Split toe nail recovery after surgery

Question
Dear Dr. Huang,
3 weeks ago my 125 pound dog split his back nail.
My vet told me he had to cut the nail back very deep.
My dog is on a strong dose of antibiotics since he has not healed yet.  (he is also wearing an e-collar around the clock)
(He has been back to the vet weekly since his surgery from lack of healing)
Last week my vet looked at his paw and changed his anti-biotic and told me that he will do a culture if it still does not heal.
Today I noticed his nail is coming in from the underneath of the quick of his toe?
Instead of the nail coming in from the top and surrounding the quick and protecting it. (the quick is exposed and thus not protected by a nail nor is it healing.)  Is this possible for the nail bed to be damage and the nail to be coming in from the bottom instead of the top?  Please help,

Answer
It is possible for the nail bed of a toe to be damaged so that the nail comes in as a malformed shape.  Completely underneath I have not seen before, however I could not rule it out.

I would suggest having the culture done to rule out a fungal problem, and your veterinarian can examine the nail as it is presently coming in.

My hugest of apologies for the delayed response as a family emergency kept me unavailable for several days.