Nerve Healing
Digital nerve lacerations are frequently treated at California Hand Center. Put simply, the two ends of a cut nerve are sewn back together underneath a microscope.

However, the actual healing of a cut nerve is much more complicated. Nerves run from proximal to distal. That is, they originate centrally (in the brain or spine), and radiate outwards (to the fingertips, or wherever else it terminates). When a nerve is cut, it dies from the point of laceration, all the way to its endpoint in the fingertip. To restore sensation to the fingertip, the nerve has to heal/grow from the point of laceration all the way out to the fingertip. The point of repairing the nerve is so that as the nerve grows back out, it has a pathway to follow, out to the fingertip. If a nerve is not repaired, it often can’t find its way back out to the fingertip, and just stops growing, usually where it was cut.

Even after a nerve is surgically repaired, it takes a tremendously long time for it to heal. First, just to jump across the gap of the repair, it typically takes a month or so. Then, it grows out a millimeter per day (or, about an inch per month). Thus, even to restore sensation to the tip of a finger which was cut at its base, may take several months.

Complicating matters, nerves seem to lose their “drive” to heal after several months. In general, the greatest gains in return of sensation come in the first few months after surgery. After about a year, whatever you have, is likely all that you should be able to expect. Anything more is gravy. Thus, if a nerve is cut in the arm, it’s unlikely that sensation/innervation will return to the end organ (i.e. fingertip). Even with a technically-perfect and timely nerve repair, the distance is just too great for the nerve to heal before it runs out of steam and stops growing. Some sensation/function may return, but it won’t likely be complete.