Hypermineralized lamellae below the bone surface: a quantitative microradiographic study

Hypermineralized lamellae similar to interstitial resting lines were identified by microradiography beneath haversian, endocortical, and trabecular resting surfaces in 42 subjects aged 18-96 years. In cross-sectioned osteons, this hypermineralized lamella appeared as a circle showing the same high microdensity as the inner margin of the haversian canal. Bone tissue separating this circle and the margin was more mineralized than the peripheral lamellae of the osteon. In the tibia, 13.7 +/- 0.9% (Mean +/- SE) of Haversian canals exhibited a hypermineralized circle, localized at a distance of 20 +/- 0.4 microns from the canal wall. The scalloped haversian canals, different from osteoclastic resorption cavities, represented 9.9 +/- 0.7% of the haversian canals. There was a significant correlation between both types of haversian canals. Therefore, hypermineralized lamellae can appear at the end of bone apposition, whatever the bone surface. Their high mineral content may secondarily lead to an increased brittleness of the most superficial lamellae and even to their disaggregation.