|3475 Torrance Blvd., Ste F
Torrance, CA 90503
Office hours: M-F, 9am
– 5 pm
Worker’s compensation, Medicare
and most insurance plans accepted.
In September 2008, we will be moving to a beautiful new 4,400 sq ft,
state of the art dedicated hand center located at 2808 Columbia Ave
in Torrance, CA., which will feature onsite nerve conduction studies,
occupational hand therapy and digital x-ray.
CUBITAL TUNNEL SYNDROME
Similar to carpal tunnel syndrome (CTS), this condition is the name given
to a peripheral nerve entrapment. The nerve involved however is the ulnar
nerve, as it passes through a natural tunnel behind the elbow. The ulnar
nerve is responsible for the sensation to the small and ring fingers,
as compared to the median nerve which supplies the thumb, index and middle
fingers. The ulnar nerve supplies all of the small intrinsic hand muscles
which are responsible for approximately 50% of the grip strength. This
region of the ulnar nerve has been commonly referred to as the “funny
bone”, since a blow to this nerve behind the elbow results in an
electric shock like sensation radiating to the small and ring fingers.
When the nerve is compressed, this occurs much more readily with only
minor stimulation of the nerve.
The ulnar nerve (C8-T1) arises from medial cord of the brachial plexus
and passes through the medial intermuscular septum where it enters the
upper inner aspect of the arm. It is then crossed by thick layer of tissue
called “fascia” which runs from this septum to the triceps
muscle 8 cm above the elbow (antebrachial fascia). It then lies on top
of a groove behind the bone prominence on the inside of the elbow (“the
medial epicondyle”) where it is crossed over by fibrous bands (Osborne’s
ligament) which form a roof over the groove. The ulnar nerve then dives
between the two heads of the flexor carpi ulnaris (FCU) which is the large
muscle on the inside of the upper forearm. The aponeurosis or bands of
fascia uniting the heads of the FCU is a common site of ulnar nerve entrapment.
During a nerve decompression all 5 of these sites must be released to
prevent secondary nerve impingement, which will lead to a persistence
The ulnar nerve at the elbow level is composed of 1 large nerve bundle
or fascicle and 2-3 small fascicles. The motor fibers to the flexor carpi
ulnaris, the intrinsic hand muscles and the deep flexors of the small
and ring finger lie deep within the nerve, while the sensory fibers are
superficial. Since the site of compression often starts on the superficial
surface of the nerve, sensory symptoms occur earlier and more commonly
i.e. numbness and tingling of the fingers, versus muscle weakness.
The ulnar nerve glides 6-10 mm and elongates up to 5 mm when the elbow
goes from full extension to full flexion. The condylar groove is round,
spacious in extension and becomes a flattened triangle during flexion
(narrowed by 55%). The pressure within the nerve normally increase 2X
with wrist extension, elbow flexion and shoulder elevation in the normal
situation, but 6 fold if the nerve is tethered.
Nerves normally glide as much as 5-8 cm with elbow flexion and extension.
This allows the nerve to adapt to the difference in length with joint
motion, without compromising the nerve circulation. When there is inflammation,
the nerve becomes tethered. This is akin to placing your finger on the
fret of a guitar string. The shortened segment of the guitar string vibrates
at a higher frequency when plucked. In a similar fashion, if the ulnar
nerve is tethered at the elbow, the remaining shorter sections of the
nerve before and after the site of nerve tethering must overstretch to
accommodate the changes in length between full elbow flexion and full
extension. As a consequence, the blood supply to the nerve is strangled,
which leads to the symptoms of finger tingling and numbness.
An ulnar nerve injury at the elbow that is due to mechanical compression,
or nerve traction due to scarring hence leads to microstretching of the
fixed nerve. Continued trauma results in fixed scar (compression). This
leads to impairment of the normal intraneural circulation which leads
to a “pins and needles” sensation (paresthesiae), of the small
and ring fingers. Initially the compression causes intermittent swelling
within the nerve substance, which in turn causes intermittent symptoms.
With continued pressure, the nerve loses it’s outer insulating cover
(myelin) similar to longstanding carpal tunnel compression. This local
demyelination leads to a loss of sensation in the fingers, as well as
muscle weakness and wasting. If unrelieved the nerve fiber degeneration
causes permanent muscle wasting and a loss of finger sensation, that does
not reverse following surgery.
Some of the inciting events that lead to ulnar nerve compression include
activities that involve repetitive elbow flexion/extension such as assembly
line work or in throwing athletes. A common precipitating event is talking
on a cell phone since the elbow is flexed for long periods of time while
the user holds the phone to their ear. Other causes include direct trauma
to the ulnar nerve, elbow fractures and postoperative palsy from nerve
traction or compression due to limb positioning on the operating table.
The majority of cases however are of an unknown cause or idiopathic.
In mild cases the patient complains of intermittent paresthesiae or tingling
of the small and ring fingers, subjective hand weakness and clumsiness.
In more advanced cases the paresthesias become persistent and the patient
develops muscle atrophy. The diagnosis is based on the appropriate symptoms
as well as a positive elbow flexion test. This is a provocative test that
places the ulnar nerve on maximal stretch by flexing the elbow and extending
the wrist. The reproduction of numbness or tingling in the small and ring
fingers after 1 minute is considered positive. Many patients with carpal
tunnel syndrome will also have signs of cubital tunnel syndrome, since
both syndromes are precipitated by similar activities. A nerve conduction
study is often useful in grading the degree of nerve entrapment. Most
patients however, will have normal nerve conduction studies unless the
nerve compression is longstanding or very advanced.
