Ultrastructure of Cement Lines

Abstract

Bone remodeling is achieved through the resorptive activity of osteoclasts and the synthetic activity of osteoblast and it continues throughout life. Cement lines are formed by osteoblasts and are recognized between old and new bone. However, the detailed structure of cement lines has still not been clarified. The present study researched the ultrastructure of cement lines in a ferret femur using light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). On LM, many resorption tunnels were recognized in cortical bones. Some osteoclasts in Howship's lacunae were observed at the top of the resorption tunnel (cutting cone), and osteoblasts forming some layers were recognized behind osteoclasts (filling cone). The layer of osteoid was observed under osteoblasts, and it was slightly eosinophilic on the decalcified specimen. A very thin layer of cement lines was recognized between osteoid and old bone, and it was slightly basophilic on hematoxylin and eosin (HE). On the non-decalcified sections stained with toluidine blue (TB), cement lines showed anochromasia in the non-etched specimen, but stained with TB in the etched one. On TEM, cement lines were recognized between osteoid and old bone, and they were revealed as extracellular matrices of an afibrillar layer, with a thickness of about 2µm. On BSE analysis, cement lines of osteon were observed as 1-2µm white lines. Conclusively, the present study indicated that cement lines are extracellular matrices of hypercalcified afibrillar layer having 2µm thickness.

Disturbance of osteonal bone remodeling and high tensile stresses on the lateral cortex in atypical femoral fracture after long-term treatment with Risedronate and Alfacalcidol for osteoporosis

“…On both periosteal and endocortical surfaces thickening of bone was radiologically observed in the transverse radiolucent linear zone. A border between the original lateral cortex and the newly formed endosteal lamellar bone may be a type of the “cement line”, but it is primarily a term for formation of secondary osteon ( Skedros et al, 2005 ; Okada et al, 2013 ). It seems, in this case, endosteal lamellar bone formation is modeling-based formation, started with resorption of the lateral cortex, but not remodeling-based formation ( Fig.…”

The micro and ultrastructural anatomy of bone spicules found in the osteochondral junction of bovine patellae with early joint degeneration

“…That there should be a gap in the spicule–ZCC interface, a result of the removal of the mineral phase from decalcification, requires further discussion in the context of the cement line of secondary osteons. In the latter, studies have shown that the cement line is a hypermineralised zone and collagen deficient (Okada et al, 2013; Hosseini et al, 1999; Skedros et al, 2005), with significantly higher Ca/P molar ratios than bone (Schaffler et al, 1987). Thus with the removal of this mineral phase, a void would result, and this is consistent with previous SEM studies of bone tissue where the cement line and lamellae boundaries were enhanced following citric acid exposure (Congiu & Pazzaglia, 2011) or the collagen fibrils exposed following complete demineralisation with HCL acid (Traini et al, 2005).…”