Nyssen-Behets C, Duchesne P Y, Dhem A
Institut d'Anatomie, Université de Mons-Hainaut, Mons, Belgium.
Gerontology. 1997;43(6):316-25. doi: 10.1159/000213871.
Structural modifications are considered to play a significant role in the age-related alterations of bone quality and strength. Senescent compact bone is characterized by an increasing heterogeneity of aspects, including high numbers of lowly mineralized osteons as well as the presence of osteons with hypermineralized lamellae or with a notched haversian canal wall, and of double-zone osteons. These latter three types of osteons are different from the structures involved in the haversian remodeling. In the present study, blocks of midshaft tibia from 7 young men (18-39 years), 14 aged men (50-92 years) and 15 aged women (57-96 years) were embedded in methyl methacrylate in order to perform microradiographic and histomorphometric analysis of undecalcified sections. The intracortical porosity was higher in the aged men than in the young ones, as were the numbers of haversian structures and, to a lesser extent, the diameters of the haversian canals. The aged women showed the same tendency, with cortical porosity still higher than in the men. The osteons with hypermineralized lamellae, those with a notched canal and the double-zone osteons appear to constitute large subgroups of the total haversian population, even in the early adult life. Among them, only the osteons with a notched canal wall increased in frequency with age. The 3 types are much more numerous than the structures involved in the typical haversian remodeling. The correlations between their frequencies as well as their significant topographic association corroborates the hypothesis that the hypermineralized lamellae may crumble down because of their excessive brittleness, giving rise to the haversian canals with notched walls. These enlarged canals could be refilled by bone apposition and result in the double-zone osteons. The 3 types of osteons could constitute different steps of one mechanism of bone desintegration and repair occurring very progressively, which might contribute to modify the bone quality and to increase the intracortical porosity.
结构改变被认为在与年龄相关的骨质量和强度变化中起重要作用。衰老的致密骨的特征是各方面的异质性增加，包括大量矿化程度低的骨单位，以及存在具有过度矿化板层或有缺口的哈弗斯管管壁的骨单位，还有双区骨单位。后三种类型的骨单位不同于参与哈弗斯重塑的结构。在本研究中，将7名年轻男性（18 - 39岁）、14名老年男性（50 - 92岁）和15名老年女性（57 - 96岁）的胫骨中段骨块嵌入甲基丙烯酸甲酯中，以便对未脱钙切片进行显微放射照相和组织形态计量分析。老年男性的皮质内孔隙率高于年轻男性，哈弗斯结构的数量以及哈弗斯管直径在较小程度上也是如此。老年女性表现出相同的趋势，皮质孔隙率仍然高于男性。具有过度矿化板层的骨单位、有缺口管的骨单位和双区骨单位似乎构成了整个哈弗斯群体的大子组，即使在成年早期也是如此。其中，只有有缺口管壁的骨单位频率随年龄增加。这三种类型的骨单位比参与典型哈弗斯重塑的结构要多得多。它们频率之间的相关性以及显著的地形关联证实了这样的假设，即过度矿化的板层可能因其过度脆性而破碎，从而产生有缺口壁的哈弗斯管。这些扩大的管可以通过骨附着重新填充并导致双区骨单位。这三种类型的骨单位可能构成了一个非常渐进发生的骨解体和修复机制的不同步骤，这可能有助于改变骨质量并增加皮质内孔隙率。
