See quote above, calcium with vitamin D and vitamins dusted on its food. The bones will harden back up over time but there is no cure for MBD. You will also want to leave a bottle cap in its enclosure with calcium in it, in case the leo wants to lick additional calcium.
Looks a bit dark to be a Tremper (probably resulted from low incubation temps), but I'm still going with that guess along with everyone else.
And I agree with everyone else on another issue; that gecko definitely has Metabolic Bone Disease, caused by low calcium/vitamin levels. Only a vet can truly cure it, but you're going to surely want to make sure that that gecko is getting proper supplementation. I'd dust food daily and leave a dish w/ calcium powder in the tank.