There are a few reasons. By fail, I assume you mean poor or no growth. Poor graft handling, grafts can be squashed and die. Grafts dying of dehydration. Out of the body too long without hydration. Infection caught. Necrosis scarring. Not following post op instructions. Doing these too soon after your hair transplant. Out in the Sun and getting burnt, swimming, strenuous exercise as a few examples. There are a few patients who for an unknown reason the transplanted grafts fail. It is referred to as the X factor. Like all types of transplants, the body can reject them.
When the grafts are extracted they need to be stored in a solution such as HypoThermosol. This prevents then from drying out and keeps them alive. Imagine digging a plant out to move to another location. If it is left out for hours without any water before replanting it will probably die or have stunted growth. Grafts can dry out fairly quickly. Blood supply is another possible cause. Yes, there are bad transplants and failed transplants. Sometimes they may be intertwined.
Interested in the exercise side of things. I'm on day five after my op and I'm following the all the instructions as prescribed on all counts. The info I got from the hair Dr said no exercise for two weeks and then only light exercise for a further two weeks. At the moment I feel pretty good, but it's pretty obvious I shouldn't be dong anything strenuous. Not really sure whats the right level for 2 to 4 weeks and beyond?
Yeah I’ve wondered that. I don’t do any exercise other than walking anyway, but someone like my wife is always in the gym so if I was like her what would be considered light exercise. Also how does exercising effect the HT I can understand sweating etc but how else?