Ulnar nerve entrapment occurs when the ulnar nerve in the arm becomes compressed or irritated. The ulnar nerve is one of the three main nerves in your arm. It travels from your neck down into your hand, and can be constricted in several places along the way, such as beneath the collarbone or at the wrist. The most common place for compression of the nerve is behind the inside part of the elbow. Ulnar nerve compression at the elbow is called "cubital tunnel syndrome."
Numbness and tingling in the hand and fingers are common symptoms of cubital tunnel syndrome. In most cases, symptoms can be managed with conservative treatments like changes in activities and bracing. If conservative methods do not improve your symptoms, or if the nerve compression is causing muscle weakness or damage in your hand, your doctor may recommend surgery.
At the elbow, the ulnar nerve travels through a tunnel of tissue (the cubital tunnel) that runs under a bump of bone at the inside of your elbow. This bony bump is called the medial epicondyle. The spot where the nerve runs under the medial epicondyle is commonly referred to as the "funny bone." At the funny bone the nerve is close to your skin, and bumping it causes a shock-like feeling.
Beyond the elbow, the ulnar nerve travels under muscles on the inside of your forearm and into your hand on the side of the palm with the little finger. As the nerve enters the hand, it travels through another tunnel (Guyon's canal).
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.
The ulnar nerve gives sensation (feeling) to the little finger and to half of the ring finger on both the palm and back side of the hand.
In many cases of cubital tunnel syndrome, the exact cause is not known. The ulnar nerve is especially vulnerable to compression at the elbow because it must travel through a narrow space with very little soft tissue to protect it.
There are a few surgical procedures that will relieve pressure on the ulnar nerve at the elbow. Your orthopaedic surgeon will talk with you about the option that would be best for you. These procedures are most often done on an outpatient basis.
Cubital tunnel release
In this operation, the ligament "roof" of the cubital tunnel is cut and divided. This increases the size of the tunnel and decreases pressure on the nerve.
After the procedure, the ligament begins to heal and new tissue grows across the division. The new growth heals the ligament, and allows more space for the ulnar nerve to slide through.
Cubital tunnel release tends to work best when the nerve compression is mild or moderate and the nerve does not slide out from behind the bony ridge of the medial epicondyle when the elbow is bent.
Ulnar nerve anterior transposition
In many cases, the nerve is moved from its place behind the medial epicondyle to a new place in front of it. Moving the nerve to the front of the medial epicondyle prevents it from getting caught on the bony ridge and stretching when you bend your elbow. This procedure 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), or within the muscle (intermuscular transposition), or under the muscle (submuscular transposition).
For anterior transposition of the ulnar nerve, an incision is made along the inside of the elbow (pictured) or along the back side of the elbow.
Another option to release the nerve is to remove part of the medial epicondyle. Like ulnar nerve transposition, this technique also prevents the nerve from getting caught on the boney ridge and stretching when your elbow is bent.
Depending on the type of surgery you have, you may need to wear a splint for a few weeks after the operation. A submuscular transposition usually requires a longer time (3 to 6 weeks) in a splint.
Your surgeon may recommend physical therapy exercises to help you regain strength and motion in your arm. He or she will also talk with you about when it will be safe to return to all your normal activities.
The results of surgery are generally good. Each method of surgery has a similar success rate for routine cases of nerve compression. If the nerve is very badly compressed or if there is muscle wasting, the nerve may not be able to return to normal and some symptoms may remain even after the surgery. Nerves recover slowly, and it may take a long time to know how well the nerve will do after surgery.