Degradable magnesium alloy suture promotes fibrocartilaginous interface regeneration in a rat rotator cuff transosseous repair model

Despite transosseous rotator cuff tear repair using sutures is widely accepted for tendon-bone fixation, the fibrocartilaginous enthesis regeneration is still hardly achieved with the traditional sutures. In the present work, degradable magnesium (Mg) alloy wire was applied to suture supraspinatus tendon in a rat acute rotator cuff tear model with Vicryl Plus 4–0 absorbable suture as control. The shoulder joint humerus-supraspinatus tendon complex specimens were retrieved at 4, 8, and 12 weeks after operation. The Mg alloy suture groups showed better biomechanical properties in terms of ultimate load to failure. Gross observation showed that hyperplastic response of the scar tissue at the tendon-bone interface is progressively alleviated over time in the both Mg alloy suture and Vicryl suture groups. In the histological analysis, for Mg alloy suture groups, chondrocytes appear to proliferate at 4 weeks postoperatively, and the tendon-bone interface showed an orderly structural transition zone at 8 weeks postoperatively. The collagenous fiber tended to be aligned and the tendon-bone interlocking structures apparently formed, where transitional structure from unmineralized fibrocartilage to mineralized fibrocartilage was closer to the native fibrocartilaginous enthesis. In vivo degradation of the magnesium alloy wire was completed within 12 weeks. The results indicated that Mg alloy wire was promising as degradable suture with the potential to promotes fibrocartilaginous interface regeneration in rotator cuff repair.