Undersurface rotator cuff repair for partial-thickness tears using the Opus knotless system: a prospective cohort of 1000 consecutive cases with a 1.4% retear rate

Background: Partial-thickness rotator cuff tears are a common cause of shoulder pain and disability. There are few large prospective cohort studies evaluating outcomes following arthroscopic repair, and reported structural failure rates vary widely across techniques. The purpose of this study was to (1) evaluate the structural and clinical outcomes of an arthroscopic undersurface knotless inverted mattress repair for partial-thickness rotator cuff tears, (2) assess the effect of surgical experience on outcomes, and (3) place these outcomes in the context of published series of alternative techniques. Methods: A prospectively collected cohort of 1000 consecutive patients with articular- or bursal-sided partial-thickness supraspinatus tears >50% thickness underwent arthroscopic repair using the Opus knotless system (Smith & Nephew) with an undersurface knotless inverted mattress technique. Structural integrity was assessed using ultrasound at a minimum of 6 months. Pain, range of motion, and strength were assessed pre-operatively and at 6 weeks, 12 weeks, and 6 months. A learning curve was identified, with retear rates peaking at 5% between cases 100-200 and declining to ≤1% after approximately 200 cases. Conclusion: Arthroscopic undersurface knotless inverted mattress repair of partial-thickness rotator cuff tears achieved a retear rate of 1.4%, with no reoperations for infection or post-operative stiffness and consistent improvements across all clinical outcome measures. Retear rates declined after approximately 200 cases, a pattern consistent with a learning-curve effect, although this descriptive moving-average analysis is exploratory and was not subjected to formal change-point modeling. The favorable structural outcomes and short operative time observed with this technique may relate, in part, to minimal disruption of the remaining tendon and subacromial bursa and the direct intra-articular visualization afforded by this undersurface approach.