Fig. 6.

Histologic evaluation of bone healing at 28 and 56 days post-operatively. Representative longitudinal H&E stained sections (2× magnification) of the femora in group I (a, h), group II (b, i), group III (c, j), group IV (d, k) and group V (e, l) demonstrate new periosteal and endosteal bone formation adjacent to the host cortical bone with bridging of the defect. The newly formed cortex is significantly thinner in BMP-2 alone groups (groups I and IV) compared to groups treated with a combination of BMP-2 and OPG (groups II, III and V). In groups VI (f, m) and VII (g, n), fibrous and adipose tissues are evident within the defect, with minimal bone formation at the proximal and distal ends.