Histological findings 4 weeks after tendon-to-bone repair. (A) Repair only. (B) Repair + CS. (C) Repair + P407 (Picrosirius red; magnification, ×100). Immature collagen fragments are stained in green. As the maturation and organization of collagen fibers increased, the green staining changed to yellow and subsequently to orange at the repaired tendon-to-bone site. More cellular organization, more collagen fibers, and increased maturity of collagen fibers were observed in the repair + P407 specimens than in the repair only and the repair + CS specimens. White arrows indicate collagen fibers. Scale bars, 100 μm.