Morphometrical Analysis
Morphometrical parameters are obtained from digital BE-images, light microscopy images of specifically stained or flourescence labelled bone sections. One can distinguish between static and dynamic histomorphometrical parameters. Static morphometric parameters are reflecting the structure and the cellular activity at the time-point of the biopsy while the dynamic parameters give information on amount of bone formation between two given time points.
Typically, structural parameters such as bone volume per tissue volume (BV/TV), trabecular number (Tb.Nb.), trabecular thickness (Tb. Th.) etc. are used to characterize the trabecular features, while cortical width (Ct.Wi.) and porosity are providing information on cortical bone. These parameters can be obtained easily from the digital BE-images.
Specific staining (Giemsa and trichrome Goldner's) of 3 micrometer thick undecalcified microtom sections of bone tissue allows the determination of static parameters of bone formation and resorption.
By computer assisted light microscopy parameters such as osteoid volume (OV/BV), osteoid surface (OS/BS), osteoid thickness (O.Th), osteoblasts surface per bone surface (Ob.S./BS), osteoclast number per bone surface (Oc.N/BS) and eroded surface per bone surface (ES/BS) etc. are measured.
For the determination of the dynamic parameters, the biopsies are usually fluorescence double labelled by intake of tetracycline for 3 days followed by 12 days free followed again by 3 days tetracycline (3/12/3). The bone biopsy (Bx) is then taken 5 days after. Tetracycline is incorporated to the mineralizing areas of the bone and is therefore labelling the newly mineralizing bone sites. Subsequently, the newly formed bone matrix can be identified in the fluorescence light microscope by fluorescent bands. Parameters describing the dynamics of bone formation can be obtained such as mineral apposition rate (MAR) and bone formation rate per bone surface (BFR/BS).