There has been recently a number of companies which have started internal lengthening procedures. The advantage is that you don't have pins through the skin and exposed to the air.
Originally invented in England, it was used for tumors where previously the leg would have had to be amputated
http://www.bjj.boneandjoint.org.uk/content/88-B/5/649.long
I contacted the author's of the article in 2003 when my daughter was born to see if the technology could be adapted to PFFD. It makes sense as it would just be the same thing but attached to a rod instead of replacing the bone. The lead doctor said it was not currently designed for PFFD - the device actually replaced the bone - instead of attaching to it. But they were working on a second model that might be feasible.
This system has now made it to the US as the "Precise" system (http://medgadget.com/2011/08/precise-remote-controlled-leg-limb-lengthen...) and has begun to be tested on kids wth PFFD
There is an animation video of it here http://www.youtube.com/watch?v=5qXu8UDtoYY (no blood)
Update:
More information on the Precice internal limb lengthening system was sent in by Lee
http://www.lifebridgeblogs.org/2012/02/13/sinai-surgeons-codevelop-remot...
http://www.newschannel5.com/story/19053747/remote-controlled-leg-lengthe...