Relevant Anatomy

The ulnar nerve is one of the three major nerves supplying function to the hand (the others are the median and radial nerves). It provides sensation to the small finger and the adjacent half of the ring finger. It also controls the majority of muscles in the palm, including those that allow grasping large objects, crossing the fingers, and lateral pinch, as when one turns a key, for example. As the ulnar nerve travels from the upper arm into the forearm, it passes through a narrow channel -- called the cubital tunnel -- consisting of a groove in the bone at the inner aspect of the elbow, bridged by a firm fascia or ligament. This is the area affected when one hits their "funny bone".

Cubital tunnel syndrome (CuTS) is a common form of compressive neuropathy, often referred to as a pinched nerve. CuTS occurs when the surrounding structures exert excessive pressure on the ulnar nerve, causing interference in the normal conduction of signals through the nerve. This may result in symptoms of numbness, tingling, pain, weakness, or clumsiness of the hand. Some patients report pain as high as the arm and shoulder, although other causes must also be considered in those cases. Symptoms may be intermittent early in the disease course, and tend to occur at night and with prolonged flexion of or pressure on the elbow. In some cases, the phenomenon is non-progressive and symptoms may remain unchanged or may even improve over time, but the condition tends to be progressive in many patients, and in severe cases the nerve may undergo irreversible damage from the prolonged compression, resulting in constant numbness and muscle wasting in the hand.

This is a question without a conclusive answer. In most cases, there is no single identifiable cause. Evidence suggests that the condition may be of genetic origin in some cases. Additionally, a number of medical conditions may contribute to thickening of the tissues surrounding the ulnar nerve. Diabetes, hypothyroidism, and rheumatoid arthritis all tend to increase the risk of developing CTS. Certain uses of the elbows may also contribute to the disease, and occupational activities are often reported to cause CuTS. However, little evidence exists to support the frequent claims that occupational uses of the hands actually cause CuTS, although such activities may aggravate symptoms. Injury to the elbow can cause anatomic deformity or scarring leading to nerve tension or compression and CuTS.

A hand specialist can usually make the diagnosis of CuTS at an office visit, based on a medical history and physical examination. Electrodiagnostic studies, often referred to as NCV (nerve conduction velocity) and EMG (electromyography) testing, are usually obtained to confirm the diagnosis, determine the severity of the disease, and exclude other nerve problems. In unclear cases, the diagnosis may be difficult even with these methods.

In general, the treatment options for CuTS include elbow splinting and padding, corticosteroid injections, and cubital tunnel release surgery. Use of a spint or pad to hold the elbow in an extended position can minimize the pressure on the ulnar nerve, and many patients find that such an approach provides satisfactory symptom reduction and reduces nighttime awakening. Corticosteriod injections serve to diminish swelling in the tissues surrounding the cubital tunnel, thereby reducing pressure on the ulnar nerve. Injections can be effective but temporary, lasting only a few weeks to a few months in most cases.

Cubital tunnel release surgery is justified if examination or electrodiagnostic studies indicate severe disease with loss of nerve cells, or if a patient's symptoms are not acceptably relieved by non-surgical treatments. CuTR is a very common surgery, and success rates near 90% are expected when the procedure is performed properly and on the appropriate patients. Relief of pain and nighttime symptoms is usually accomplished. So long as nerve damage is not present preoperatively, return of sensation and strength should occur, although the recovery process may take a year or more to complete. With more severe disease, some degree of permanent numbness and weakness should be expected, but CuTR may still provide worthwhile improvement and should at least halt the disease from causing further damage to nerve function.

The conventional method of CuTR is the in-situ release technique. CuTR is an outpatient surgery, usually performed under general anesthesia, using an incision approximately three to four inches in length along the inner aspect of the elbow. Osborne's ligament and the adjacent fascia are incised, leaving the ulnar nerve unrestrained within the floor of the cubital tunnel. The skin incision is then sutured. Sutures are removed within two weeks. Restrictions on use of the elbow are lifted after the incision has healed, but it may take two to three months for residual soreness to resolve.

A more extensile procedure is anterior ulnar nerve transposition (UNT). This procedure involves the same elements as CuTR, but with UNT the nerve is fully mobilized from its surroundings over several inches at the elbow level, and it is permanently shifted forward out of the cubital tunnel where it is supported by creating a new sling of fasica or muscle. Although UNT was historically the more popular approach, current studies reveal that it is more invasive, but no more effective, than simple CuTR. As such, it is usually only employed for less straighforward secondary cases with a history of prior surgery, trauma, or other anatomical abnormality in the affected area.