Carpal Tunnel Syndrome: A Growing Epidemic Among Dental Professionals?
Todd P. Stitik, MD
The carpal tunnel region - bounded by the carpal bones of the
wrist along the floor and the flexor retinaculum along the roof and sides - can
become afflicted with a focal peripheral neuropathy known as carpal tunnel
syndrome. This disease process involves peripheral nerve dysfunction of the
median nerve as it passes through the carpal tunnel region of the wrist. The
median nerve is surrounded by nine finger flexor tendons, which also travel
through the tunnel (Figure 1). Once the median nerve exits the carpal tunnel,
it innervates the thenar muscles of the thumb and the skin covering the thumb,
second, third, and the radial half of the fourth digit (Figure 2). Nerve
dysfunction in carpal tunnel syndrome is generally due to either chronic
pressure-induced loss of the myelin sheath covering (demyelination) and/or
acute focal block in the ability of the nerve to conduct impulses beyond a
certain site (conduction block) (Figure 3). In severe conditions, these
processes can result in the death of nerve fibers (axon loss).
Symptoms of carpal tunnel syndrome include paresthesias,
incoordination of the fingers, the rapid onset of hand fatigue and, in severe
cases, overt weakness of the hands. Nocturnal symptom exacerbation - as well as
temporary symptom relief with vigorous shaking of the hands (ie, "flick
sign") are additional pathognomic signs. Although symptom onset is
generally insidious, it can be acute and precipitated by vigorous or prolonged
use of the hands. The symptoms are, therefore, potentially intensified by the
performance of dental procedures and can significantly inhibit these activities.
Although carpal tunnel syndrome has been attributed to numerous
etiological factors,1-12 the buildup of pressure within the tunnel
and its subsequent transmission to the median nerve is a common denominator.
Several medical conditions associated with carpal tunnel syndrome include
diabetes mellitus, situations related to fluid overload, tenosynovitis, and
connective tissue diseases. Due to the swelling of the nine finger flexor
tendon sheaths (flexor tenosynovitis) as they pass through the tunnel, this
pressure can significantly increase. Swelling occurs as a result of diseases
that directly affect the tendon sheath or from repetitive activities that
result in an overuse form of flexor tenosynovitis. Intratunnel pressure can
also escalate due to poor ergonomic wrist positions (eg, extension).13,14
Dental procedures have the potential to cause carpal tunnel syndrome via the
combined effects of flexor tenosynovitis and repetitive hand movements;
pressure increases from the occasional assumption of awkward hand positions. In
addition, the use of vibrating handheld instruments has been identified as an
independent risk factor for carpal tunnel syndrome.15,16 Dental
hygienists are believed to be particularly at risk for this condition.15,17-21
in the Dental Profession
Although the performance of dental procedures is a potential
precipitant of carpal tunnel syndrome, relatively few studies have attempted to
quantitate the incidence in dental professionals. For example, although a
survey from a population of clinicians in Nebraska estimated a 29% incidence of
"upper limb or neck peripheral neuropathy" in general, it did not
specifically address the incidence of carpal tunnel syndrome.22
Since carpal tunnel syndrome is a frequent upper extremity entrapment
neuropathy, however, this study does suggest that it potentially affects a
large number of dental professionals. Using vibration threshold testing,17
one study of 58 hygienists determined a 25.9% symptom rate and a 12% actual
disease rate for this condition.
The diagnosis of carpal tunnel syndrome is established through the
analysis of patient symptoms, as well as objective findings determined by
physical examinations and electrodiagnostic testing. Since physical
examinations are often insufficient, electrodiagnostic testing is frequently
utilized to confirm the diagnosis and determine disease severity.23,24
Various upper extremity conditions can mimic the symptoms of carpal tunnel
syndrome, and therefore must be excluded in order to confirm that a patient
suffers from carpal tunnel syndrome.
Carpal tunnel syndrome can be overwhelmingly disabling and
difficult to treat in dental professionals, since the practice of dentistry is
essentially incompatible with first-line treatment, (eg, wrist splints and
rest). Specifically, the dental professional is often unable to comfortably
wear wrist splints beneath gloves during the performance of job-related
activities. In addition, it is difficult for affected individuals to rest their
hands. Although medications that include nonsteroidal anti-inflammatory drugs
and corticosteroid injections into the carpal tunnel can be administered, these
measures often provide incomplete and transient symptom relief. A definitive
cure - surgical transection of the carpal ligament that forms the roof of the
tunnel - can be performed, but this procedure necessitates an extended absence
from work, and has been associated with potentially severe complications.25
The latter is particularly true when the procedure is performed endoscopically
rather than via the traditional open surgical approach.26
Although prevention of the condition is an ideal strategy, it is
difficult to modify the practice of dentistry to the point where its
practitioners are no longer at risk for carpal tunnel syndrome. While
contemporary literature on ergonomics has focused on back pain and dentistry
rather than carpal tunnel syndrome and dentistry,27-30 several
relevant preventive strategies have been suggested.31 As additional
information on this condition and its effects on dental-related activities are
accumulated, the efficacy of prevention strategies can be improved.
Carpal tunnel syndrome is caused by a focal upper extremity
entrapment neuropathy. Although its exact incidence in dentistry is not known
with certainty, it is a potentially prevalent condition due to work-related
factors that result in abnormally high pressure on the median nerve as it
passes through the carpal tunnel. This condition can be recognized by certain
signs and symptoms, and its diagnosis can be confirmed by electrodiagnostic
testing. Treatment of dental professionals afflicted with carpal tunnel
syndrome is a challenge, as is prevention of the condition. It is an important
issue since it can prove to be quite disabling due to the deterioration of
*Assistant Professor of Physical Medicine and Rehabilitation,
University of Medicine and Dentistry of New Jersey, New Jersey Medical School,
Newark, New Jersey.
† Private practices, Union City, New Jersey; New York, New York.
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