http://www.nemours.org/
This hospital is the premier center for people with dwarfism. The head orthopedic Doctor there is the Director for the medical advisory board for Little People of America (LPA). If you have watched any shows on dwarfism (mostly on TLC) then you have probably seen the Doctors at this Hospital. Almost all of these shows feature this hospital at some point.
Eric
PS - If you want to get really technical then the Doctors that know the most about CHH are in Finland. However, most forms of CHH in Finland are exactly the same so unless you have that exact form you would probably not benefit from seeing them. When I say form I mean, variation. The symptoms from CHH can vary greatly from case to case. I'm not quite sure of anyone really knows why at this point. Possibly different parts of the RMRP gene are mutated?