Cubital Tunnel Syndrome

Cubital Tunnel Syndrome

Normal Elbow and Forearm Anatomy

The elbow and forearm form a functional unit whose primary role is to accurately position the hand in space. The elbow has a long lever arm and moves the forearm and hand 130 degrees covering much of the functional space used in our activities of daily living and in this sense the elbow is considered the most important single joint of the upper limb, second only to the thumb carpometacarpal joint. The functional space is defined as the space directly in front of a person’s body that lies below eye level and above the belly button. Because the elbow joint covers the entire functional space by virtue of its arc of motion, there has never been a satisfactory position to fuse an elbow joint if it were ever destroyed by injury or disease.

The elbow anatomy is best understood by thinking of it in three layers. The first layer is the bony layer, the second layer is the ligament layer and the third layer is the muscular layer within which the arteries and nerves travel.





Elbow & Forearm Elbow Joint Front View & Side View


The first layer is comprised of three bones that unite to form the elbow joint. The elbow joint is located at the lower end of the arm bone (humerus), and the proximal end (towards the shoulder) of the radius and ulna which are the two forearm bones. These three bones allow the elbow to bend (Flex) and straighten (Extend) in a hinged type motion and the forearm to rotate the hand in a palm up (supination) and palm down position (pronation). The joint surfaces of the elbow are covered by hyaline cartilage which forms a cushioned layer that allows for smooth gliding and painless elbow motion.

Elbow & Forearm Ligament LayerElbow Joint Ligament Layer





Lateral Elbow Ligament View Medial Elbow Ligament View



The second layer in the elbow and forearm is the capsular ligament layer made up of collagen tissue. The ligament layer in the forearm is called the interosseous membrane. The collagen tissue forming the elbow joint capsule is normally very thin except on the inside (medial) and outside (Lateral) sides of the elbow where thickenings in the collagen substance form the ligaments of the elbow. These ligaments provide passive stability to the elbow joint keeping the humerus, radius and ulna together, allowing them to function as a unit.




Foerarm Flexor CompartmentForearm Flexor & Mobile Wad Compartments





Elbow Flexor Muscles Elbow Extensor Muscles



The third layer of the elbow and forearm is the muscle layer and is formed by the various muscle groups that pass through the elbow and forearm either originating (beginning) or ending in the elbow and forearm. The muscles of the arm that pass through the elbow include the triceps muscle in the back of the arm and the brachialis and biceps muscles in the front of the arm. The forearm muscles that cross the elbow joint are divided into three compartments with each compartment containing several muscles that work to move the elbow, forearm, wrist and hand in specific directions. The three compartments are: 1. the extensor compartment 2. the flexor compartment and 3. the mobile wad of Henry compartment. The median, ulnar, and radial nerves pass through the elbow and forearm within the muscle layers and innervate the muscles within these compartments as well as, the muscles of the hand.

Pathology

Cubital tunnel syndrome is the compression of the ulnar nerve at the level of the elbow. The condition has many causes and includes direct trauma to the nerve or by keeping the elbow bent for prolonged periods of time which occurs in many professions requiring the use of computersor simply in individuals accustomed to placing their hand under their chin while their elbow is bent and positioned on top of a table. Other activities that can increase the pressure on the ulnar nerve with bending the elbow is speaking on the phone for prolonged periods of time, with the elbow bent. Certain individuals have the habit of sleeping at nightwith their elbow bent under the side of their head.


When the elbow is bent more than 90 degrees, it is has been experimentally demonstrated that the ulnar nerve’s blood supply is strangulated causing ulnar nerve symptoms to develop. 17% of the population has an ulnar nerve that slips (subluxes) in and out of its groove called the cubital tunnel, when the elbow goes from a straight to a bent position. This subluxation causes mechanical irritation of the nerve over time and is another reason why ulnar nerve symptoms develop. As pressure builds up in the nerve, the ring and small fingers begin to tingle and in time, become progressively numb. The hand grip strength weakens, the forearm experiences cramping and pain on the small finger side of the forearm. Pain is commonly diffuse beginning in the elbow but can also radiate to the arm pit in one direction and to the hand in the other. Cubital tunnel syndrome is often confused with carpal tunnel syndrome because of the popularity carpal tunnel syndrome. Cubital tunnel syndrome can also occur in the presence of carpal tunnel syndrome and is second only to carpal tunnel in occurrence. The frequency with which it accompanies carpal tunnel syndromeis around 25-50% of the time. Sorting out these differences is done by a thorough history, physical exam and the use of an electrical nerve test called an EMG nerve conduction study that evaluates the muscles innervated by the ulnar nerve and the sensory fibers feeding the ulnar nerve distribution.

Treatment

The non-surgical treatment program is based on two ergonomic changes; the proper sleeping posture and correct daytime habits. Therapists teach patients ergonomically correct work habits, help to adjust workstation configuration,recommend adaptive equipment, and provide proper elbow padding to avoid direct pressure on the nerve and to prevent the elbow from bending excessively. This works for most patients but the improvement takes about three months to demonstrate gains. If the measured nerve compression is severe enoughand all non-surgical attempts have failed to resolve the symptoms, or if excessive nerve mobility exists with subluxation on elbow flexion that causes persistent symptoms, then surgery is recommended.


Most patients can surgically be treated with cubital tunnel syndrome with an in situ release of the nerve which requires an incision that is less than one-inch long on the inside of the elbow. Therapy, after surgery is done as a home exercise program taught in the office and beginning one week after surgery. The elbow sutures are removed on the second week after surgery and use of the arm and hand are encouraged immediately after surgery with return to work about 2 weeks postoperatively. Special circumstances like ulnar nerve subluxation with the ulnar nerve slipping in and out of its groove, or a patient who has had a prior failed ulnar nerve surgery are reasons to transfer the nerve from its normal position into a healthy environment surrounded byrich blood supply. This procedure is called an ulnar nerve transposition which has three techniques:

1. subcutaneously (under the skin),
2. intra-muscularly (in the muscle) or
3. submuscular (beneath the first muscle layer of the flexor pronator mass).

All types of ulnar nerve surgeries are performed as an outpatient procedure. After surgery, a light soft dressing is placed over the wound. Patients are encouraged to use the hand right away with no formal restrictions. A therapist is normally consulted for postoperative rehab with aulnar nerve transposition since this is a more extensive operation. An ulnar nerve transposition takes about three months for a patient to feel much better whereas the in situ release, the patient is close to normal within weeks to a month after surgery.