CUBITAL
TUNNEL SYNDROME
Cubital tunnel syndrome is the
most common peripheral nerve compression syndrome after carpal tunnel syndrome
and involves compression of the ulnar nerve at or around the elbow. The cubital
tunnel is a fascial sheath that the ulnar nerve runs through just posterior to
the medial epicondyle. Nerve compression can occur through the tunnel or at
sites just proximal or distal to it, such as the medial intermuscular septum,
the arcade of Struthers, the flexor carpi ulnaris fascia, and the deep
flexor-pronator aponeurosis. A subluxating ulnar nerve may also produce
symptoms similar to those of nerve compression. Other causes of ulnar nerve
symptoms around the elbow can include adhesions from prior surgery; presence of
an anomalous muscle (anconeus epitrochlearis); tumors; snapping of the medial
triceps; bony changes from arthritis, prior fractures, or heterotopic bone; and
anatomic deformities, such as cubitus valgus and cubitus varus. The arcade of
Struthers is an aponeurotic band located approximately 8 cm proximal to the
medial epicondyle that runs from the medial head of the triceps to the medial
intermuscular septum. As the ulnar nerve crosses from the anterior to the
posterior compartment in the distal part of the upper arm, it can pass
underneath this band, if present. The arcade can particularly become a point of
entrapment if the ulnar nerve is transposed anteriorly and the band is not
released.
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| CUBITAL TUNNEL SYNDROME: SITES OF COMPRESSION |
Symptoms of cubital tunnel
syndrome include medial-sided elbow pain and paresthesias in the ulnar side of
the palm and ulnar one and a half digits of the hand. A positive Tinel sign
will re-create these paresthesias by tapping along the course of the ulnar
nerve on the medial side of the elbow. The location of the Tinel sign may help
to localize the exact site of nerve compression. Direct pressure can exacerbate
symptoms by increasing compression of the nerve in the cubital tunnel, whereas
elbow flexion can cause traction-related deformation of the nerve that
increases symptoms. Elbow flexion can also demonstrate evidence of nerve
instability, because the ulnar nerve will typically dislocate or subluxate
anterior to the medial epicondyle with elbow flexion and cause a snapping or
clicking sensation. Snapping of the medial triceps can also create a clicking
sensation at the elbow with range of motion and must be distinguished. With
more chronic or severe cases of entrapment, motor findings can be present,
including weakness and wasting of the intrinsic muscles of the hand. When
symptoms of cubital tunnel syndrome are present, an electromyographic study of
the extremity can be performed both to confirm that the abnormality is
localized to the elbow and to determine the severity of the neuropathy. Ulnar
nerve compression can occur proximally at the cervical spine or brachial
plexus, as well as distally in the forearm, wrist, or hand, although much less
commonly.
Nonoperative management is the
initial treatment in milder cases of cubital tunnel syndrome and consists of
activity modification and splinting to take pressure off the nerve, such as
avoidance of repetitive or prolonged elbow flexion and use of splints that keep
the elbow in a relatively extended position, particularly at night. Elbow pads
can also be worn during the day to prevent compression on the nerve. Surgery is
indicated when nonoperative measures fail and involves in-situ decompression
of the ulnar nerve or ulnar nerve transposition. In-situ decompression is often
used in milder cases, whereas transposition is performed in severe cases and in
situations in which nerve instability is present. When performing an ulnar
nerve transposition, all possible sites of nerve entrapment proximal and
distal to the cubital tunnel should be decompressed, in addition to releasing
the cubital tunnel. This includes release of the arcade of Struthers if
present, excision of the medial intermuscular septum, and release of the flexor
carpi ulnaris and flexor digitorum superficialis fascia. Ulnar nerve
transposition can be subcutaneous or submuscular and acts to decompress the
nerve by placing it in a position anterior to the medial epicondyle.
Subcutaneous transposition is more commonly performed, and in this technique
the nerve is stabilized anteriorly by a loose fasciodermal sling. Submuscular
transposition is considered in cases of revision surgery and in patients with
little to no subcutaneous fat. The flexor-pronator origin is detached with this
technique to allow placement of the ulnar nerve anteriorly and adjacent to the
median nerve. The flexor-pronat r origin is then repaired over the transposed
nerve.
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| Submuscular transposition of ulnar nerve |
