When a peripheral nerve is cut, the axon segments distal to the injury (furthest away from the spinal cord) die off in a process called "Wallerian degeneration." When the nerve is repaired, the axons in the proximal segment (closest to the spinal cord) regrow into the distal, denervated segment. This growth occurs at a rate of about 1 mm per day. This translates roughly to 1 inch per month, or 1 foot per year. Once the axons regrow back into the denervated muscles, the muscles will begin to function again. During the time it takes for the axons to regrow into the muscles, a process that can take many months, or even years, the muscles will be paralyzed and will atrophy.
This is an important point when dealing with peripheral nerve injuries. The healing process almost invariably requires an extensive amount of time to occur. It is important for patients not to lose hope during this time. It is vital that they participate in their exercises, keeping the affected muscles and joints flexible and ready to be used once again when the axons regrow into them. It is not unusual for patients to undergo a lengthy, complex, peripheral nerve reconstruction procedure, only to see no evidence of recovery for a year or more. This can be immensely frustrating for the patient. Unfortunately, there is nothing in medical science currently that can make these axons grow any faster. Perhaps it is best to think of this delay all as part of the healing process, paving the road to getting better!
Columbia University | Columbia University Medical Center
http://www.cumc.columbia.edu/dept/peripheral-nerve/what_pn.html
Non-tramatic causes of nerve damage respond even slower- I have a polyneuropathic condition(toxic reaction to powerful heart meds over a prolonged period is the leading "guess") that has responded at a rate of about an inch per year.
I assume you are doing physio, Electro stimulation and Vit B treatments along with wearing a dropfoot splint. Hang tough it's slow going, have faith. Remember the nerve has to regenerate totally before you start flexation and muscle improvement.
Keep exercising the foot it's important not to atrophy.