Harvesting method. To provide a standardized evaluation process and locate the area of interest, an appropriate harvesting method was designed: Using a custom-made screw the original direction of the needle could be established (a). A custom-made holder allowed fixation of the bone to a drill press table aligning the original needle path with the axis of a diamond-coated water-cooled core drill (b). The black arrow marks the pin pointer used for defining the drill axis. After screw and pin pointer removal, the core drill was mounted on the drill press and a 32 mm diameter bone cylinder was cut (c). The black line in Figure c marks the cutting mark for histology sections with original needle insertion point and needle path in the center.