- the selection of follicles which have already started to miniaturize
- damage and trauma inflicted by surgical instruments (e.g. pulling, tucking, and inadvertent severance by the punch edge)
- desiccation due to air drying
- higher than ideal storage temperatures
- being outside the body for too long
- failure of new blood vessels to form around the hair follicles
What Causes Poor Growth After Hair Restoration
Once follicles die, they do not regenerate. Therefore, patients who continue to show signs of baldness and thinning at over 10 months after their hair transplant will need additional surgery to fill in these areas.
Patients who have experienced poor growth after a previous transplant may want to consider a UGraft hair transplant repair:

Body hair transplant for patients with inadequate head donor in the annals of plasic surgery Journal
