Biomechanical and Magnetic Resonance Imaging Evaluation of a Single- and Double-Row Rotator Cuff Repair in an In Vivo Sheep Model

Purpose: To investigate the biomechanical and magnetic resonance imaging (MRI)-derived morphologic changes between single- and double-row rotator cuff repair at different time points after fixation. Methods: Eighteen mature female sheep were randomly assigned to either a single-row treatment group using arthroscopic Mason-Allen stitches or a double-row treatment group using a combination of arthroscopic Mason-Allen and mattress stitches. Each group was analyzed at 1 of 3 survival points (6 weeks, 12 weeks, and 26 weeks). We evaluated the integrity of the cuff repair using MRI and biomechanical properties using a mechanical testing machine. Results: The mean load to failure was significantly higher in the double-row group compared with the single-row group at 6 and 12 weeks (P = .018 and P = .002, respectively). At 26 weeks, the differences were not statistically significant (P = .080). However, the double-row group achieved a mean load to failure similar to that of a healthy infraspinatus tendon, whereas the single-row group reached only 70% of the load of a healthy infraspinatus tendon. No significant morphologic differences were observed based on the MRI results. Conclusions: This study confirms that in an acute repair model, double-row repair may enhance the speed of mechanical recovery of the tendon-bone complex when compared with single-row repair in the early postoperative period. Clinical Relevance: Double-row rotator cuff repair enables higher mechanical strength that is especially sustained during the early recovery period and may therefore improve clinical outcome.