term effects have not been published yet. PURPOSE: Long-term evaluation of the effect of the AI and CSA on the postoperative healing rate and clinical results after arthroscopic repair of the supraspinatus tendon. METHODS: Patients with a symptomatic, single-tendon, full-thickness supraspinatus tear in whom nonoperative management had failed were treated with an arthroscopic repair. Preoperative radiographs were used to measure CSA and AI. Eight years postoperatively, magnetic resonance imaging (MRI) studies were performed and evaluated on repair integrity. Patient-reported outcome measurements were collected pre- and postoperatively. RESULTS: Thirty-one patients were evaluated 8 years postoperatively. The mean age at the time of surgery was 61 ± 9 years. MRI evaluation showed that 20 patients (65%) had an intact repair and 11 (35%) had a full-thickness retear. No significant differences were found between the intact and retear groups regarding age (P = .605), initial tear size (P = .485), retraction grade (P = .439), and all PROMs. The mean CSA for the intact group (33° ± 1°) was significantly lower than the CSA in the retear group (38° ± 1°; P = .004). Eighteen patients (58%) had a CSA ≥35°, and 9 (50%) among them had a retear and 9 (50%) had an intact repair. The mean AI for the intact group (0.72 ± 0.11) was significantly lower than the AI in the retear group (0.81 ± 0.08 ; P = .021). Seventeen patients (55%) had an AI ≥0.75, and 9 (53%) among them had a retear and 8 had an intact repair. If the AI was ≥0.75, the odds ratio of having a retear was 6.19 (P = .045). No progressive worsening of PROMs and clinical results could be demonstrated related to a higher CSA or AI during the entire follow-up. CONCLUSION: At long-term follow-up, a higher CSA has the tendency to have an increased rate of retear after arthroscopic supraspinatus tendon repair, but this was not significant. A higher AI significantly increased the retear risk. A higher CSA and AI did not impair the clinical results over time. An AI ≥0.75 was associated with a 6-fold increase in risk of retear after arthroscopic supraspinatus tendon repair.