Ulnar Nerve Entrapment at the Elbow (Cubital Tunnel Syndrome)
The elbow is a complex joint that allows bending and straightening (flexion and extension), and forearm rotation (pronation, palm down; and supination, palm up). The elbow is formed by the joining of three bones: the upper arm (humerus), the forearm on the pinky finger side (ulna), and the forearm on the thumb side (radius). Held together by muscles, ligaments and tendons, the elbow is a combination hinge and pivot joint. The hinge part of the elbow allows the arm bend like the hinge of a door, while the pivot part makes it possible for the lower arm to twist and rotate. There are several muscles, nerves and tendons that cross at the elbow.
One of three main nerves in the arm, the ulnar nerve travels from the neck, through a tunnel of tissue (cubital tunnel) that runs under a bump of bone (medial epicondyle) at the inside of your elbow. The spot where the ulnar nerve runs under the medial epicondyle is commonly referred to as the "funny bone" because here, the nerve is close to the skin and bumping it causes a shock-like feeling.
Beyond the elbow, the ulnar nerve travels under muscles on the inside of the forearm and down into the hand, on the palm side with the little finger. As it enters the hand, the ulnar nerve travels through another tunnel (Guyon's canal). The ulnar nerve enables sensation in the little finger and half of the ring finger. It also controls most of the small hand muscles that help produce fine movements, as well as some of the larger muscles in the forearm used to form a strong grip.
Ulnar nerve entrapment at the elbow, or cubital tunnel syndrome, occurs when the ulnar nerve in the arm becomes compressed or irritated. Although there are various areas where the ulnar nerve can become constricted, such as at the collarbone or wrist, it occurs most commonly behind the inside of the elbow.
Most symptoms occur in the hand, but cubital tunnel syndrome can also cause an aching pain on the inside of the elbow.
- Numbness, tingling, or the sensation of "falling asleep" (paresthesia)—These symptoms may come and go, commonly occurring in the ring finger and little finger, especially when the elbow is bent, such as when driving or holding a phone. In some cases, it may be difficult to move the fingers in and out, or to manipulate objects. Numbness in the fingers may even disturb sleep during the night.
- Weakening of the grip and difficulty with finger coordination—Typically occurring in more severe cases of nerve compression, these symptoms may interfere with activities that require manual dexterity, such as typing or playing an instrument.
- Muscle wasting—This may occur if the nerve is extremely compressed or has been compressed for a long period of time. Once muscle wasting occurs, it cannot be reversed. For this reason, it is critically important to see your physician or orthopaedic surgeon immediately if symptoms are severe, or if they are not severe but have been present for more than 6 weeks.
Although there are several things that can put pressure on the nerve at the elbow, in many cases, the exact cause of cubital tunnel syndrome is not known.
- Repeated or prolonged bending of the elbow—When bending the elbow, the ulnar nerve must stretch around the boney ridge of the medial epicondyle. Because this stretching can irritate the nerve, repeatedly bending the elbow or keeping the elbow bent for long periods of time, even during sleep, can cause painful symptoms.
- Ulnar nerve slides back and forth—In some people, the nerve slides out from behind the medial epicondyle when the elbow is bent. Over time, this may irritate the nerve.
- Prolonged leaning on the elbow—Leaning on the elbow for long periods of time can put pressure on the nerve.
- Fluid buildup in the elbow—A buildup of fluid in the joint, such as that occurring with elbow bursitis, can cause swelling that may compress the ulnar nerve.
- A direct blow to the inside of the elbow—Commonly referred to as "hitting your funny bone," this can cause pain, an electric shock-like sensation, and numbness in the little and ring fingers.
Factors that increase the risk of developing cubital tunnel syndrome include: prior fracture or dislocations of the elbow, bone spurs or arthritis of the elbow, swelling of the elbow joint, cysts near the elbow joint, and activities that require repetitive or prolonged bending or flexing of the elbow.
After discussing your symptoms, medical history, medications and activities, your physician will examine the arm and hand.
- Physician examination—In order to determine if there is compression of the nerve, and if so, which nerve and the exact location of the compression, your doctor may perform a variety of specific tests, such as: tapping over the nerve at the funny bone to cause a shock-like sensation in the ring and little fingers (this can also occur when the nerve is normal); bending the elbow to see if the ulnar nerve is sliding out of the normal positon; moving the neck, shoulder, elbow and wrist in certain ways to determine if different positions cause symptoms; checking for feeling and strength in the hand and fingers, which can reveal compression of the ulnar nerve in the elbow.
