Abstract:
Abstract for Anatomists on the edge meeting, Galway, 27-29 June 2017. Journal of Anatomy Volume 232, Issue 2 S29 Qualitative studies of the calcified tissues in the lumbar vertebral body of the ageing human.
We studied the degree of mineralisation of trabecular and cortical bone and cartilage and thickness of the cortex in lumbar vertebral bodies. We report correlated 3D microscopic imaging methods concerning osteoporotic changes. We examined 34 archival macerated para‐sagittal slices of L4 (17 male, 17 female) by 3D BSE‐SEM and 69 L2 (38 male, 31 female, 70 $pm$ 15 years) obtained through European Union Concerted Action Biomed 1 ‘Assessment of bone quality in osteoporosis’, which were embedded in PMMA: plane block surfaces were carbon coated for quantitative 20 kV backscattered electron scanning electron microscopy (qBSE‐SEM); and later polished and stained with iodine vapour to study uncalcified matrix, providing very high resolution imaging of entire vertical sections. High contrast x‐ray microtomography (48 h per scan) was conducted at 30 μm voxel resolution. Thin sections from block faces were prepared by laser‐ablation for correlative light microscopy. Central compression failure modes encompass calcified end‐plate cartilage and implosion of disc content into the cancellous domain, where cartilage growth and calcification continue. Trabecular and cortical fractures repair with initially low density woven bone, but instigation may involve high density acellular mineralised infill. The anterior cortex, especially, is frequently very thin or absent. In wedge compression and collapse fractures it thickens with inclusion of extra‐bony tissues during drift and collapse. QBSE‐SEM showed 50% of all ‘bone’ to lie in bin 5 of 8 of the normal qBSE‐SEM range (corresponding to 1.99 g/ml peak found density gradient centrifugation): 29.10% in males and 27.44% in females is very highly mineralised (bins 6–8). Much of this is not bone, but calcified cartilage in the end‐plates and Sharpey fibre bone and calcified ligament and fibrous periosteum, which become incorporated into the cortices as they drift outwards and anteriorly: spaces originally outside the cortex become included within the bone organ and develop marrow histology. The abundance of calcified ligament and periosteum should be factored into thinking about failure properties of the anterior cortex. More highly mineralised phases may not be ‘bone’: they will be artefactually represented as ’thicker’ in clinical CT. They have a different ‘grain’ than `bone’ and will have different tendencies to fracture. No ethical approval was required for this study.
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