The ulnar nerve gives feeling to the little finger and half of the ring finger. It also controls most of the little muscles in the hand that help with fine movements, and some of the bigger muscles in the forearm that help you make a strong grip. This nerve travels from your neck down into your hand, and can be constricted in several places along the way (ulnar nerve entrapment). Depending on where it occurs, the pressure can cause numbness or pain in your elbow, hand, wrist, or fingers. Sometimes the ulnar nerve gets compressed at the wrist, beneath the collarbone, or as it comes out of the spinal cord in the neck. But it is most commonly compressed behind the elbow, where entrapment can cause the fingers to "fall asleep", especially when the elbow is bent.
Ulnar nerve compression at the elbow is called "cubital tunnel syndrome." At the elbow, the nerve travels through a tunnel of tissue (the cubital tunnel) that runs under a bump of bone called the medial epicondyle at the inside of your elbow. The nerve is especially vulnerable at this spot because it must travel through a narrow space close to the skin with very little soft tissue to protect it.
A doctor may recommend surgery for cubital tunnel syndrome if 1) nonsurgical methods do not improve the condition, 2) the nerve is very compressed, or 3) nerve compression has caused muscle wasting. The most common surgical option is moving the nerve from its place behind the medial epicondyle to a new place in front of it, preventing the nerve from getting caught on the bony ridge and stretching when you bend your elbow. This is called an anterior transposition of the ulnar nerve. The nerve can be moved to lie under the skin and fat but on top of the muscle (subcutaneous transposition), within the muscle (intermuscular transposition), or under the muscle (submuscular transposition). The procedure is performed under general anesthesia or with regional anesthetic. A splint may be necessary for a few weeks after the operation.