Stover S M, Pool R R, Martin R B, Morgan J P
Department of Veterinary Anatomy and Cell Biology, School of Veterinary Medicine, University of California, Davis 95616.
J Anat. 1992 Dec;181 ( Pt 3)(Pt 3):455-69.
The dorsal cortex of the equine third metacarpal mid-diaphyseal bone was characterised during growth by the histological and microradiographic examination of specimens from 30 horses ranging in age from 2 months to 8 y. Bone from horses aged less than 6 months was characterised by rapid periosteal apposition of circumferential trabeculae of woven bone that were next connected by radial trabeculae to the parent cortex. Deposition of lamellar bone on the inner trabecular surfaces resulted in rows of primary osteons. Replacement of primary bone occurred only after 4 months of age and preferentially in the woven interstitial bone separating rows of primary osteons formed in the postnatal periosteal cortex. Resorption cavities and incompletely filled secondary osteons characterised bone of 1 and 2-y-old horses. Bone from horses older than 3 y contained several generations of secondary osteons, fewer resorption spaces and incompletely filled osteons, and had a greater portion of circumferentially oriented collagen fibres than bone from younger horses. Bone from horses older than 5 y had large resorption cavities characterised by irregular boundaries. We propose that the process of periosteal bone tissue apposition observed in growing foals be called 'saltatory primary osteonal bone formation' and that this process results in faster cortical expansion and larger total surface area for bone deposition than circumferential lamellar, simple primary osteonal, and plexiform mechanisms of periosteal bone formation. We speculate that bone from 1 and 2-y-old horses would be more susceptible to fatigue microdamage resulting from compressive loads because of high porosity, few completed secondary osteons and low proportion of circumferentially oriented collagen fibres.
通过对30匹年龄从2个月到8岁的马的标本进行组织学和显微放射学检查，对马第三掌骨骨干中部的背侧皮质在生长过程中的特征进行了研究。6个月龄以下马的骨骼特征为，骨膜快速附着编织骨的环行小梁，这些小梁随后通过放射状小梁与母皮质相连。在内部小梁表面沉积板层骨，形成了一排排初级骨单位。初级骨的替代仅在4个月龄后发生，且优先发生在出生后骨膜皮质中形成的一排排初级骨单位之间的编织间质骨中。1岁和2岁马的骨骼特征为吸收腔和未完全填充的次级骨单位。3岁以上马的骨骼含有几代次级骨单位，吸收间隙和未完全填充的骨单位较少，并且与年轻马的骨骼相比，其周向排列的胶原纤维比例更大。5岁以上马的骨骼有边界不规则的大吸收腔。我们提出，在生长中的马驹中观察到的骨膜骨组织附着过程应称为“跳跃式初级骨单位骨形成”，并且与骨膜骨形成的环行板层、简单初级骨单位和丛状机制相比，这一过程导致皮质扩张更快，骨沉积的总表面积更大。我们推测，1岁和2岁马的骨骼由于孔隙率高、完整的次级骨单位少以及周向排列的胶原纤维比例低，因此更容易受到压缩载荷导致的疲劳微损伤。
