Avian and ratite medullary bone

[munyit]

Bird medullary bone is described as a secondary bone tissue that provided calcium for producing eggshell, and have no biomechanical function. Bird medullary tissue is a very brittle and fragile type of bone that the spicules of medullary bone easily separated from the originating layer, but why the thin basal layer remains attached to the cortex? Did it have any mechanical strength or the thin basal layer of medullary bone will eventually completely separated from cortical bone after sometime?