Ulnar nerve entrapment at the elbow, the cubital tunnel syndrome, is
increasingly recognized as a source of upper-extremity sensory and motor
symptoms. When nonoperative methods fail to relieve these symptoms and
neurosensory and motor tests document progressive ulnar nerve dysfunction or a
degree of nerve compression resulting in axonal loss, then surgical
decompression of the ulnar nerve is indicated. Anterior submuscular
transposition with use of the musculofascial (z-lengthening) technique is an
approach that decreases pressure on the ulnar nerve throughout the range of
elbow motion.
A 6 to 8-cm incision is made in line with the posterior condylar groove of
the humerus under tourniquet control (Fig.
1). With loupe magnification, the dissection is carried to the
level of the medial humeral epicondyle while the surgeon looks for the
posterior branch(es) of the medial antebrachial cutaneous nerve. The more
distal branch(es) should be kept in the flap, while, for the more proximal
branch(es), the dissection should proceed so that they come to lie
posteriorly. The cubital tunnel is then opened, and the ulnar nerve is
identified (Fig. 2). If there
is an anomalous muscle (the epitrochlearis anconeus), it should be divided.
The proximal neurolysis of the ulnar nerve is completed by incising the fascia
from the medial head of the triceps to the medial intermuscular septum. If
there is an anomalous portion of the medial head of the triceps superficial to
the nerve, this muscle should be divided. A 4-cm length of the medial
intermuscular septum is excised just proximal to the medial humeral epicondyle
(Fig. 3). Often, there are
vessels to cauterize within or subadjacent to this septum. The distal
neurolysis of the ulnar nerve is completed next by opening the rest of the
cubital tunnel, a step that includes division of the band between the two
heads of the flexor carpi ulnaris and continuing distally to divide the fascia
of the flexor carpi ulnaris (Fig.
4). The z-lengthening flaps are then outlined on the
flexor-pronator fascia. The proximal flap is based on the medial humeral
epicondyle. If there is a high origin of the superficial head of the pronator
teres, it should be included in the flap that will migrate distally (Figs.
5 and
6). The muscle flaps are then
elevated. Bipolar cautery is used to cut through the muscle, to minimize the
amount of postoperative bleeding (Fig.
7). The brachialis muscle is the deep plane at which the muscle
division stops. The common flexor tendon origin is divided completely, but the
ulnar collateral ligament is not cut and the elbow joint is not entered
(Fig. 8). The lacertus fibrosus
is then divided to permit the flaps to rotate distally
(Fig. 9). The periosteal origin
of the flexor carpi ulnaris is detached from the ulna, as this is the analog
to the medial intermuscular septum proximally
(Fig. 10). The muscle flaps
are elevated. If there is a high origin of the superficial head of the flexor
carpi ulnaris, it must be taken down completely. If there is an attachment of
this muscle to the brachialis, it must be divided. Care must be taken to not
injure the median nerve if it is in a medial location, or to divide any motor
branch to the pronator teres as the muscle flap is created. The flap attached
to the medial humeral epicondyle can be released as necessary
(Fig. 11). The ulnar nerve is
then elevated from the posterior condylar groove of the humerus. Segmental
vessels are divided, if necessary, and the nerve is placed onto the brachialis
muscle (Figs. 12 and
13). The proximal and distal
transposition points should be checked to be sure that there are no points of
constriction. Often distally, a small motor fascicle to the flexor carpi
ulnaris will need to be dissected intramuscularly to prevent the ulnar nerve
from being pulled proximally against the medial humeral epicondyle. The
flexor-pronator fascia of the two flaps should come together without any
tension. Otherwise, the fascia should be incised further. While the ulnar
nerve is protected, the two fascial edges of the flap are then sutured
together, superficial to the nerve, with three horizontal mattress sutures of
3-0 nonabsorbable braided suture material
(Fig. 14). At this point, one
finger should be able to pass easily beneath the newly constructed
flexorpronator muscle fascia (Fig.
15). The skin is closed with care being taken not to include the
medial antebrachial cutaneous nerve within the sutures.
INDICATIONS:
The indications for decompression of the ulnar nerve at the elbow are a
failure of the symptoms of ulnar nerve entrapment to decrease with
nonoperative measures and documentation that the degree of ulnar nerve
dysfunction either is progressing or has reached the point of axonal loss.
CONTRAINDICATIONS:
There is no absolute contraindication to the performance of a
musculofascial slide procedure. A relative contraindication is anticoagulation
treatment or a coagulopathy, as the muscle dissection predisposes to increased
bleeding. Primary ulnar nerve decompression would also be considered to be
relatively contraindicated for a patient, such as a musician, who requires
great dexterity for his or her vocation or avocation, as is it not clear what
effect the 1.5-cm musculofascial lengthening has on the coordination and fine
motor activity in the hand.
PITFALLS:
As with any peripheral nerve surgery, the surgeon must have a thorough
knowledge of the anatomy, be aware of the variations in the anatomy, and
utilize a pneumatic tourniquet and loupe magnification.
Internal neurolysis of the ulnar nerve should be avoided, as it is critical
to preserve the longitudinal blood supply to the nerve, especially when the
surgeon is performing a submuscular transposition in which the segmental
collateral blood supply is partially disrupted.
The surgeon should be sure to release the periosteal origin of the flexor
carpi ulnaris from the ulna, as this is analogous distally to the medial
intramuscular septum proximally.
The fascia from the medial head of the triceps to the intramuscular septum
must be released well proximally. The surgeon must be aware that there can be
an anomalous head of the medial triceps that crosses anterior to the ulnar
nerve. If it is present, it must be divided.
Finally, the surgeon should be aware that if the posterior branch of the
medial antebrachial cutaneous nerve has not been seen and protected, it
probably has been injured.
AUTHOR UPDATE:
I continue to use and have great confidence in the results of
musculofascial lengthening for decompression of the ulnar nerve at the elbow.
In my consecutive series of 653 procedures over the past seven years, no
patient has had to be operated on again. A mild elbow contracture, with a lack
of just 10° of complete extension, developed in one patient. Bruising
remains the most common complication, occurring in 5% of patients, but there
have been no hematomas requiring drainage. Six patients have required surgical
resection of a symptomatic neuroma of the medial antebrachial cutaneous
nerve.
A soft compression dressing is applied, and the tourniquet is deflated. The
tourniquet may be deflated first if there is any concern about bleeding and
the need for hemostasis. The elastic wrap applied in the operating room is
left on for the first thirty minutes in the recovery room and then is removed.
A sling is worn during nighttime and when the patient is walking. For the rest
of the time, the arm is placed on a pillow in a comfortable position and a
full active range of motion is permitted. The dressing is removed at one week,
and the sutures are removed at two weeks.