Figure 7: Histological grading of heterotopic bone formation in HA/TCP implants containing R-cells, L-cells, or vehicle (v) only. The following semiquantitative scale was used: (0) no signs of bone formation (not shown); (1) (panel a) poor bone formation restricted to a single small bone trabeculae (arrow); (2) (panel b) weak bone formation (arrows); (3) (panel c) moderate bone formation occupying less than one half of the section; and (4) (panel d) abundant bone formation, bone spreading over more than one half of the histological section [11]. Four micra paraffin-embedded sections stained by H&E. Scale bar = 500 μm.