Histologic examination of the ossification front. Section of the control ligamentum flavum (a) showing a thin ossification front and regular arrangement of fiber bundles. In OLF samples (representative case of fused type), note the expanding ossification front, gathering many chondrocytes, and featuring an irregular of calcification front (b). In addition to the ossification front, note the presence of osteoblasts as well as small blood cells with mesenchymal cells (c, d). In the EVG image, elastic fibers exhibit a regular arrangement (e), whereas the OLF samples contained irregular, fragmented fibers or no elastic fibers (f). (a-d) H&E; (e, f) EVG staining. CCA, calcified cartilage area; EVG, Elastica van Gieson; FA, fiber area; FCA, fibrocartilage area; OA, ossified area; OLF, ossification of the ligamentum flavum. Scale bar = 100 μm.
Uchida et al. Arthritis Research & Therapy 2011 13:R144 doi:10.1186/ar3458