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55 UPPER EXTREMITY NERVE
ENTRAPMENT
Margarete Di Benedetto, MD
Robert Giering, MDGENERAL PRINCIPLES OF UPPER
EXTREMITY NERVE ENTRAPMENTEPIDEMIOLOGY- The most common nerve entrapment is that of the
median nerve at the wrist, the carpal tunnel syndrome
(CTS). Its occurrence is 3.46 cases per 1000 person-
years. Female to male ratio for CTS is about 3:1
(Kimura, 2001). The next highest incidence is entrap-
ment of the ulnar nerve at the elbow (Dumitru, Amato,
and Zwarts, 2002). Krivickas and Wilbourn (2000)
studied 180 athletes with sports injuries in his electro-
diagnostic laboratory, of which 23% had median
nerve injuries, 22% stingers, 10.5% radial nerve
lesions, 10.5% ulnar nerve compression syndromes,
12% axillary nerve problems, and 7.8% entrapment of
the suprascapular nerve only.
PATHOPHYSIOLOGY- Nerve entrapment occurs when the nerve passes
through a tight space, placing it at risk for mechanical
compression as well as ischemia secondary to the
pressure on the vasa nervorum. Persistent compres-
sion results in predictable, progressive degrees of
nerve damage, as classified by Seddon: Neurapraxia,
Axonotmesis, and Neurotmesis (Kimura, 2001).
1.Neurapraxia(conduction block) is reversible fail-
ure of conduction across the affected segment.
Eventually demyelination results. Most vulnerable
are large myelinated fibers. Duration of compres-
sion determines degree of damage. The presence of
neurapraxia can vary from minutes to months.
2.Axonotmesis specifies axonal damage, with
endoneurium and perineurium intact. Wallerian
degeneration ensues (axonal breakdown distal to
lesion). Preservation of endoneurial tubes provide
a guide for regeneration of axons. Recovery is on
the order of months.
3.Neurotmesis represents complete disruption of
axons, endoneurium, and perineurium. Wallerian
degeneration occurs. Poor functional outcome
results, and surgical intervention is usually indicated.
320 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE