How often does conservative treatment of a sesamoid fracture lead to full recovery? enough to participate in athletics, distance running, etc?

They might heal: Vascularity of sesamoid bones are relatively poor. If the fracture is non-displaced then there is a decent chance that the sesamoid bone will heal. If the fracture does not heal and becomes painful or part of the bone dies then it really should be taken out surgically. It's difficult to determine how often these fractures heal via conservative treatment because it depends on the individual's body.

Open Sesame!: Before arriving at the diagnosis of a fractured sesamoid, it is always wise to x-ray the other foot and examine the sesamoids there. These little sesame shapped bones can be in two, three and even more pieces, normally. Having said that, the earlier treatment begins as well as the less weight bearing, the better the chances of a heal. The chances of resolution are so so but not great.