Why are my fingernails growing very slowly after hand surgery?

Nail growth. Fingernails growth is not uniform. Longer fingers with longer phalanges grow faster. Some state that nails grow fster in the summer. Nutritional and metabolic issues affects nail growth. Recent trauma or surgery may slow down growth.
Vascular flow. After surgery of the hand the general flow of blood to the hand can be altered to affect the fingernail growth. This is usually not a lomg term issue unless it is a replant part.
Not uncommon. Changes in the rate of fingernail growth after surgery both slower and faster are not uncommon. In time the rate of growth generally normalizes.