CHAPTER 55 • UPPER EXTREMITY NERVE ENTRAPMENT 327median nerve over the pronator teres muscle. Tinel’s test
may be positive, Phalen’s test is negative.- Treatment: Rest, splinting, anti-inflammatories,
and/or steroid injections into the area of entrapment.
If there is no improvement in 6 months, surgical
exploration and release of offending structure leads to
full recovery unless severe axonotmesis is present
(Eversmann, 1992).
ENTRAPMENTSITE3—ANTERIORINTEROSSEOUS
NERVESYNDROME(KILOH-NEVINSYNDROME)
- Anatomy:In the forearm, the median nerve gives off
a large deep motor branch, the anterior interosseous
nerve that supplies the flexor pollicis longus, the two
lateral flexor digitorum profundus muscles and the
pronator quadratus. Anterior interosseous nerve
lesions are rare. - Risk factors:Most discussions are case reports of
complications with supracondylar humerus fracture
(especially in children), or venipuncture. Anatomic
variants also play a role. An important differential is
neuralgic amyotrophy (brachial plexitis). - Symptoms and signs:No sensory symptoms. A spe-
cific test is the “O” sign. Patients are unable to hold,
and resist opening of an index to thumb tip to tip
pinch. The two distal phalanges align flat against each
other to hold the pinch. There is no sensory deficit. - Treatment: Usually conservative management.
Surgical exploration may become necessary.
ENTRAPMENTSITE4—CARPALTUNNELSYNDROME
- Anatomy:At the wrist the median nerve (except for
the sensory fibers supplying an area on the thenar
eminence) passes through the carpal tunnel (entrap-
ment site 4). It is formed by the arched carpal bones
covered by the carpal ligament, which spans from
the pisiform and hamate to the trapezium and
scaphoid. It contains the median nerve, the tendons
of the flexor digitorum superficialis, profundus,
flexor pollicis longus, and flexor carpi radialis. In
the hand, the median nerve supplies the lateral two
lumbricals, and most of the thenar muscles, except
for the deep head of the flexor pollicis brevis.
Sensory fibers after traveling through the carpal
tunnel supply the lateral 3^1 / 2 digits (entrapment site
5) and the lateral palm, except for a small area over
the thenar eminence. - CTS is the most common compression syndrome,
even though not always symptomatic; most often
bilateral, one being more involved than the other. - Risk factors:Repetitive motion activities ( jobs), low
ratio of depth to width (<0.70) of the wrist (Gordon
et al, 1988), hypothyroidism, pregnancy, and other
causes of excessive soft tissue swelling, cycling,
wheelchair athletics, tennis, baseball, volleyball,
violin, and piano playing.- Symptoms and signs:Nocturnal numbness, tingling,
and wrist pain. Symptoms increase with activities.
Subjects are dropping things. There is sensory impair-
ment in a median nerve distribution, and weak hand
grip. When holding a pinch against resistance, the
patient frequently will use the ulnar innervated deep
flexor pollicis to oppose the index, instead of the APB. - Treatment:Splinting, at night and during activities
that provoke increased symptoms; avoidance of con-
stant wearing of assistive device to prevent disuse
atrophy; anti-inflammatories; Pyridoxine (deficiency
often present); steroid injections surgical release.
ENTRAPMENTSITE5—DIGITAL
NERVEENTRAPMENT- Anatomy: Median nerve sensory nerve fibers are
located on the medial and lateral side of digits 1–3 and
on the lateral side of digit 4. They may become
entrapped. At risk are baseball players, bowlers,
flutists (lateral side of left index finger), violinists,
cellists (right thumb), percussionists (left middle
finger), and vibration exposure (vibration syndrome). - Treatment:Anti-inflammatory drugs and splinting
may reduce the acuteness of the syndrome. Steroid
injections or surgical release are the treatments of
choice.
ULNAR NERVE- The ulnar nerve supplies only two muscles in the fore-
arm and with the median nerve all intrinsic muscles of
the hand. There are five distinct areas of potential
entrapment.
ENTRAPMENTSITE1—LIGAMENT OFSTRUTHERS
ENTRAPMENT- Anatomy:The ulnar nerve (C8—T1) travels through
the medial cord of the brachial plexus. It accompanies
the brachial artery and the median nerve in a neurovas-
cular bundle. The nerve then passes distally, between
the coracobrachialis and triceps muscles. At the mid-
point of the upper arm, the nerve enters the posterior
compartment of the arm by piercing the intermuscular
septum. The nerve runs along the medial head of the tri-
ceps in a tough investing fascia that comprises the
arcade of Struthers(risk factor) (entrapment site 1). - Symptoms and signs:Similar to those of median
nerve compression at the same site. - Treatment:Conservative management is usually not
adequate. Surgery to release the constricting band is
often favored.