Partly regeneration

1: With a mold and the right amount of suction or pulling tension to regrow the skin. The skin can grow so and so many a year. Extra: The ancient Greecs regrew and enenlarged foreskin.
2: Implant artificial bone.
Advanced: Grow the different bones, the joints, tendons, nerve ways and different muscles from ones own cells and implant everything.

A natural method that probably won't work but is interesting.
Constantly tensing the part and trying to stick out and grow the part.
With suction or pulling tension help it might go faster.

I will try and think of more methods.

Extra: combining a method with pixie dust.

By J.K.

Update:
Finding out how to stimulate controlled bone growth
How to grow a muscle, by contraction ? Self contraction, or artificial with a controlled current.
And then you're already there.
It takes a while to grow the skin, bones and muscle but it is possible.

Update:
The use of constant vibrations.

Update:
Studying animal regeneration. Axolotl (can regrow limbs and even parts of their brain)(and they live in water, will they also regenerate on land? They are amphibious), flatworms that can even regenerate their heads, lizard tail regrowth.
Some studies are already being done.
-Look at the cells and finding out more about their DNA and genes that make this possible.