Conservative Treatment :
Unless there is a sensory and motor loss the initial treatment is always
conservative. This consists mostly of activity modification which focuses
on maintaining the elbow in a more extended position during activities
such as typing or writing. Patients are counseled in avoidance of resting
their head on their hands which leads to direct nerve compression through
leaning on a flexed elbow, resting their forearms on the car window or
prolonged elbow flexion while holding a telephone handset to their ear.
The use of an elbow extension splint at night is encouraged to avoid the
nocturnal symptoms arising from sleeping with a flexed elbow, in addition
to taking NSAIDs. Unlike carpal tunnel syndrome, cortisone injections
are of a limited value, but most patients can safely be treated conservatively
for a longer period of time.
If there is no response to these conservative measures after a reasonable
length of time (2-3 months) surgical decompression may be considered.
There are a number of different techniques for decompressing the nerve,
ranging from releasing the cubital tunnel and leaving the nerve in place
(in situ release), to transposing the nerve in front of the elbow underneath
the skin (subcutaneous transposition) to burying it within (intramuscular)
or underneath the forearm flexor muscles (submuscular transposition).
The most common procedure consists of a subcutaneous anterior nerve transposition,
which involves moving the nerve anterior to the elbow and leaving it just
underneath the subcutaneous tissue (link to ulnar nerve transposition
video). This accomplishes two things. By moving the nerve in front of
the axis of elbow rotation, the nerve is now relaxed rather than stretched
with elbow flexion. In addition, the nerve is moved from a fibrotic compressing
bed, to a healthy uninflammed area. I favor the use of a mini-incision
approach since patients have a more cosmetic scar and less postoperative
pain than with the standard 10-12 cm incision. The procedure is performed
by making a 2-3 cm incision just below the medial epicondyle, which is
the bony prominence on the inside of the elbow. The tough fibrous bands
over the ulnar nerve in the epicondylar groove are released link to cubital
tunnel figures 1- 2). The nerve is also decompressed below the epicondyle
for an additional 5 – 7 cm as it passes in to the forearm between
the two heads of the flexor carpi ulnaris muscle and 8 cm above the epicondyle
by dividing the deep brachial fascia in the upper arm by retracting the
skin and using and endoscopic assist (link to Endoscopic ulnar nerve video).
Next a 1x 1 cm flap of the tough covering over the common flexor muscle
origin or fascia is raised and placed underneath the transposed ulnar
nerve link to cubital tunnel figures 3 -5). This prevents the nerve from
falling back in to the groove or snapping back and forth over the medial
epicondyle, during elbow flexion and extension. The end result is a very
small and cosmetic scar (link to cubital tunnel figures 6- 8). During
an ulnar nerve decompression special attention is pain to 4 separate sites
which must be release to adequately decompress the nerve and to prevent
secondary impingement once it is transposed. This includes the deep brachial
fascia, the medial intermuscular septum, the epicondylar groove and the
fibrous aponeurosis between the two heads of the flexor carpi ulnaris
muscle. Care is take to the include the blood vessels that run with the
ulnar nerve i.e. the superior ulnar collateral artery, to preserve as
much of the ulnar nerve blood supply as possible.
Depending upon the length of compression, the patient may experience immediate
relief of the symptoms v.s. gradual improvement over time. Unlike the
median nerve at the wrist, the ulnar nerve normally has a large proportion
of fibrous tissue to nerve tissue at the elbow. This results in more intraneural
scarring, and hence it is more common to have residual symptoms following
a cubital tunnel release as compared to a carpal tunnel release.
Because of the large forces acting across the elbow a submuscular transposition
is the procedure of choice for throwing athletes such as baseball pitchers.
In other instances, I prefer to reserve this more extensive release for
cases of recurrent symptoms following a prior subcutaneous release or
those with a subluxing ulnar nerve where the nerve snaps back and forth
across the medial elbow condyle with elbow flexion. A submuscular transposition
may also be considered in very thin individuals with little subcutaneous
tissue since the nerve may not have adequate soft tissue padding following
a subcutaneous transposition and may remain quite sensitive. A submuscular
approach requires a release of the common origin of the forearm flexor
muscles from the medial epicondyle (link to streaming ulnar nerve submuscular
video). The ulnar nerve is then placed deep to these muscles, which are
lengthened and repaired ( link to cubital tunnel figures 9 – 11).
With judicious skin retraction this more extensive procedure can also
be performed through a relatively small incision. The elbow is initially
immobilized in 90 degrees of flexion to protect this repair, followed
by progressive elbow extension exercise over a 4-6 week period. Nerve
gliding exercises are instituted immediately to prevent nerve tethering
in its new location.
The results of an ulnar nerve release are not as predictable as those
following a carpal tunnel release. Even patients with normal nerve conduction
studies however can achieve good results with resolution of the paresthesia
or tingling and increased strength. Patients with motor weakness and sensory
loss fare less well although clinical improvement can continue for up
to 1 year following surgery due to remyelination or “rebuilding”
of the insulating layer of the nerve.
Most people can perform one-handed work activity by the 2nd week followed by light duty including clerical work at 6-8 weeks. Heavy manual labor can often be resumed by 8 -12 weeks.