- X-rays—Although most causes of ulnar nerve compression cannot be seen on an X-ray, your physician may recommend these imaging tests of the elbow or wrist to look for bone spurs, arthritis or other places where the bone may be compressing the nerve.
- Nerve conduction studies—Like electrical cables, nerves travel through the body carrying messages between the brain and muscles. If a nerve is not working well, this communication takes too long. During this test, small needles are inserted into some of the muscles controlled by the ulnar nerve. By stimulating the nerve in various places and measuring the length of time needed for each response, your physician can determine if and where the nerve is compressed, and if the compression is severe and causing damage to the muscle.
If the nerve compression has not caused a great deal of muscle wasting, the orthopaedic surgeon will most likely begin treatment with nonsurgical options. In most cases, symptoms can be managed with conservative treatments such as bracing and changes to daily activities. If these methods do not improve symptoms, or if the nerve compression is causing muscle weakness or damage in the hand, surgery may be recommended.
- Home remedies—There are many things you can do at home to help relieve symptoms, but if symptoms interfere with normal activities or last more than a few weeks, be sure to schedule an appointment with your physician. The following can be effective options: avoiding activities that require the arm to remain bent for long periods of time; during frequent computer use, making sure the chair is not too low and not resting elbows on the armrest; not leaning on the elbow or putting pressure on the inside of the arm (such as driving with the arm resting on the open window); keeping the elbow straight during sleep by wearing an elbow pad backwards at night, or wrapping a towel around the straightened elbow before bed to prevent bending.
- Nonsteroidal anti-inflammatory medication (NSAIDs)—If you have just begun to experience symptoms, your physician may recommend anti-inflammatory drugs, such as ibuprofen or naproxen, to help reduce swelling around the nerve. Most people are familiar with nonprescription NSAIDs, such as aspirin and ibuprofen, for relieving pain, inflammation and swelling. However, whether using over-the-counter or prescription strength, these drugs must be taken carefully. Using these medications for more than one month should be reviewed with your primary care physician. If you develop acid reflux or stomach pains while taking an anti-inflammatory, be sure to talk to your doctor. Although steroids, such as cortisone, are powerful anti-inflammatories, steroid injections are generally not used for cubital tunnel syndrome due to risk of damage to the nerve.
- Bracing or splinting—Your doctor may prescribe a padded brace or splint to be worn at night to keep the elbow in a straight position during sleep.
- Nerve gliding exercise—In an effort to improve symptoms, some physicians recommend special exercises to help the ulnar nerve slide through the cubital tunnel at the elbow and the Guyon's canal at the wrist. These exercises may also help prevent stiffness in the arm and wrist.
If nonsurgical methods have not improved your condition, the ulnar nerve is very compressed, or the nerve compression has caused muscle weakness or damage, your orthopaedic surgeon may recommend surgery to relieve pressure on the ulnar nerve at the elbow. These procedures are often done on an outpatient basis. Your orthopaedic surgeon will discuss the options with you and determine which is best for you.
- Cubital tunnel release—The ligament "roof" of the cubital tunnel is cut and divided in order to increase tunnel size and decrease pressure on the nerve. As the ligament begins to heal, new tissue growth allows more space for the ulnar nerve to slide through. This procedure tends to work best when 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—The ulnar nerve is moved from its position behind the medial epicondyle to in front of it, to prevent it from getting caught on the bony ridge and stretching when bending the elbow. The nerve can be moved to one of the following: 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).
- Medial epicondylectomy—The ulnar nerve is released by removing 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.
- Risks and complications—With any surgery, there are some risks, and these vary from person to person. Complications are typically minor, treatable and unlikely to affect your final outcome. Your orthopaedic surgeon will speak to you prior to surgery to explain any potential risks and complications that may be associated with your procedure.
Depending on the type of procedure you have, it may be necessary to wear a splint for a few weeks following surgery. Typically, submuscular transpositions require splint use for a longer time (3-6 weeks). Physical therapy exercises may be recommended to help you regain strength and motion in your arm. Your orthopaedic surgeon will determine when it is safe for you to return to your normal activities.
The results of surgery for cubital tunnel syndrome 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 after surgery and some symptoms may remain. Nerves recover slowly, however, so a long period of time may be needed to know how much the nerve has improved.