Bone becomes more fragile with ageing. Among many structural changes, a thin layer of highly mineralized and brittle tissue covers part of the external surface of the thin femoral neck cortex in older people and has been proposed to increase hip fragility. However, there have been very limited reports on this hypermineralized tissue in the femoral neck, especially on its ultrastructure. Such information is critical to understanding both the mineralization process and its contributions to hip fracture. Here, we use multiple advanced techniques to characterize the ultrastructure of the hypermineralized tissue in the neck across various length scales. Synchrotron radiation micro-CT found larger but less densely distributed cellular lacunae in hypermineralized tissue than in lamellar bone. When examined under FIB-SEM, the hypermineralized tissue was mainly composed of mineral globules with sizes varying from submicron to a few microns. Nano-sized channels were present within the mineral globules and oriented with the surrounding organic matrix. Transmission electron microscopy showed the apatite inside globules were poorly crystalline, while those at the boundaries between the globules had well-defined lattice structure with crystallinity similar to the apatite mineral in lamellar bone. No preferred mineral orientation was observed both inside each globule and at the boundaries. Collectively, we conclude based on these new observations that the hypermineralized tissue is non-lamellar and has less organized mineral, which may contribute to the high brittleness of the tissue.

随着年龄的增长，骨骼变得更加脆弱。在许多结构变化中，一层薄薄的高度矿化且易碎的组织覆盖了老年人薄股骨颈皮质的部分外表面，并已被提议增加髋部脆性。然而，关于股骨颈中这种超矿化组织的报道非常有限，尤其是其超微结构。这些信息对于理解矿化过程及其对髋部骨折的影响至关重要。在这里，我们使用多种先进技术来表征不同长度尺度的颈部超矿化组织的超微结构。同步辐射微 CT 在高矿化组织中发现比在板层骨中更大但分布较不密集的细胞腔隙。在 FIB-SEM 下检查时，超矿化组织主要由大小从亚微米到几微米不等的矿物质球组成。纳米尺寸的通道存在于矿物球内并与周围的有机基质定向。透射电镜显示球体内部的磷灰石结晶性较差，球体边界处的磷灰石晶格结构清晰，结晶度与层状骨中的磷灰石矿物相似。在每个球体内部和边界处均未观察到优选的矿物取向。总的来说，我们基于这些新观察得出结论，超矿化组织是非层状的，并且具有较少有组织的矿物质，这可能导致组织的高度脆性。纳米尺寸的通道存在于矿物球内并与周围的有机基质定向。透射电镜显示球体内部的磷灰石结晶性较差，球体边界处的磷灰石晶格结构清晰，结晶度与层状骨中的磷灰石矿物相似。在每个球体内部和边界处均未观察到优选的矿物取向。总的来说，我们基于这些新观察得出结论，超矿化组织是非层状的，并且具有较少有组织的矿物质，这可能导致组织的高度脆性。纳米尺寸的通道存在于矿物球内并与周围的有机基质定向。透射电镜显示球体内部的磷灰石结晶性较差，球体边界处的磷灰石晶格结构清晰，结晶度与层状骨中的磷灰石矿物相似。在每个球体内部和边界处均未观察到优选的矿物取向。总的来说，我们基于这些新观察得出结论，超矿化组织是非层状的，并且具有较少有组织的矿物质，这可能导致组织的高度脆性。而在球体边界处的那些具有明确的晶格结构，其结晶度类似于层状骨中的磷灰石矿物。在每个球体内部和边界处均未观察到优选的矿物取向。总的来说，我们基于这些新观察得出结论，超矿化组织是非层状的，并且具有较少有组织的矿物质，这可能导致组织的高度脆性。而在球体边界处的那些具有明确的晶格结构，其结晶度类似于层状骨中的磷灰石矿物。在每个球体内部和边界处均未观察到优选的矿物取向。总的来说，我们基于这些新观察得出结论，超矿化组织是非层状的，并且具有较少有组织的矿物质，这可能导致组织的高度脆性。