The Restrictions on Bone Growth after Puberty are mechanical not chemical

The growth plate phenomenon which purports that growth is no longer possible after puberty only restricts chemical(HGH) not mechanical(limb lengthening surgery) growth. You can send an infinite number of signals to grow bone but if the mechanical tools are not there then no growth will be possible.

The mechanical tools to influence bone are:

1) Impact(tapping something against the bone or jumping)
2) Strain(pulling apart the bone)
3) Compression
4) Torsion, Spiral, twisting, etc.

We have to perform these forces strong enough to create the mechanical space to build the bone(via microfractures) but not strong enough so as to denature the bone(say a multiple compound fracture).

Endochondral ossification merely means that the epiphyseal cartilage cells stop duplicating and where growth once occurred is now what is referred to as a growth plate. This growth plate in no way inhibits growth, it merely means that natural growth is done.

The same process of endochondral ossification which is used to grow the long bones is the same that is used to heal fractures.  Microfractures are smaller fractures but that don't create quite the same microenvironment for cartilagenous growth as larger fractures.

The key is merely finding the best exercises to cause microfractures.  And make sure that other stimuli is added to produce a similar microenvironment as larger fractures or that the fracture is large enough to produce a similar microenvironment.

Mechanical Regulation of Skeletal Development.

"Spatially organized differentiation is vital to the production of functionally appropriate tissues contributing to precise, region specific morphologies, for example transient chondrogenesis of long bone skeletal rudiments, which prefigures osteogenic replacement of the cartilage template, compared with the production of permanent cartilage at the sites of articulation."

"mechanical forces generated by embryonic muscle contractions are required for normal skeletogenesis."

"marking of cells that express Matrilin 1 (within the rudiments) shows that they do not contribute to articular cartilage"

"mature articular cartilage cells can be induced to undergo chondrogenic maturation and hypertrophy by treatment with 5-azacytidine"

"Hydrostatic Pressure (HP) has been largely associated with chondrogenic differentiation whereas tensile strain and fluid induced shear stress are generally shown to induce osteogenesis"