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The periosteum, rich in blood vessels and nerves, is essential for bone growth and regeneration. This sounds like a very difficult thing to transplant or invoke with stem-cells or such, but the idea of being able to grow periostem (sorry for the visual) but like a placenta that one could administer to a graft of sorts, might be an interesting avenue to regrow things...
EDIT - well, hot darn, I was on the correct path:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8858911/
>>>"Using biomimetic methods for artificial periosteum synthesis, membranous tissues with similar function and structure to native periosteum are produced that significantly improve the efficacy of bone grafting and scaffold engineering, and can serve as direct replacements for native periosteum. Many problems involving bone defects can be solved by preparation of idealized periosteum from materials with different properties using various techniques."
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So, yeah - it looks like thats the way forward, its just the "Various Techniques(tm)" that still need refining, I assume...