Fig. 4

Histopathological findings of graft tissue taken by biopsy at 13 months postoperatively. a Gross view of the graft tissue showing cartilagenous tissue. Hematoxylin and eosin (b, d-f) and Safranin-O stain (c, j-i) at 4 × magnification (b, c) and 10 × magnification (d-i). Grafted tissue consisted of fibrous tissue in the superficial layer (d) and cartilage-like tissue in the middle to deep layer (e, f) in which the extracellular matrix was stained with Safranin O (c, j-i). Histologically, grafted tissue was well bonded to the subchondral bone (f, i), but the normal layer composition was not observed